Farmall 400 12v Electrical Problems

Absent Minded Farmer · Jun 21, 2009

Well, this is a new one on me. With the engine off & the headlights on, the ammeter reads that it is charging. I do know the tractor charges nothing, so far, running or otherwise. Battery is ok. I can charge it overnight & get a good many starts from it after that. It's running a pretty new alt & the previous owner changed out the points. Inside what I thought was the box for the new points was another brand new points set (a sign maybe?). It has an odd buzz comming from the distributor as well. The engine cuts out, at 3/4+ throttle, every once & a while. Shuts down - dead. Crank & crank & crank & then it put-puts to life like a hit-n-miss. It could act up a half hour later; it could act up a few days later. No set pattern. Any ideas? Thanks - Mike

Sorry about the pic, btw, had to use my phone.

Thresherman · Jun 21, 2009

My guess is the previous owner did not cahnge the wires on the ammeter. I think the 400 originally was 6V POS ground. That would make the meter operate backwards if switched to NEG ground. Probally could use a ballast resister in the dist line also. If you search this site you will find wiring diagrams from BOB M. You might want to check them, an M or super M should be about the same.

IH2444 · Jun 21, 2009

First problem. Ammeter wired backwards?

Second problem ignition switch is not cutting off power to the coil/points sounds like.
With ignition off check voltage on + side of coil. should be about 6 v with points closed and 12V with points open.

IH2444 · Jun 21, 2009

yes on thresherman about the ballast resistor. If you read 12V on the + side of the coil with the points closed then you either need a ballast resistor or a coil with internal resistor. Napa has em for about $18. And the easiest fix for that.

RobMD · Jun 21, 2009

First of all, your ammeter is wired backwards. REVERSE the leads.

Secondly, if the alternator is fairly new, obviously, someone didn't wire it up right. If you have a ONE WIRE ALTERNATOR - the single lead goes to the SOURCE SIDE OF THE AMMETER.

Is the tractor wired for positive or negative ground? With the alternator, people usually run these negative ground. THUS, the coil wires should be REVERSED.

Lastly, an engine that kills itself for no apparent reason after running fine for a while indicates a condenser problem. Replace condenser. (Either that - OR you have a FUEL PROBLEM, which would be that the carb is running out of gas at higher rpms - to fix, clean tank, replace sediment bowl strainer, and make sure carb has a steady flow of fuel)

RobMD · Jun 21, 2009

Has the coil been changed to a TRUE 12V COIL?

Absent Minded Farmer · Jun 21, 2009

is this the resistor? As for the ground, it's neg. I think it's getting plenty of fuel. The tractor smokes quite a bit when it comes back to life. I'll change the condenser first. I think it's a 12v coil. It's identical to the one on my 12v W6. I guess this don't sound as serious as I thought. I think I'll start putzing with it tonight, yet. Thanks Guys! - Mike

John B. · Jun 22, 2009

It sounds like to me that your electrical system has been changed from Positive ground to Negative ground. IF so you will have to reverse the leads on the amp meter as well as on the coil. This would explain the engine cutting out at 3/4 throttle.

Farmall 400 12v Electrical Problems

Absent Minded Farmer

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Thresherman

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IH2444

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IH2444

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RobMD

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RobMD

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Absent Minded Farmer

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John B.

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