Charging System quandry

[Chris53]

This is for any of the electrical system experts here: The ammeter on my Cub goes negative when the switch is turned on (correct) and does not move after the engine is running (it remains negative). Going through the troubleshooting flow chart that's floating around this site yields no response to any of the tests, which points to a bad generator. Well, okay, except for this: my voltmeter reads 7.5 - 8.0 volts at the battery with the engine running, and that's proper charging voltage for a 6-volt system. That tells me all (including the generator) is good. What am I missing?

This issue is also present on my '53 Super H. Nuts...

[Don McCombs]

Have you polarized your generator(s)?

viewtopic.php?f=140&t=56748

[Chris53]

Yes, that's one of the first things to do on the checklist, although I noticed no sparks when doing so. Would an un-polarized generator produce proper voltage at the battery?

[bofahs]

OK, your battery is being charged. 7.5 - 8 v. is great. I suspect your ammeter is wired backwards. Remember, for a Positive Ground System, the only wire on the negative (-) terminal of the ammeter goes to the starter. Might be counterintuitive, but, there it is.

[Chris53]

I considered that it was wired backwards, but why would it show negative with the ignition turned on, engine not running?

[bofahs]

Hmmm.. I had that happen with my 12 v. system - turns out I was using an ammeter from the auto parts store with a much greater range, and far less sensitivity than the Cub + and - ammeter. If yours is like the original, I'm stumped!

[Chris53]

If the ammeter was the incorrect range it would just move less (or more) than it would otherwise, but it would still behave normally (discharge with electrics on, charge with engine running). Mine moves to the left and stays there regardless. I'm not really worried since the charging voltage is good, but I sure would like to understand what's going on and maybe fix it. Plus both my Farmalls do this.

[Glen]

Hi,
You could try a new ammeter, I can't tell if it will work better, but you could try one.

TM Tractor has new ammeters that look about like the originals.
Here is what they say at their website.

Special production ammeters
Made in the USA at the request of TM Tractor Parts

If your Cub is a 1953, it probably looks like this one.

http://www.tmtractor.com/new/el/202fp.htm

[Eugene]

Faulty amp gauge.

[Jim Becker]

Where does your ammeter needle point when everything is off? It may not be on the zero mark of the face. Anything to the right of where it is pointing is charging.

[Chris53]

Interesting question. The needle is pretty much centered when everything is off. It moves noticeably to the left of that position when on and stays there.

I borrowed an ammeter from a friend's Farmall C and it showed the same behavior. Yes, it could be bad as well (his tractor is not currently running, a work in progress) but it persuaded me that buying a new one was not necessarily warranted (yet). It does look like the one at the TM Tractor link.

[birddog]

Is it possible that there is a different wire coming from the regulator that's actually charging the battery without going through the AMP gauge? The Amp gauge being hooked to the ignition but not having amperage from the regulator just keeps reading the ignition draw. The AMP gauge only reads amperage so it wouldn't detect the change in voltage at the battery.

[Chris53]

Well, that's going to take some digging but it's worth tracing the wiring. I have the wiring diagram in the Service Manual and it shouldn't take too long on a rainy day. There are four wires leading from the regulator and I'll make sure each goes to the right destination. If that's the case it would seem both my tractors have the same issue...weird.

[tst]

this might help

[ntrenn]

6 v system with 8 v at battery should not show a charge.

do you have a regulator? If so pull the cover and check to see if the contacts are cycling. Mine stick on a regular basis but they usually start working after a while....you can manually cycle the cutout to make it charge i just dont remember which is which..