MT 372 dummy lights

Ilikeurtractor · May 17, 2017

shags-72 said:
I just pulled the regulator and it is clean as a pin inside. Contacts don't look burnt at all comparing them to burnt points I have replaced before. But I can't really open them far to really see. What do you think?

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Regulators usually stay pretty clean inside if the cover gasket is intact. Just another good reason to repair them. Clean and properly functioning aren't always related though of course. An open coil is probably as likely to occur in either case. I still have a functional regulator that lost it's cover years ago. Looks much dirtier than yours. I'm actually surprised it still works.

shags-72 · May 17, 2017

I had thought about that because really if you take away the 4 wires feeding the regulator the alternator really only has the battery wire and smaller feeder wire and the dummy light wire. I will see if I can figure out what is going on with this thing and keep that as a last resort. I found a replacement regulator and ordered it but I will mess with the one I have and test it.

shinnery41 · May 17, 2017

I cannot tell for sure from the photos but the one open coil with fine wires almost looks like it has been overheated in the middle. If you see any signs the varnish coating on the wire has overheated and bubbled or disentegrated you could have a shorted turn in the coil and it is all she wrote for that solenoid coil.
Bryce

shags-72 · May 17, 2017

I think I know the answer to this but not 100% on it. If the winding is shorted would it still be a closed circuit? It alarms on my multimeter testing for resistance.

Ilikeurtractor · May 18, 2017

Yes. You want to test for a resistance value, not continuity (alarm.) I've attached my notes on the regulator page for your reference. Unfortunately I see I did not note the resistance values for each coil but if you apply the voltages I have listed in the notes to the associated terminals it should narrow down the problem. I would recommend making sure there are at least 10 ohms resistance in the light and field coil circuits so you don't over-amp your power supply when testing if there is a short. Most power supplies protect against this anyway. You may need to energize the light coil before testing the field coil to complete the field coil circuit unless you bypass the light coil circuit internally.

Ilikeurtractor · May 18, 2017

I snapped a quick shot of the regulator that came with a S370D I have. I don't understand why a person couldn't take the 30 seconds to reinstall the cap. Guess it doesn't matter as it worked as long as they needed it (and still working.)

shags-72 · May 18, 2017

Thanks for the document and I can't believe that is still working! I got home late so I won't be able to work on this till this weekend. But I will keep you updated. Not sure when I will get the new regulator.

shags-72 · May 19, 2017

Ok I think one of the coils is burnt. One was 23 ohms or so and the other is .5 ohms and I think that is the shorted one. You did put the resistance values on the scan. They were 35 and 10 ohm. What do you think bad?

Ilikeurtractor · May 19, 2017

There are resistors in the circuit which are on the bottom side of the regulator - at least that's what I seem to remember and it makes sense. Sorry I'm being lazy now and not wanting to go find one to check. The 35 and 10 are not the values of the coils. I'm not sure what connections you're using to check resistance. Measure it from "A" to the other side of the regulator solenoid coil which will be somewhere under the cover which you removed and post what that value is. Do the same from "N" to the other side of the lamp relay coil which should be the same as ground. They may be the same values you listed in your previous post. I just need to verify and post which is which. The coils don't draw many amps to function so the resistances should be much more than .5 ohms. If it truly is .5 ohms, I would classify it as a shorted coil. You can replace it with a 12VDC plastic square one from Radio Shack (if you can find one still open) or your favorite electronic components supplier.

shags-72 · May 20, 2017

I was checking between the 2 wires from the coils and had the vom on the 200 alarm mode. and it showed .5. You are doing me a great favor sir and I greatly appreciate you time and responses!