Troubleshooting '68 Mustang: Hot Wiring and Checking Ignition System

[Big Block]

Does ayone know how to hot wire a '68 Mustang? Won't start. A burnt wire along the
ignition trail.
Also, is there a shorter, faster way to check the wiring in the ignition system (from starter relay-solenoid, to the ignition switch (which is O.K. by the way)) without peeling off all the black tape and test probing every 6"-12" for a burnt wire?
Any thoughts...

 

[Averagesupernova]

Not sure what you are after. If you know the wire from the starter relay to the switch is good then why would you need to peel it back? When you say it 'won't start', what specifically do you mean?

 

[Big Block]

AvengeSuperNova,
The problem is no power, no lights - nothing, nadda.The wires from the oil pressure gauge and the ammeter gauage were mistakenly touched- while the battery was stll hooked up. I smelt some burnt wiring under the dash and then there was no power to the ignition switch. I have checked the ignition switch and its wires and they are A.O.K.

 

[turbo]

OK, no power at all is very different from "won't start". Start by checking hot-to-ground at the battery, and work back through the fuse block(s) to see if you managed to burn a fuse. That would be the easiest fix, and that might be the most likely damage from an unintentional short. Good luck, and post back as you troubleshoot.

 

[Big Block]

Turbo-1,
I have checked all fuses, and their clip holders for continuity. Everything checks out. But what I haven't checked yet is the wiring harness that feeds into the back of the fuse box.
By the way, how do you remove the fuse box in a '68 Mustang? Bolts, clips, pop-rivets? What a pain...

 

[turbo]

Turbo-1,
I have checked all fuses, and their clip holders for continuity. Everything checks out. But what I haven't checked yet is the wiring harness that feeds into the back of the fuse box.
By the way, how do you remove the fuse box in a '68 Mustang? Bolts, clips, pop-rivets? What a pain...

I had a '67 coupe, but sadly, it rotted into scale long ago, so I don't have it for reference. I actually love trouble-shooting cars that are non-computerized, but it's tough to be much help at a distance.

 

[Averagesupernova]

Just a hunch, but you probably smoked the ammeter. Generally ALL current except for the starter goes through the ammeter. If current is going one direction (battery charging) the meter swings to charge. The opposite should be obvious. So, take a test light with the battery hooked up and start at the ammeter.

 

[Ranger Mike]

i agree ..check amp meter..Ford had a good idea by using a separate solenoid switch. 12 volt cable ran from + side of battery to the switch. another HD cable ran from the other big lug bolt to the starter motor. The switch was controlled by a smaller red green stripe 12 gauge wire running to one of the small terminals. Take a test light and check to see you got power on one side of the large lugs..if battery is ok you should. disconnect one of the smaller wires and with ignition key on, one of the wires should be hot...if not..you fried a wire..take a jumper wire and jump from hot side of battery to one of the the small terminal lugs..this switches on the solenoid relay and the starter should crank..

 

[Big Block]

Ranger Mike,
None of the small wires on the solenoid are hot...so I have burnt a wire or fuseable link.
But I have not checked the wires going into and behind the fuse box.
Do you know how to remove the fuse box (on a '68 Mustang besides very carefully)? Are there bolts, clips, pop-rivets or whatever...

 

[Averagesupernova]

By solenoid I assume you mean the relay mounted on or next to the fender. None of the wires there should be hot except the main lug that is hooked to the battery cable. One of the wires activates the starter relay and the other is a ballast resistor bypass for the points style ignition. The heavy wire going to the starter itself should be obvious. There should be one or more wires hooked to the terminal that is the main battery cable. These are the wires you are interested in. It should end up at the ammeter. Now have you done like I asked and started at the ammeter?

 

[Ranger Mike]

hopefully you both read my post...i said with the ignition key ON..check for hot wire...
specifically..the ignition switch as an On setting..radio will play..and a turn and hold position that will throw juice to the starter relay...this is the ON I am talking about..rig the tset light so you can check the wire to the relay as you are holding the ig key at the above position..should be a hot wire and there had better be one ifin you expect the solenoid/relay to work...to see if it functioning.. use a jumper wire...nuff said?

