YM155D need some help with electrical

[jcimob]

Background....bought this tractor a few months ago, people who sold it said they had put a new battery in it. I have used it on several occasions, always started and ran fine. Then the other day, I was using it and happened to stall the engine, turned key to restart and nothing. I thought perhaps battery/battery posts, and looked, and found the battery positive to ground. I can see how they made the mistake, the short ground wire to the battery is red. The one to the starter is black. I just can't believe it was running fine like that. I checked the manual to be sure it should be neg ground, yes, so swapped it around. Still nothing. Tried to jump it from my car, nothing. So then I noticed 2 wires (green corrosion on copper) located down low close to starter, that looked like they were broken off something. Both are short and come from connectors that come out of the wiring harness, one is yellow and one red. I looked and saw one coppery green piece hanging from a bolt on side of engine (it disintegrated as soon as I touched it). As I touched these wires there was a spark, so determined red one was hot, so it could not have been tied to ground bolt on engine, so suspect the yellow one should be there, but cannot see where the red one should go. I touched the red one to the starter and it energized the starter. I looked at the wiring diagram but still am not sure where it goes. So I am hoping someone can help. I have a few questions.....
It seems there must be no power at the key, or it should still turn the starter. So that is one problem. Where the broken red wire should go is another. And what damage has been done by battery being installed wrong is another.
thanks
Frank

 

[jcimob]

A little more info........ tried as best I can to follow the circuit diagram and have come to the following conclusion....if the generator is the unit right behind the rad fan, then I suspect the yellow and red wires which are corroded off go to the generator. I thought the corroded piece of wire hanging below an engine bolt was under the bolt. Now I am reconsidering that. I see what appears to be a black sleeve coming from under what I think is the generator and going right below a bolt. On the other side right under that bolt might be where these wires went (passed through the steel below the bolt??). If so then inside that black sleeve might be the red and yellow wires that go from the generator, the red to the starter post, and the yellow to the current limiter. Seems to be the only option....there is only enough length on the broken/corroded off wires to reach that point and I see no other possible place. Hope someone can look at theirs and confirm.
thanks
Frank

 

[BobRip]

A little more info........ tried as best I can to follow the circuit diagram and have come to the following conclusion....if the generator is the unit right behind the rad fan, then I suspect the yellow and red wires which are corroded off go to the generator. I thought the corroded piece of wire hanging below an engine bolt was under the bolt. Now I am reconsidering that. I see what appears to be a black sleeve coming from under what I think is the generator and going right below a bolt. On the other side right under that bolt might be where these wires went (passed through the steel below the bolt??). If so then inside that black sleeve might be the red and yellow wires that go from the generator, the red to the starter post, and the yellow to the current limiter. Seems to be the only option....there is only enough length on the broken/corroded off wires to reach that point and I see no other possible place. Hope someone can look at theirs and confirm.
thanks
Frank

Can you take a picture of the circuit diagram and attach it. That would help. Wow, it ran with the battery in backward. Amazing. My guess is this really loaded the alternator and burned out the wiring. Maybe the alternator is OK, I just don't know. I would check the diodes for open or short (with multimeter) and the coils for signs of heating, open, and leakage between coil and ground (with multimeter).

 

[swedish-fish]

jcimob,
You got me curious and I went and checked my 155D. Here's some pictures that may help you. You're right, the little generator is enclosed right behind the fan and should have a red and yellow wire going to it. In my case, someone re-wired it to blue, but there's evidence that it was once red. Hope these help.

Also, I replaced the fuses with automotive type so you can ignore that part. In addition I wired to directional switch to some LED double faced marker lights on the fenders. Throw the switch one way and both lights come on. The other direction and they both flash. Incidentally, that little alternator is only 8.5 amps which is why I opted for low draw LED lights.

Good luck!

 

[BobRip]

What does the current limiter do? I would check that out since the reversed battery would try to pull double current through the generator.

 

[jcimob]

thanks guys (appreciated your pictures Swedish-Fish, not sure why I don't have the same harness coming from the generator but the pics confirmed to me that I was on the right path)
I finally decided to cut through the black sheath coming from under the generator right where it passes through the metal frame underneath an adjacent bolt. There were 2 wires inside, yellow and red, which are the 2 colors of my corroded/broken off wires. It is going to be a pain soldering onto them since the wire sheath is so short, barely 4-5 inches long right underneath the generator, but I should be able to do it. Was going to try tonight but after a 12 hour shift working and fading light, decided to wait for a day off and maximize my chances of success. I will have to check for damage to the diodes I guess, what with the battery being installed backwards. I assume there are parts I can access from somewhere. I know about Hoye Tractor, but wish there was a Canadian outlet to save me the cross border shipping and duty. If anyone knows of one, please let me know.

 

[TedLaRue]

Originally Posted by jcimob
I will have to check for damage to the diodes I guess, what with the battery being installed backwards.

Frank,

According to the wiring diagram, you have a generator (not an alternator). You won't find any diodes to check. Generators produce DC, so diodes aren't necessary.

 

[TedLaRue]

What does the current limiter do? I would check that out since the reversed battery would try to pull double current through the generator.

Based on the wiring diagram, I think the current limiter is a solid-state device which controls the amount of current fed to the battery by the generator. It probably senses battery voltage at the red wire, and as that voltage rises closer to 14.4 volts, it probably cuts the current to the battery to a trickle by limiting the flow of current from the ground through the generator to the battery. This has the same function as the older "voltage regulator".

If the battery were connected with reverse polarity, I think the current limiter would either shut down (many circuits have protection built in) or burn up, or would continuously supply the battery with the maximum charge current. This continuous maximum current could have cause the generator wires to burn up.