Good morning GRM forum crew!
I have be diligently trying to get my grandfathers 1970 John Deere 120 lawn tractor running and functional to use on our new property.
However I have run into an issue... we actually several issuses... but the one that has me scratching my head is this:
The 12v lead coming out of the rectifier is getting hot. Hot enough to melt the plug connector. This is what I started with, at some point ( I think my father) replaced the failed OEM rectifier with a bridge rectifier and some bodgey wiring.
Yesterday, I replaced the Bridge and jumpers with a new rectifier, and still the same problem. The stator is producing 28v AC and the rectifier is outputting 13.6v to the system, but as soon as I connect that DC lead it gets too hot to touch with in a couple minutes. Note: I have the jumper wires in for testing... but the result/problem is the same with or without them.
That light green (middle) lead is the 12v wire and it leads staight to the ignition switch. My thought is it has a short somewhere down stream... but why would it be getting that hot at THAT plug?
Anyone got ideas of what I can test/ check to track down the problem?
When we where restoring my ST/16 we redid all the wiring just so we knew it was right. There is not much there so why not?
You have a short somewhere down stream. Start looking. Disconnect the regulator wire, put an ohm meter on the switch side of it, check the resistance, start disconnecting things until it goes high.
Professor_Brap said:
When we where restoring my ST/16 we redid all the wiring just so we knew it was right. There is not much there so why not?
Ideally I would like to do a full resto on it, but that really wasn't the plan going in. We used to run this thing every weekend at my parents house, Granted that was atleast fifteen years ago. When my wife I got our new place I figured we could use it.
I cleaned the points and re-crimped the spark plug wire to get it running. Changed the dive belts and fixed the deck tensioner. Nothing dramatic, just one thing after another and I (and my neighbors) would like to finally mow the lawn completely. At this point I probably could have been farther ahead tearing it down though.
It runs like a champ, I just would like it not set itself on fire.
Dr. Hess said:
You have a short somewhere down stream. Start looking. Disconnect the regulator wire, put an ohm meter on the switch side of it, check the resistance, start disconnecting things until it goes high.
That is what I was sitting here thinking... and maybe that plug is the highest point if resistance in the line to the short?
Going to have to do alittle more searching for a good wire diagram. The 120 was only built for two years (my Grandfather had a knack for picking up oddities) but the 120 shares alot of commonalities with the 140
It states on the site for l120. Don't know for sure. Hope it helps.
At a quick glance it looks like there's something missing. It appears that the alternator output is rectified but not regulated. That matches your symptoms as well.
In reply to Dirtydog :
L120 is a newish mower. Completely different animal.
gearheadmb said:
In reply to Dirtydog :
L120 is a newish mower. Completely different animal.
Yes the L120 is a completely different animal... however that is what what the all knowing google thinks you want. Thats is why I have bern referring to the 140 stuff.
I have yet to do any more testing on it, as it has been raining almost all week here and there are other things to be done. However I got to thinking:
I am seeing battery voltage on the wire that is supposed to go from the rectifier to the ignition swtch (without being connected to the rectifier)... which seems to make sence as it should be on the positive side. So I should be able to run a lead from the rectifier to the positive battery wire, if it stays cool I narrow it down to a short down stream, if it gets hot it's something in the charging system itself.
APEowner said:
At a quick glance it looks like there's something missing. It appears that the alternator output is rectified but not regulated. That matches your symptoms as well.
I cross referenced the original JD/Kohler voltsge regulator/rectifier with what I could find online, supposed to be one unit... not saying that is right. Just what I understood.