 

[Big Block]

Ranger Mike,
I took a test light to the solenoid...got power on the large lug nut closest to the +side of the battery. Turned ignition key ON , disconnected one of the smaller wires and tested it...No power. Then disconnected and tested the other small wire...No power.Tested the ammeter with the test light...No power.
But I did get power in the oil pressure guage...Also, there's no power in the radio or any lights!

 

[Big Block]

Ranger Mike,
re '68 428CJ Mustang
I am not really that good a reading complicated electrical schematics. Could you walk me threw the step by step process of what happens (the power path) in the ignition system from the time the key is turned "on" (in the cylinder) to when the engine starts cranks.

 

[Averagesupernova]

There are two smaller wires on the starter relay correct? One of them is to activate the relay to run the starter. Obviously you won't have power there until you turn the ignition switch to START. The other smaller wire is an ignition ballast resistor bypass. When the starter relay kicks in the ballast resistor is bypassed for easier starting. Ignore this wire also, it is irrelevant at this point in troubleshooting. The issue is that you don't have power at the ammeter. Although I can't quite understand why you would have power at the oil pressure gauge. You are sure you were probing the correct place? I don't know the exact path of current between the ammeter and the starter relay main battery post but I am assuming that there is a burnt off wire or opened fuse link between the starter relay and ammeter. I doubt it goes through any fuse since charging current has to go through the ammeter and at times this is quite high. Vehicles of this age didn't place fuses in this location. Also, some systems use a shunt resistor out under the hood as part of the ammeter circuit. I don't think Fords of this age did, but I could be wrong. I am probably correct in assuming you don't have power at the heavy wire on the alternator either?
-
Edit: If there is no actual ballast resistor for the points style ignition then the actual wire between the ignition switch and coil is a higher resistance wire that serves as a ballast resistor. My '65 Galaxy is this way. Also, the diagrams that Ranger Mike has posted are simplified in that they do not even show an ammeter.

 

[HowlerMonkey]

Doesn't the entire car's electrical system 12+ supply other than the starter pass through the ammeter shunt?

If so, it's path would need to be restored and the ammeter replaced.

I had this happen on a mazda rx-2 where the battery tipped over and the positive terminal touched the body on a freeway offramp and it required I replace that large positively charged wire that ran from the battery/fuselinks...etc to the ammeter.

If you want to just start and run the car independant of the rest of the electrical system, that's simple.

The starter is already independant of the rest of the car other than what triggers it and the whatever is piggybacked on it.

All you need is to supply a +12v to the positive side of the coil (after removing anything else on that terminal) and to be able to jump the starter soleniod from positive supply to the trigger or "s" terminal to actuate the starter.

That said, you have to remove any chance of further conflagration by removing all other ring terminals but the large cable from battery to soleniod and large cable from soleniod to starter

If you want more, you have to fix the issue that caused the smoke to appear.

 

[Ranger Mike]

Averagesupernova pretty well nailed it..and yes, the diagram i posted does not show an amp meter. And it soinds like you did smoke the wire on the amp meter.. let us concentrate on basic automotive trouble shooting...you have 12 volts at the battery..this has been confirmed. I was taught to always work from power out backwards to power in. Di you use a jumper wire from the hot side of the battery to the starter terminal lug of the starter solenoid / relay?

 

[Big Block]

Ranger Mike,
Recap-
With a test light I have checked for power on the following:
. large lug nut on solenoid (closest to +side of battery)...got power!
. disconnected smaller wires on solenoid, turned ignition key to ON then START...no power!
. with a jumper wire, jumped the hot +side of the battery to a small terminal lug...a few clicks from the solenoid, then nothing - that's all she wrote!
. heavy wire on the alternator...no power!
. ammeter...no power! (By the way, Is there a ground wire attached to the ammeter guage?)
. oil pressure guage...got power!
. fuses and ignition switch...O.K. for a continuity check!

??

