MF 135 Electrical Problem - need suggestions

[Dark Ridge]

Our MF 135 has started draining the battery while sitting in the barn. We initially thought the battery had gone bad, so we purchased a new one and it to drained over night. I read on this website, on another post, that this could be caused by a bad oil pressure switch. I checked the voltage with a meter while the tractor was off and read voltage on both sides of the switch, leading me to assume the switch had stuck in a closed position thus draining the battery. When running, the alternator produced approximately 14V. I purchased a new oil pressure switch and new voltage regulator.

Here is my problem. After installing the new switch and regulator, the alternator is no longer providing power (.45V). I know that the oil pressure switch and regulator must "excite" the alternator, but I cannot figure out what the problem is. I took the alternator to a alternator service and it check out okay. Thinking one of the new parts might be bad, I put the old regulator back on, same problem. I then put the old oil pressure switch on, and again the same problem. So I have both old parts back on and still not getting power from alternator. Any help is appreciated.

 

[Soundguy]

is it really an alternator or is it a generator. if a generator, it will need to be polarized.

if an alternator, post the type it is.

if you are unsure of either question, post a pif lengthwise and from the back showing the wire connections.

soundguy

 

[Dark Ridge]

Thanks for asking. It is a alternator. I would have to look to see the make/model. Some update. After my post, we rechecked the wiring and re-installed the new oil pressure switch and voltage regulator. The alternator guy had given Dad a diagram of how it should be connected to the regulator F, 2, 3, 4. He had said that wire 3 should have power on it all the time coming from the battery. So, we charged the battery to 12.34V and re-installed it. We then clutch started it and the alternator started charging. Everything seems to be working fine as of now. I am assuming that the voltage regulator needed power from the battery in order to have the alternator "kick in". Does this sound reasonable? We let the tractor run awhile to help recharge the battery and are planning to recheck the voltage in the morning. If there is no voltage drop, then I assume the oil pressure switch was bad and the new one corrected the problem. If battery is dead in the a.m., then I'll be back on here looking for more information. Have a good evening and again, thanks.

 

[flusher]

Our MF 135 has started draining the battery while sitting in the barn. We initially thought the battery had gone bad, so we purchased a new one and it to drained over night. I read on this website, on another post, that this could be caused by a bad oil pressure switch. I checked the voltage with a meter while the tractor was off and read voltage on both sides of the switch, leading me to assume the switch had stuck in a closed position thus draining the battery. When running, the alternator produced approximately 14V. I purchased a new oil pressure switch and new voltage regulator.

Here is my problem. After installing the new switch and regulator, the alternator is no longer providing power (.45V). I know that the oil pressure switch and regulator must "excite" the alternator, but I cannot figure out what the problem is. I took the alternator to a alternator service and it check out okay. Thinking one of the new parts might be bad, I put the old regulator back on, same problem. I then put the old oil pressure switch on, and again the same problem. So I have both old parts back on and still not getting power from alternator. Any help is appreciated.

It's been a while since I rewired my 1964 MF135 diesel. Could also be a short in the fuel gauge sensor circuit. I'd disconnect the sensor and see if the problem is fixed.

 

[Soundguy]

I'm not a MF person, but I've never heard of an oil sender exciting an alternator. I think you'll be back in the morning.

Actually.. that's not a weird one. I've seen applications like that before.

soundguy

 

[Soundguy]

Thanks for asking. It is a alternator. I would have to look to see the make/model. Some update. After my post, we rechecked the wiring and re-installed the new oil pressure switch and voltage regulator. The alternator guy had given Dad a diagram of how it should be connected to the regulator F, 2, 3, 4. He had said that wire 3 should have power on it all the time coming from the battery. So, we charged the battery to 12.34V and re-installed it. We then clutch started it and the alternator started charging. Everything seems to be working fine as of now. I am assuming that the voltage regulator needed power from the battery in order to have the alternator "kick in". Does this sound reasonable? We let the tractor run awhile to help recharge the battery and are planning to recheck the voltage in the morning. If there is no voltage drop, then I assume the oil pressure switch was bad and the new one corrected the problem. If battery is dead in the a.m., then I'll be back on here looking for more information. Have a good evening and again, thanks.

yep.. some designs use an excite line. for instance.. a delco 10/12 SI use blade terminal #1 as an excite line, when used in a 3 wire setup.

post back and let us know.

soundguy

 

[Dark Ridge]

After changing the oil pressure switch, voltage regulator, having the alternator checked by a alternator rebuild shop, and charging the battery to 13 or so volts the problem is now fixed. I feel sure it was the pressure switch. With the old pressure switch I was getting power on both sides of the switch with the ignition off. With the new pressure switch, I only have power on one side until the engine is cranked and oil pressure builds. As someone else posted, our 135 uses the oil pressure switch to "excite" the alternator, as was confirmed by the alternator shop. Thanks for everyone's comments and suggestions. I'm sure I'll have more "problems" in the future.

 

[Soundguy]

that's a good old machine.. if I didn't collect fords.. MF's would be right up there on my list.

soundguy