Ohm readings on a 3 prong clothes dryer

[Stephen Tashi]

TL;DR

What are the typical ohm readings across the prongs of a plug on an unplugged 3-prong clothes dryer?

What are the typical ohm readings across the prongs of a plug on an unplugged 3-prong clothes dryer? - if such typical values exist.

I bought a used electric clothes dryer (Maytag Model MEDP576KW1 ) that I haven't plugged in yet. The seller is a reliable local business that says it works. When I measure the resistance between pairs of prongs on the cord, I get, as expected, an open circuit between the two hots and between the neutral and one of the hots. But the resistance between the neutral and the other hot is 127 ohms. This doesn't change when I fiddle with the controls on the dryer.

I took similar measurements on a working dryer that I unplugged. I get the same open circuits. Between the neutral and one of the hots, I get 17 K ohms. When I press the start button, it drops to 2 ohms.

 

[Baluncore]

127 ohms would be expected across a power supply, before it starts.
17k ohms, dropping to 2 ohms, is a standby power supply, with an inductive fan or motor being connected when switched on.

Without mains voltage being applied to the appliance, it is unpredictable what resistance to expect. Check the circuit breaker rating for the outlet is sufficient, plug it in and switch it on, with a little caution.

 

[berkeman]

I did a Google Images search on Maytag Model MEDP576KW1 schematic and got some good hits (I think). Check out the hit list to see if these help...

https://www.google.com/search?clien...cUVBLMQjJkEegQIIRAC&biw=1271&bih=768&dpr=1.09

 

[Stephen Tashi]

Check the circuit breaker rating for the outlet is sufficient, plug it in and switch it on, with a little caution.

I will as soon as I solve another problem - the power cord on the dryer is 3-prong and the receptacle for it is 4-prong. I debate whether to change the receptacle and leave its ground unconnected or whether to change the cord on the dryer. The dryer was not designed for a 4-wire cord, but it looks possible to ground it. My readings find only one connection point between the neutral and the chassis. It is at the terminal (temporarily disconnected) on the left in the photo

. The terminal is on the end of a white wire that is part of the dryer's wiring, not part of the cord.

 

[Tom.G]

See page 7 of the installation manual at:
https://www.maytag.com/content/dam/.../installation-instructions-w11407405-reva.pdf

The existing wiring with the 3-conductor cord uses the Neutral of the 120/240V supply for a Safety Earth Ground. As a potential safety hazard,

THIS IS NOT ALLOWED IN MANY JURISDICTIONS.

The existence of a 4-prong outlet suggests you are in one of those jurisdictions.

Please get an electrician to install a 4-conductor cord/plug, and show him the manual page 7 for required internal wiring changes.

Cheers,
Tom