MT 372 dummy lights

[shags-72]

I found 2 broken wires on my tractor. 1 on the alternator plug and the other from the regulator plug. I fixed those and now after I start it if I turn the switch to off the charge light comes on. I thought about this and it seems like it should do this as it would indicate that you weren't charging your battery while running the tractor. Buuuut I really don't know if this is as designed. Anyone know about this? Thanks


Brad

 

[Ilikeurtractor]

The short answer is no, the charge light should not be on if the key switch is in the off position. When the switch is off power to the indicator lights is supposed to be disabled. You'll need to go through the wiring diagram to see what is going on with your wiring.

 

[shags-72]

I did not change position of the wires so what else could it be? The regulator I think is bad as it is outputting 18v with the key on. This is why I don't want to have the key on while running. I looked at the diagram and the lead from the regulator to the light is straight to it. No idea where to go from here.

 

[Ilikeurtractor]

It's probably the regulator then. It shouldn't put out more than about 14 volts DC. I need to study the wiring circuit for the alternator and regulator every time I have a problem with it (which has only been 2-3 times total on several different tractors) so I don't remember all the details. If I remember the field part though, it should only be energized when the key is on. The alternator is connected directly to the battery via the starter lug so it must be backfeeding through the regulator to the light. I'm not sure what the exact condition is that is causing your problem. I have seen one of the solenoids in the mechanical regulators have an open circuit which creates problems of course. You can test the solenoids for opens and shorts with a multimeter by opening up the unit and testing across the windings.

 

[shags-72]

Do you know if there is a regulator from like napa or something available? I have seen a few 3 wire regulators but no idea how to rewire into that. Thanks!

 

[Ilikeurtractor]

I don't know of a Napa part #. There are other vehicles that used the same regulator but I don't remember specifics. I usually just try to fix the original mechanical ones. You can replace the solenoids in them with equivalents that are fairly cheap. I see eBay lists replacement solid state ones for Satoh if you're ok with the $77+ price tag which is somewhat ridiculous.

 

[shags-72]

Youch! $77! I will see what I can come up with and maybe open it up and look at it. Could dirty connections be the problem you think. If it is I don't know how to clean the connections inside the 4 and 6 place connectors. Thanks for your help sir!

 

[shags-72]

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?

 

[PILOON]

If you are real handy you could get a GM alternator that has single wire output with built in regulator.
Recycle yards often offer them for $25-35 range.0 and auto parts would have rebuilt as well.

 

[Ilikeurtractor]

Youch! $77! I will see what I can come up with and maybe open it up and look at it. Could dirty connections be the problem you think. If it is I don't know how to clean the connections inside the 4 and 6 place connectors. Thanks for your help sir!

Anything is possible when something isn't working correctly, although dirty connections isn't one I ran across yet as a problem. Loose yes, dirty no. One of the best things you can do is acquire the service manual for your machine and read up on the electrical system and how to test it in this case if you are seeking the cheap fix and would like to learn how it works. The manual steps through some troubleshooting techniques that should narrow it down. Or you can just pick up the eBay one. It depends on how much of a desire you have to dig into stuff and how much you value what you have to trade. Some people just want things fixed so they can move on. Generally that costs money. Some people would rather try to fix it themselves. Generally that costs time, either at the time of the repair or time spent on similar prior work. You probably have an idea where you fall in those categories.

 

[Ilikeurtractor]

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?


View attachment 509785View attachment 509786

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]

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]

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]

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]

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]

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]

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]

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]

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]

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!