MT 372 dummy lights

[Ilikeurtractor]

I'm not a 100% sure on this (maybe 90%?) but it looks like you swapped the A and N wires on the alternator plug during your repairs. Swap those back and I think you'll be in business. I should have zeroed in on what has changed the first time around. For some reason I was drawn to the regulator. If something was fine before a "repair" then breaks, it almost always is associated with what was done and I missed the obvious.

Anyway, the A wire is supposed to be battery voltage and the N is about half of that when the engine is running and essentially at ground value when the engine is off. So if N is feeding the field solenoid coil (because A is energizing the light coil) in the regulator it will not pull in and reduce the field to the alternator by causing its current to go through the resistor which causes the alternator go to full voltage potential and that is the 18V you're seeing. When you turn the key off, A is still supplying voltage to the light solenoid keeping it in a pulled-in state. After that though I can't explain why your charge light is on when the key is off. I measure around 1.5V off the N line on a working circuit when the key is off (engine on,) but that doesn't seem like it would be enough to power the light. Plus, I don't see a good ground (unless the acc line in the switch goes to ground when off) going back through the light.

It's up to you whether or not you want to switch the wires back. Check them against the plug diagram attached and see what you get before swapping. Remember the plug end will be mirrored from the diagram on the attached page (A will be on the right side of the plug and N on the left looking directly into the plug)

 

[shags-72]

I don't think that is possible as I only had one wire out of the connector. Pulled the female spade out, attached the new one to the wire and shoved it back in. That goes for both. I looked at the wires connectors and the alternator. The A is definitely connected straight to the battery as it has 12+v just sitting there. Now according to the diagram it should be a white/red wire and it is. I will admit that this is the wire I fixed. I did trace it and it does go into a yellow wire as it should but when I check resistance in it that wire it goes into both coils. And holy crap it sounds when touching the body of the regulator. Not supposed to do that is it?

 

[Ilikeurtractor]

Ok so the wires shouldn't be crossed at the plug but we're getting somewhere. I'm thinking no on your question. Unplug your regulator and check for continuity on the A terminal to ground (use the regulator body for ground in this instance) in the regulator plug. It should be open/no alarm. If that checks ok, then I would take the + terminal off your battery and check the tractor side plug of the regulator A line to ground for continuity. Use the "-" terminal of the battery in this case for ground. It should be open also. If it's not, unplug your alternator plug and test it again. As a last check while your alternator and regulator plugs are disconnected, check the continuity between the A and N lines at either the alternator or regulator plugs on the tractor side. They should be open also. We've got to be getting close!

 

[shags-72]

Ok according to my diagram the IG (black) goes to body with .5 ohm and the A (yellow) wire goes to body with 23 ohms. I did this from connector to the regulator body. These are with the regulator off of the tractor and only testing the regulator wiring.

 

[Ilikeurtractor]

"A" should not show 23 ohms to the ground/body. It is going through the light solenoid and the light solenoid should only be supplied by the N wire. What reading do you get checking continuity between A and N on the regulator plug on the regulator?

 

[shags-72]

I show open between the A and N. But if I close the coil it show 100+ ohms.

 

[Ilikeurtractor]

What is the value of N to ground?

 

[shags-72]

I am checking the white wire which in my diagram is N and it shows no continuity, but if I close the coil again it is 100+.

 

[Ilikeurtractor]

A and N are swapped at the regulator apparently. I don't know how or why but that seems to be the problem. So a new regulator will fix your problem but swapping those should make your old one functional. How long have you owned the tractor? What were the symptoms that caused you to replace the connectors? When was the last time it was working correctly?

 

[shags-72]

the wires were broken at the connectors and this is the first I have noticed the problem with the lights and charging. I will give this a try tonight when I get home from work. Is there an easy way to get the female spade out of the plug? I had a hard time with this on the one I replaced.