Generator relay charging system: How to troubleshoot?

Wed Nov 09, 2005 6:34 pm

All, this is on a Super A rather than a Cub, but I posted it anyway because I figure what I need to know would apply to a Cub too. Anyway, you have to understand that I don't do electricity well. I can wire up a single pole switch or a recepticle, but as far as where the current comes from, where it goes, and WHY, I am clueless. It works by magic as far as I'm concerned. (Near as I can tell, that's also how carbs and magnetos work :wink: ) Anway I am getting ready to re-wire my Super A that has been painted. Everything is new except for the 4-position light switch. I have cleaned it and it seems to be in good working order.

My FIL is pretty good with electronics and so forth, and has a voltmeter and other electrical test equipment. What I want to know is, once I have everything hooked up, what should the voltage, etc. read at various points in the system? In other words, what should I touch with the voltmeter, and when I do what should it read to verify everything is working?

The 'ol Super A has never wanted to charge just right in the last 20 or so years. I am sure it was just poor connections, poor grounds, and age. But it has given so much trouble in the past, I want to make sure I can troubleshoot it from A-Z before I start connecting things......


Wed Nov 16, 2005 8:40 am

Bringing this back to the front....does anyone know how??


Wed Nov 16, 2005 9:23 am

Super A - first of all, since you are re-wiring with a 4 position switch I assume you are using a cut-out in the system. When you wire, make sure the connections are clean and tight. Also make sure all electrical components have a good clean ground connection. Once all components are mounted and wired, polarize the generator. This is done by momentarily placing a jumper wire from the battery terminal to the generator terminal on the cut-out.
Now, before starting the tractor, measure the voltage across the battery terminals. This usually runs from 6.0 to 6.6 volts. Start the tractor and at about half throttle, re-measure the voltage across the battery. If the system is charging, you should have a positive deflection on the tractor ammeter and you should read about 7 to 7.4 volts at the battery. I can't emphasize enough how important the grounds are.

If the system is not charging, follow the troubleshooting chart here:

Wed Nov 16, 2005 11:32 am


You can use this picture to double check your wiring... sometimes a picture is better than a diagram. This stuff happens to be from an H, but all IH tractors use the same electricity. :D

I think John (Red) Fritz made the picture originally.