Farmall Cub

Good afternoon. I am still chasing down gremlins on my 656 gas charging system ( serial number 35500.) and have a few quick questions if someone might be able to answer for me. I just replaced the front wiring harness as it looked pretty dicey anyways. During the replacement, I noticed that the wire from the voltage regulator ground to the alternator ground was not connected. The connector at the alternator was not connected and was taped up. Could this be a problem? I have course connected it with the ground in place according to the new wiring harness. Also, the amp tell light bulb seems to be burned out. I am replacing it. Based on my very rudimentary knowledge, that light bulb circuit serves to energize the alternator. Am I right about this? If so, my dad explain why the relatively new alternator was not putting out voltage to the battery?

This tractor is really hard to start when it’s cold, and I have to plug in the block heater for several hours, even when the temperature is in the teens. I am replacing the plugs, points, plug, wires, and condenser. Any other things that you can think of that I should consider to help this start better in the cold weather? The coil looks to be original. Should I think about replacing that as well? My comparison for cold-weather starting is my Farmall 184, which will fire up in any temperature without any help.


Thanks for your help here. I am really trying to keep this old girl running.

PS. One more question – what do you recommend gapping auto light 386 spark plugs to

The tune up should help the cold starting issue. We used a shot or two of starting fluid when it was -10F or colder.

The (edit) light bulb energizes the alternator and also prevents the alternator from discharging the battery when engine is off.

Ground wire, not sure, where does it attach to the alternator? The Delco alternator grounds itself to it's mounting bracket.

Gap spark plugs to the tractor's specification. Not looking it up, my guess, .032' or .036".

A poster on Yesterday's Tractors says this...

Points .020 plugs .025 to .030.

Thanks for the feedback – sorry it took so long to get back. I have solved the charging issue. It was a bad voltage regulator. And boy was that a pain in the replace. It was tucked up in a corner under the gas tank. Now, my last problem to solve is how to get the spark plugs out. The recess where the plug sits is too narrow to get a plug socket or a deep well socket in there. I’m gonna have to think on this one…

How about a thin wall socket for the sparkplugs?

Don McCombs wrote:How about a thin wall socket for the sparkplugs?

I honestly didn’t know there was such a thing! I’m not much of a mechanic . I will have to see if I can find one. Thanks!

I am now officially at my wits end. Ask for the spark plugs, I made my own thin wall socket, and that all went fine. The plugs looked horrible. I put new auto light 386 plugs in with the .025 gap. Starts and runs great. But I am back to the charging issue. Once I replace the voltage regulator last night, it was charging with 13.6 V at the battery at idle. I put it all back together today and start it up and the amp light would not go out. Voltage at the battery Was 12.4 and did not change with RPMs. The alternator is fairly new but I went ahead and replaced it anyways. No luck. So to this point I have replace the alternator, wiring, harness, voltage, regulator, all without solving the problem. What am I missing? it is a 10 DN alternator from Steiner. I have no idea what to do next. Any suggestions would be very much appreciate it. Thanks!

Bad connection, probably a ground.

Is it hard starting or hard cranking? If it is hard cranking when it is cold then it might be the power steering causing pressure that the starter has to overcome. Does it have a destroking option? My JD 3020 was a beast to start before I put in the destroke screw.

I am more familiar with the 10si than the 10dn, but from what I have read about the 10dn it requires a drive signal, typically through the panel light to signal the alternator to start charging, or on a tractor without a panel light through a diode to a 12volt source. The symptoms that you list sound like a intermittent problem with the 12 volts that needs to get to the drive pin on the alternator, I think to the #1 pin on the connector. Once the alternator sees that 12 volts it should start charging and then the regulator comes into play to manage the output. And once the alternator starts charging it asserts a 12 volt signal on the drive line which causes the panel light to go out. So if the wiring is good and the panel light it not going out I think that points at an alternator problem (and not the regulator), but I would check for a wiring problem to #1 pin, such as a loose connector in the plug.

I don't have access to a 656 wiring diagram, but check my info against a wiring diagram in your owners manual. If the panel light has 12v on one side of it and the other side goes to pin #1 on the alternator, then you can test to see if the alternator will start charging by connecting a wire to 12 volts and momentarily touching the other end of the wire to pin #1 while the tractor is running, the panel light is on and the alternator is not charging. If alternator starts charging your problem is between the alternator and the panel light. If alternator does not start charging then you have an alternator issue.

At least those are my thoughts and I beg forgiveness if I misstated anything.

Thanks for the ideas. I do wonder if it is an alternator energizing issue. I will try jumping from 12 V to the F terminal and see if that gets it running.

I found that my service manual for the 560 has a chapter on testing the alternator with the external regulator with a circuit diagram. My comments about the voltage regulator above are misleading. But the first check suggested is to test for full output without the regulator connected. Remove the R & F plug and put a jumper wire from battery + to F terminal. With engine at high idle should have full output on an amp meter B+ to battery. If less than full output check belt, if still less then suspect alternator. If no output, with engine stopped check voltage at B+ on alternator. If no voltage check wiring. If voltage service alternator.

I need to leave but can look at more tests later.

Thanks, Phil. I will test the output with the regular disconnected and report back. I am also thinking… The new regulator I put on, that I got from Steiner, looked different from the one that I took off and the one that Brillman shows. On the backside of the new regulator there are two coils that look sort of like resistors. These are not present on the old regulator. What’s weird is that it worked briefly the night that I switched the regulator. I got 13.6 V at the battery at idle. And now nothing. Could I have fried the new regulator? Was that somehow the wrong regulator? For 14 bucks and a whole lot of work, maybe I should swap out regulators again. Is a big pain in the butt where the regulator is located…

By the way, Phil, I am just up the road from you a bit. If you are in Grand Rapids, I am in the UP.

Update: I jumped from the F terminal on the alternator to the back terminal and got a voltage rise - it went over 15 before i disconnected it. So that tells me that the alternator is working. I assume that the voltage went so high because the voltage regulator was not in the circuit and it was putting out max voltage. Right? So I wonder if there is a problem with the new voltage regulator. The voltage regulator that Brillman has looks just like the one I took off originally so I guess I will pick up one of those and give it a try. If that doesn’t work, I am back to square one