I picked up a 49 farmall H last week that was converted to 12v with 12v generator. It worked and started fine all week. Monday I gave it an oil change, and then Tuesday it had a dead battery. I fired it up after a jump and it ran fine for 30 minutes. I've checked the voltage at the battery while running and i'm getting 11.2 volts. I've tried to check the generator but i've been getting numbers that don't seem to make any sense. Like connecting the AMP and Field posts and only getting .22 volts, when I believe I should be getting 15-40 volts. I've looked into wiring diagrams to try and make sense of the regulator, but it doesn't match the one on the tractor at all, and i'm really not great with electronics.
I've attached a photo of the genny and regulator. Any tips on diagnosis?
Here is a link to the electrical section of the 1955 Pontiac factory shop manual: http://www.pontiacsafari.com/55/ShopManual/12%20-%20Electrical%20and%20Instruments.pdf Yes, it's not a Farmall manual, but the general configuration of the generator and charging system will be pretty much the same. Try momentarily grounding the F terminal to see if it starts charging.
In my experience, the main thing that goes wrong with generators is worn out brushes. It doesn't look like yours has been serviced in a long time so taking it apart and cleaning it up may not be a bad idea anyway, and then you can tell if the brushes are okay. It would be a good time to check the bearings and replace them if necessary too.
Check for bad connections or broken wires. A tractor is susceptible to mice or other critters chewing on things.
The voltage regulator could be at fault. Its contacts may be dirty and need cleaning with a points file. You can try manually pushing in on the contacts while monitoring voltage to see if it starts charging.
In reply to stuart in mn :
I agree with you. I was working on a 57 TR3 that was not charging. Disassembled and found the brush holders were corroded and not allowing brushes to contact the commutator. I also found out that a generator should operate like a motor if the brushes are making contact.
I honestly don't know much that's specific to old DC generators but given what that looks like and what little i know, it looks like it isn't regulated at all (unless there is more stuff going on under that relay that i cant see) and just gets a switched power to field from the ignition switch and has a relay on top that engages when the generator is making voltage above battery voltage and hooks it to the battery. So you should be able to check switched power to the field. Resistance to ground from where the field goes in (which will go through brush, commutator, armature winding, back through commutator and other brush and then to ground). The relay coil winding which should have some resistance to ground and not be near zero or in the hundreds. Resistance across the contact points of the relay when engaged (can probably just push it closed with fingers for testing). And resistance or voltage drop of the actual charge wire going from the relay to battery. And least likely, resistance to ground of the housing, but if that had high resistance you probably wouldn't have good cranking speed either so it's unlikely.
Alternators will often bolt in where a generator was, and they don't require an ancient bearded wizard to...do that thing...polarize! That's it.
Thanks for the ideas guys.
This is a dumb question, but it looks like the top post would be the + post and the bottom the field post right?
Should be marked, we had an H on the farm but don't remember having problems with the charging system. That band that wraps around the rear of the housing will give you visual access to the brushes and commutator.
Once you've tested what's been said above, you can test a spinning generator as follows:
- Disconnect the terminal that goes to the regulator.
- With the generator spinning, the other terminal should show about 3 volts at idle and go up slightly with RPM
- Next, temporality short the terminal that goes to the regulator to the other terminal. The voltage should quickly go to 20 volts or more.
- If it does these things properly, the generator is fine and you need to look for a new regulator or other wiring issues
(I'm assuming this is a generator with 2 terminals like most cars)
Most generator problems were usually brushes and/or a dirty commutator.
One of the things that generators do poorly is charge at idle. Run that sucker at 2300 rpm with a volt meter on the battery to see what it is doing.
I haven't had much time to mess with it, but I pulled it and checked it with a battery and it spun just fine. So i think the brushes are okay. Hopefully i'll be able to get some voltages tomorrow.
My Dad and I never mastered the generator on our '52 Farmall C or Farmall Cub. However, we had a convenient hill to park them on, and they didn't use very much electrical power. They also started pretty well with their hand cranks. Do you have one? I think I have an extra, if the H uses the same as a C.
