I have an MF85 tractor and last week I was using it to pull some logs. Out of the blue it quit starting. I would push the start push button and nothing would happen. The first thing I checked was the start solenoid so I pulled it and tested it on the bench. As suspected, I put 12v to the start terminal and it did nothing so it confirmed my suspicion.
I picked up a new solenoid at an auto parts store that seemed to be a match as it looked exactly the same.
I installed it in the tractor and no luck, still doesnt work.
Ive been troubleshooting with a vom etc and nothing is making sense.
The weirdest thing is that the start terminal on the solenoid is now always hot. I would think that if there is power at that terminal the solenoid would be engaged but it isnt.
I ohmed from the battery terminal on the solenoid to the start terminal and I have continuity so thats why its always hot.
One time I worked on an old Ford tractor that had a Ground Positive system. My tractor is not Ground Positive but I wonder if those systems use a different type of solenoid?
Maybe I got the wrong type of solenoid?
The system consists of a key switch, a push button switch that should engage the starter and a neutral switch thats on the transmission to insure its in Neutral before you can start.
Ive checked all of those with a VOM and as far as I can tell they are all functioning correctly.
Any ideas as to whats going on?
Any help will be much appreciated.
Tom
You could be reading 12vdc with your vom but still have a resistance (dirty) connection that will not allow the current draw (amps). Also check that ground connection at both the battery & frame. All of that is assuming that your battery doesn't have an internal problem. You have a gremlin.
FPP ,I've found over the years that a simple test light is all that is usually needed for most equipment troubleshooting. A Voltmeter doesn't pull any amps and will sometimes show voltage when there isn't enough to do anything. Over the years I used my test light a lot more than my voltmeter and found it made troubleshooting a lot easier. Sounds like you may have a ground problem.
If start terminal on solenoid is hot and you have continually between big hot post and start terminal maybe start button provides a ground to ground terminal on solenoid to engage it . I can't recall ever seeing anything wired that way but it's possible.
Thanks for the suggestions.
I worked on it some more and after pulling the new one back out I found that the base is stamped in tiny text 6V, so its the wrong voltage. The old 6v tractors were Ground Positive so I think that might be why it has the continuity between the 2 posts. Either way I'm not going to dwell on it at this point.
I dug around and found an old start solenoid I had laying around from another machine. The posts arent positioned right to use permanently, but I figured it was good enough for a test.
I hooked it up and it works exactly as I would expect.
Now I just have to get another start solenoid.
Live and learn.
I told the guy at the store it was from a tractor and he asked 6v or 12v. I said 12 but still ended up with a 6 v.
I should have examined it closer before leaving the store.
The one I need is like a Standard SS581T except that one is 4 post. I'm not finding any 3 post versions on line so thinking maybe it going to be hard to get.
In order to use the 4 post instead of 3, I think all I need to do is ground the extra post?
Wlmedley, actually yes, I also use a test light. Its one with a ground wire and clamp with a probe.
I use it often as well as a VOM.
FPP I believe you are correct regarding grounding the fourth post. Just went through that on my mill. Broke a terminal off the solenoid taking it apart to clean the connections. Happened to be a 3 post on there. They wanted $125 for a replacement. Dug around and had a new one in my electrical box that was a 4 post. Hooked it up and didn't do anything. Ran a ground to the fourth terminal and worked like a charm.
https://www.reliableaftermarketparts.com/products/els60-0087-12v-solenoid?srsltid=AfmBOoqjkDQTjLNIK81Dm0m_fLnYAsLEz2zK8cGSZdZXpFsj3s9lTvJz (https://www.reliableaftermarketparts.com/products/els60-0087-12v-solenoid?srsltid=AfmBOoqjkDQTjLNIK81Dm0m_fLnYAsLEz2zK8cGSZdZXpFsj3s9lTvJz)
I got the tractor going today but it was bothering my why the first solenoid didnt work so I sat down and sketched up a circuit to see if it would support my theory that it was intended for a positive ground system.
I think my theory was correct because I was able to come up with a circuit that would work.
'Yestereday's Tractors' store might be worth a look.
FPP, I'm the same way, I have to know why something works or doesn't work. Just getting it fixed isn't good enough. I could never stand to just be a parts changer. Your diagram makes sense to me although I have never worked on anything that had a positive ground although I once worked on a rock truck where a fellow charged a set of dead batteries with his welder and the leads were reversed. Just about drove me nuts and cost a lot of money to repair.
I once was working on three-way switches. bought a new one and the circuit still did not work. I bought a bad 3 way. they must have had a bad run cause I have got 3 bad ones from the store over the years. I now know all about 3- and 4-way switches and circuits.
The only reason I was aware of positive ground being a thing was because I worked on an old Ford 8N that was a 6v system. The positive terminal of the battery was wired to the frame at which point I go What????
old VWs were positive ground too.
Was laying in bed this morning and for some reason realized that the circuit I showed yesterday was wrong.
This one is correct.
(actually I was testing you guys ffcheesy ffcheesy )
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Wlmedley, trying to troubleshooting something that someone has had their filthy hands on first is the worst. I'm working through some issues on a Detroit 4-53 right now, trying to figure out mistakes made by hands that didn't belong there. It's not fun at all.