How to test an small electric motor

[ronniescott]

I hope this does not seem a trivial question. My car's window washer pump motor stopped working and I took it out to replace it. Being curious I did some tests before fitting a new one.

First, the circuit fuse is intact and the electrical connector to the pump motor is delivering 12 V, as expected. When I measured the resistance across the to connections to the motor it is 1 Ohm. I don't know if this is what it should be, but this is not exactly my question. Given that I = V/R, as I learned in school, my question is why the 10 amp fuse on the circuit is not blown? Also, can anyone enlighten me as to what is wrong with this pump motor?

Thanks in advance for your help.

Ronnie.

PS The replacement costs £10 so I am not contemplating a repair, this is just curiosity as to how things work.

 

[anorlunda]

Measuring the DC resistance of a motor is easy to get wrong, and it is also not helpful.

If the motor receives 12V, and if it's ground connection is good, and if the mechanical load is not jammed, then the motor is bad. I would remove the motor, and then connect the two terminals across 12V. I would also see how difficult it is to turn the mechanism by hand.