 

[turbo]

No ground-wire needed to ammeter gauge, since the body of the gauge is metallic and is connected to the body of the car (negative ground). If the connection is badly corroded, there could be a loss of conductivity.

 

[HowlerMonkey]

It's possible your car was seeking engine/starter ground through the ammeter circuit.

Take a set of jumper cables and both on one end to a suitable metallic part of the engine.

Hook one of the other end on the negative battery terminal and the other one to a bolt for the chassis.

What this does is guarantee you have both engine and body ground.

If jumping the starter soleniod does not actuate the starter, your +12 from the soleniod to the starter is bad or the starter itself.

 

[Ranger Mike]

the good news is that you have clicking sound at the solenoid..
probably bad solenoid..which is relatively cheap fix..but to confirm

disconnect the large battery cable from the solenoid and and touch it to the larger cable running to the starter. if the starter spins you have a defective solenoid..if it does not it is a bad starter.
we have to back track the wiring after this but we are making progress so hang in there..

 

[Averagesupernova]

I think you have a combination of problems here. I agree with Ranger Mike about bypassing the starter relay to see if the starter will actually turn. If that happens it proves the battery and connections are good. I don't think there is any chance of starter ground current going back through the ammeter circuit. Think back to what caused this in the first place which is something touching the ammeter wire as well as a couple of other wires. Smoke was released indicating excessive current in the area smoke was released. If you didn't have power at the ammeter I wouldn't have expected you to have power at the alternator. That is a good thing in that it makes sense to me. Start at the ammeter and trace back to the battery from there.

 

[Big Block]

HowlerMonkey,
Could you be more clear and specific about your battery cable connections...

 

[Big Block]

Ranger Mike, and Averagesupernova,
I have disconnected the large battery cable from the solenoid lug - but left the other 2 wires attached to the lug.
With a jumper wire (attached to the prevoius large battery cable), I touched the larger cable (attached to the other lug on the solenoid) running to the starter. Nothing...
I'm installing a new solenoid tomorrow and getting the ammeter checked out. Can an ammeter be rebuilt?
Q: Will I blow this new solenoid because of the current wiring problems?

 

[AlephZero]

the good news is that you have clicking sound at the solenoid..
probably bad solenoid..which is relatively cheap fix.

Every time I have had a clicking sound from the starter solenoid (probably about 4 times in 40 years, on different cars) the cause has been a poor (corroded) Earth connection, usually where the the battery Earth strap is bolted onto the car bodywork. Or, the battery has failed or is flat, and it can't deliver enough current to hold the solenoid and turn the starter at the same time.

Solenoids are more or less indestructible IMO.

Step 1: recharge the battery and try again (especially considering you said you shorted it, at the start of this collection of problems!)

Step 2: clean up the Earth strap connections and try again.

 

[Averagesupernova]

What are you using to test for power at various points on the vehicle? A test light I assume? If so, when you do your checks under the hood, don't ground it to the negative battery post. Ground it to the chassis or fender of something. Ideally, ground it to the same place for ALL tests including the ones under the dash. A bit impractical of course, but might relieve some confusion.

 

[Ranger Mike]

i can see this is going to be a back to basic post

 

[Ranger Mike]

so here you go

 

[nucleus]

When you shorted the wires together you likely melted the wire insulation or burned some pins in a connector. Regardless it appears that you are getting a circuit from the wire to the battery side of ampere gauge and its finding ground through the oil pressure-sending unit. This is giving a large parasitic draw and your battery has drained. The reason I believe this is your starter solenoid making a clicking sound and your lights not coming on– both symptoms of a weak battery.

Before continuing you should take your battery out and get it charged, then reinstall and try to jump the solenoid. But be sure to disconnect the negative lead from the battery as soon as you are finished because it will continue to drain the battery until you find and fix the damage from the smoking wires. BTW if you had disconnected the negative lead from the battery before you started playing with the wires the smoke would not have happened, but you live and learn.

