tempest411

Hello,

I have an alternator torn apart, have obtained new parts for rebuild, but would like to know what the resistance should be between the four leads coming from the stator windings. It's for an early car, and I have the windings de-soldered from the diode plate. I picked up a new NOS diode plate from E-Bay and will be using that.

Thank you,

Rick

marc abrams

Rick, I once worked in a auto electric shop. The stator can't be checked with a ohmmeter. There's is a special tester just for that. It feed each lead of the stator with AC current checked for current draw and leakage. Anyhow, maybe 1 out of 15 stators where bad.

tempest411

Thank you Marc, that's beyond my capacity I think. I guess I'll just have to solder it to the new diode plate, reassemble and hope for the best.

PaulD_944S2

Rick,

I think you could at least confirm the condition of the windings.

Why don't you test the DC resistance of each winding; they should be very close to each other.
I would think the resistance would be very low.

You should also test from each winding to the frame, and between windings, for any shorts.

Other than that, if it checks out, you should be good to go.

Tiger03447

Look for breaks in the insulation varnish that coats the wires. could be a vibration issue.

konakat

Yeah, I would expect a low resistance for each stator, and a high resistance between stators. As long as you see something along those lines and they are consistent across stators, I think you are probably good.

screamin94Z

As Paul suggests, there is really only two tests that would tell you if the stator is bad and you should be able to check with a multimeter. First, check that there is not a short between coils. You should have very high resistance between coils (>100 kOhm). Resistance of one coil will be on the order of a few ohms or less.

The second test would be to test for a short from any of the windings to the housing. This resistance should be >100 kOhm as well. If you get a low resistance value then it must be replaced.

tempest411

That's interesting. There are four leads exiting the stator windings, one of them is a smaller gauge than the other three. I have neglible resistance between any pair of leads I put a meter to. That is not what I expected.

PaulD_944S2

The windings are all connected together, and are heavy gauge and not that long, so resistance will be very low.

That you have connectivity between windings is good, no opens.

Just check for shorts to the frame.

tempest411

Thank you very much for your help. I've never gotten this far into tinkering with an alternator, but I figured in light of all the other things I've got on my plate, what the heck?!