When removing the battery UNDO THE NEGATIVE FIRST AND RECONNECT THE NEGATIVE LAST. Here’s why:

http://7faq.com/owbase/ow.asp?GoodEngineeringPractice%2FBatteries%2FDisconnectingTheBattery

It would likely help if you had the proper wiring diagram. There is a part of one for amp gauge one here:

http://mustangforums.com/forum/classic-mustangs/596726-amp-gauge-wiring.html

 

[Big Block]

Got a new starter solenoid. Give me a couple of days and I'll post back with a progress report. Thanks guys...

 

[Big Block]

I'm back...as Arnie would say.
CORRECTION:
This is not an ammeter guage - it's an alternator guage, which the guys told me, and say that the gauge must be tested in the car. Brilliant guys...How do I test an alternator gauge in a car that won't start because it has no power(juice)!
THE TRUE STORY-
After changing my stick shift, I mistakenly touched either the alternator gauge wire and the oil pressure gauge wires together, or grounded one of them (doesn't really matter...don't remember now anyhow)-while the battery was still hooked up. Then I smelt some burnt insulation and thought I saw some "whitish" smoke (under the dash, to the right of the steering column and above the gas pedal). I troubleshooted for quite awhile, but came up with nothing. My back was killing me, so I got this kid helper down the street to connect the alternator and oil pressure guages wires (according to my instructions). But a problem could arise here because both the heavy wires are black! I tried starting the car-but nothing...No power, no lights, no ignition, no spark - dead in the water...
PROGRESS REPORT:
1) Got a new solenoid...Don't know if alternator guage is "dead or alive"? Is there a way of testing it off the car?
2)Remember me mentioning the oil pressure gauge had power with the test light. I found this odd so I checked further, and sure enough the wires had been switched (by the kid helper - alternator gauge wire to oil pressure guage, and oil pressure gauge wire to alternator guage. I was furious. That meant when I tried to start the car the wiring was in this messed up cross-over configuration. No power...Nothing. I have now wired it properly.
3)With ignition key ON in START position, and a jumper wire I jumped the hot large lug side of the solenoid to the "S" smaller terminal of the solenoid...Results = a couple of strong clicks from the solenoid(but no cranking). All other testing with the new solenoid has resulted in nothing...no noise...not even a whisper...

 

[Averagesupernova]

First of all, no matter what the 'guys' told you, it is in fact an ammeter gauge. I googled for images of a '68 mustang dash cluster and there is a needle that shows charge in one direction and discharge in the other direction. This IS an ammeter. Other than it's obvious function you can think of it as a piece of wire. So now that you have it hooked up right do you have power in places that you didn't before like you should? For instance heavy wire on the back of the alternator and etc? Head lights work? When the ignition switch is on do you have power at the distributor/coil? Do you get the starter relay to click with the ignition switch or just the jumper wire? You did some work on the shift mechanism. What about a neutral safety switch? It should have one or at least have had one at one time. If the starter relay is just clicking I would say you may have an issue with the starter if all the other wires are hooked up. Brings up the next obvious question. You say you did some shifter work. Was the transmission out of the car? Usually requires removal of the starter if you did. Everything hooked up right on the starter? If you haven't figured it out, I used to do troubleshooting over the phone on vehicle electrical systems. There isn't much I haven't heard.

 

[Ranger Mike]

that is great news...almost home..

Is the battery good/ How old is it? are the battery terminals corroded? Are the cables new looking? You have a strong click at the solenoid so the next step is to take a very heavy duty jumper and jump from the plus side of the battery to the heavy duty starter cable bolted to the solenoid..if you have a large spark but no starter spinning.. the starter is fried..
but...the battery and battery cable to solenoid and cable tot he starter must be good,

 

[Big Block]

Ranger Mike,
Battery is good and strong 12.48V, is new and the posts are clean. Cables are newish with no nicks...They're good.
Next I'll post the results from your solenoid test.
Q:
Do you, or do you know anyone who has "diagrams" on exact locations of all fuseable links pertaining to the ignition and starting system in my car?...

Averagesupernova,
. The starter is brand new but hasn't been started in 6 months.
. My car is a 4-speed manual shift and doesn't have a neutral safety switch (automatics only).
. I changed the stick shift mechanism only...Never touched the trani or starter.
. No headlights and no radio.
. I will check power with ignition key ON to the distributor/coil snd post back the reults.
Q:
Maybe it's a burnt fuseable link somewhere under the dash?

 

[Averagesupernova]

I will once again tell you to start at the ammeter. Since you HAD power on the oil gauge before you corrected your kid from down the streets mistake, I am assuming now that the wiring has been corrected you have power on at least one side of the ammeter. If you have power on one side of the ammeter but not the other then you have fried the ammeter. Work on getting power to the headlights and everything else first then worry about the starter. It seems to me like the starter only clicking issue is a separate one from no power to accessories. I don't know where fusable links and things are physically. Sorry, not able to help you there. The battery side of the ammeter only should hook to the battery and nothing else. The other side will hook to everything else including the heavy wire on the alternator. It is likely if you did blow a fusable link that you only cooked one, not multiples. I doubt there is any fusing between the ammeter and the alternator.

 

[hypatia]

I say you just give the car to me.

 

[Big Block]

Averagesupernova,
Thanks for the info...and I will find this burnt sucker!

Ranger Mike,
Results from jumping the "+"(positive) side of the battery to the heavy duty starter cable on the large lug of the solenoid = a small spark (but no cranking of the starter).

Where do I go from here guys?...What do I inspect next?...

 

[nucleus]

Where do I go from here guys?...What do I inspect next?...

Do a Voltage Drop Test. It is by far the best test for a starter circuit.:

http://www.sacskyranch.com/voltage.htm
http://www.youtube.com/watch?v=XhRPLgH6uZg&feature=related
http://www.youtube.com/watch?v=ry68G0C2Fyc&feature=related

Goggle it for more information.

Re your ammeter . The black lead for the oil pressure comes from the instrument voltage regulator. You may have fed 12 volts to your gauges, Do any of the gauges work?
The wiring diagrams are available here:

http://www.themustangshop.com/resources.cfm

 

[Ranger Mike]

the above video is good..you should have a huge strong spark when you jumped the battery to the starter cable..i would check the starter cable ..especially at the starter connection..make sure it has not frayed or loosened up in the wire lug that is on the end of the starter cable...worst comes to worst..pull the starter and have it checked at NAPA or Autozone...

 

[nucleus]

“My car is a 4-speed manual shift and doesn't have a neutral safety switch (automatics only).”

That does not mean that the switch is not there. On manuals the neutral safety switch has to be jumped permanently. There is a Red-Blue wire running from the S (start) terminal of your ignition switch to the starter solenoid. This wire goes through the neutral switch. You should get power when the key is held in the start position. To bypass the key you run a jumper wire from battery side of solenoid (large wire) to the small lug where the Red-Blue wire goes on. Warning: make sure car is in neutral, park brake on and disable ignition.

“Battery is good and strong 12.48V”
Just because it has 12.8 volts does not mean it’s good. Measure across the battery posts under load. For instance, when you try the starter, the voltage should not drop below 9.6 volts. If the car hasn’t been started in six months there is a good chance it will not have enough juice to turn the starter. It may not be the problem but at least you eliminated it.

 

[Averagesupernova]

All this advice is good but I think we should start where the smoke got loose. Something burned under the dash. It doesn't matter if the battery isn't good enough to spin a starter at this point. We know it was good enough to burn a wire off or open a fuse link or toast the ammeter and my assumption is that it is still that good. When we get power to the accessories and headlights we will at least know that a large portion of the cars electrical system is working.

 

[Big Block]

Averagesupernova,
You're right on the money. My alternator gauge is smoked. Got a live reading (from the test light) on the lug nut with the heavy duty alternator gauge wire, but nothing from the other lug nut.
I have to order a new gauge from the States. It will take some time to get here, so I will post back in a couple of weeks with all the other suggested "tests" results.

 

[nucleus]

According to the wiring diagram from themustangshop that I posted earlier, there is a yellow and a red wire going to the ammeter. Both of these wires go to the same plug (different terminals) then both end up near the battery side of the starter solenoid. They do not connect to any other wires.

It was the black wire that you said was crossed with the oil pressure wire and did the damage, so it had power then! Did you forget to install it when you had the wires off the starter solenoid? If not you should trace the wires back to see why you have no power.

It sounds like all you have is a test light, is that correct? With an ohmmeter you could disconnect the battery and read across the ammeter and check it before ordering a new one.

 

[nucleus]

Actually you should only get power to one terminal of the gauge at a time. With the engine not running the power should be on the black wire (with reference to ground). The yellow wire finds ground eventually through the ignition switch and some accessory, so I think it is normal to only get power on the black wire with engine off.

With the engine running the yellow wire will be more positive than the black. The black will then be the ground.

Re measuring across the gauge with ohmmeter you need to remove one lead. An ampere gauge is really a millivolt gauge connected to a shunt.

 

[Averagesupernova]

Nucleus, if there are large heavy wires that attach to the ammeter gauge, then the shunt is internal the same way it is on a multimeter. You should never ever ever ever ever have power on one side of an ammeter and not on the other. If this is the case then the ammeter is toast. Getting power through an ammeter of any kind only requires that the shunt is intact whether it is internal or external. It does not matter if the 'millivolt gauge' as you call it is even in circuit. Nucleus, so far I think you have only confused the OP.
-
To the OP: Now I realize that by my saying this questions my earlier advice but if I were you I would temporarily bypass the ammeter to make double sure so you don't needlessly purchase a new gauge. Bypassing the gauge should make your car work like it has a new gauge, but obviously the gauge won't read anything. Not only that, you can proceed to trouble shoot anything else you have wrong on the vehicle while bypassed. Just my 2 cents.

 

[nucleus]

Averagesupernova
“You should never ever ever ever ever have power on one side of an ammeter and not on the other.”

That is not what I said! I said it seeks ground through the yellow wire when the engine is not running. However, there are several paths involved, including the key being on for some of them. You will not be able to read the this power with a test light and may change the gauge for nothing.

“Nucleus, so far I think you have only confused the OP.”

I don’t think that is possible. The OP has not answered any of my questions so I doubt he/she has even read them. I feel like I am talking to myself! He needs to find someone that knows how to trace wires or he will just keep changing parts, and that can get expensive if you have to order them in.

The first wire to trace is the BLK-YELLOW from battery. It ends up at a fuse, which if open, will prevent door lights and courtesy lights from working. I agree with you re bypassing gauge for now.

 

[Averagesupernova]

Actually you should only get power to one terminal of the gauge at a time.

So what did ^^^^^^this^^^^^^^^ mean? If you have power on one side of an ammeter and not the other then the gauge is toast providing it has an internal shunt, and if external, then the shunt is fried. There is no more to this story. A test light will show this up easily. The question is if it is an internal shunt or not. I suspect after looking at the diagram that it is an external shunt. Yellow wire #37 in the diagram. There still is really only one path and that is through the yellow wire. I am suprised that they used a heavy wire to the gauge itself if it is an external shunt. OP, I hope you are watching this.
-
What are you calling the black/yellow wire that ends up at a fuse? If it is what I think it is, this is not a fuse. Cars of this era didn't usually have any fuses in the charging system or directly off the battery. There were fuses for accessories and lights but that's about it. Not even for the ignition system.

 

[Big Block]

Averagesupernova
The OP has not answered any of my questions so I doubt he/she has even read them. I feel like I am talking to myself!

This is your OP speaking Nucleus. By the way, what does OP mean?...Other Person? Other Party? or Outside Party?...Please clarify. I was waiting for the mud to settle before speaking with you.

This is the wiring setup to the alternator gauge and the oil pressure gauge as it stands now.
1) ALTERNATOR GUAGE: Looking at the back of the gauge in a normal upright position -
Left lug/post = small red and violet wire Right lug/post = heavy duty "live" black wire
Bottom lug post = a ground wire

2) OIL PRESSURE GUAGE: Looking at the back of the gauge in a normal upright
position.
Left lug/post= heavy duty black wire Right lug/post = small black wire
Bottom lug/post = a ground wire

Is this setup correct?
O:
What reading in ohms should I get when measuring across the gauge with an ohmeter(after I've removed one lead?

Averagesupernova,
Q:
How do you bypass the ammeter making my car work like it has a new guage? (posted in your 2nd last message at 11:21 AM)

 

[Averagesupernova]

Bigblock, do you understand the drawing in post number 4 in this link: http://mustangforums.com/forum/classic-mustangs/596726-amp-gauge-wiring.html
?

I think nucleus and I have come to the conclusion that it uses an external shunt. However, you still should show power on both sides of the ammeter. The yellow hilighted wire in the drawing is considered the shunt and the gauge in your dash measures the voltage dropped (lost) in that section of wire. Seems impossible at first but it is so. You should be able to see from the drawing that the gauge itself is not required for your vehicle to operate. I may have slightly misinformed you in the past and am sorry for that. So can you see how the yellow hilighted wire could cause what you are experiencing if it were burned off? The logical place to start of course is under the dash. However, the smoke you seen from under the dash could have come from the gauge AFTER the shunt was burned open under the hood. I would think this would put a full 12 volts across the gauge in your dash and could cause damage.
-
Would you agree that disconnecting the main disconnect connectors shown on the diagram should NOT cause a loss of power at the main alternator lug? Maybe you should do this and troubleshoot from there? It would be a bit easier to keep it straight in your own mind knowing to ignore everything under the dash.
-
BTW, OP means original poster.

 

[Big Block]

Averagesupernova,
Q:
How do you bypass the ammeter making my car work like it has a new guage? (posted in your 2nd last message at 4:03 AM)

Averagesupernova and/or Nucleus,

1) How do I bypass the ammeter gauge to make my car work (without the ammeter).

2) Is the below posted literal description setup of the wiring for the ammeter, and oil pressure guages correct? Please verify...

Nucleus,
This is the wiring setup to the alternator gauge and the oil pressure gauge as it stands now.
1) ALTERNATOR GUAGE: Looking at the back of the gauge in a normal upright position -
Left lug/post = small red and pale violet wire Right lug/post = heavy duty "live" black wire
Bottom lug post = a ground wire

2) OIL PRESSURE GUAGE: Looking at the back of the gauge in a normal upright
position.
Left lug/post= heavy duty black wire Right lug/post = small black wire
Bottom lug/post = a ground wire
Is this setup correct?

Nucleus,

I will do the "Voltage Drop Test" and your other tests as soon as we clear up this ammeter issue first.

1) How many ohms should I read when testing across the ammeter lug/posts (with one lead removed...WHICH LEAD?..and is the battery is NOT hooked up?...

 

[Averagesupernova]

I think you have missed the point. I clearly stated that you don't even need the gauge installed for your vehicle to work if the system uses an external shunt which nucleus and I have come to the conclusion that this is the case. I may have misinformed you earlier while thinking that there was no external shunt and that ALL the current has to pass through the gauge itself and am sorry for this. The test that shows power only on one side of the gauge is still a valid test and indicates something is open somewhere. I cannot tell you if your description of wire colors is correct. I can only go by what I know from experience and what is drawn in the link that nucleus was nice enough to post. So if you are willing to agree that the drawing I refer to is valid, can you see why I ask you to forget about what is going on under the dash for the moment and look at the hilighted yellow wire in the drawing in the link? http://mustangforums.com/forum/classic-mustangs/596726-amp-gauge-wiring.html
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Do NOT bypass the gauge itself under the dash. One wire that connects to it is not heavy enough to carry the load based on your description of said wire. You need to be concerned with the yellow hilighted wire in the diagram.
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If you need more explanation on something I've posted just ask. If you don't understand why the gauge is not needed just say so. No harm in not knowing something, we know you came here for a reason.