Farmall 400 Overcharge

I just finished converted my 400 to 12V with an alternator. Starts and runs good but the Amp gauge pegs out on the charging side as soon as the tractor starts and it never moves until I turn it off. Lights are not hooked up and everything else but the battery and gauge are new. Am thinking I might just have it wired wrong to my switch. What do I need to check??? Thanks!

Could be a bad gauge. Your battery will boil acid out if overcharging. Keep a close watch on it and if it don't loose acid get another ammeter. I prefer a voltmeter myself. David.............

I know the battery is weak. How long would the tractor need to run before the battery boils? I havent run it very long because I didnt want to burn something up. I have a couple working gauges I took off of tractors I restored for show so I will check that out in the morning.

Whip out an analog voltmeter and measure the charging voltage at the battery and see what is REALLY going on.
Anything over 14.8 or so IS too much.

I just went through this last week with my super m. I rewired mine a year ago, everything was fine until a few days ago, and I developed an overcharge. Is the alternator a delco 10 si? Either way, check the voltage at the battery with an analog multitester, when its running. A digital meter bounces all over the place anytime you get near a running tractor thats this old. If its over 15 its too high, mine was 15.5. With a charged battery I think you should be around 14.2 volts on the battery posts.

Make sure the number 2 terminal on the alternator has good contact with either the "bat" post on the back of the alternator, or directly to the battery. The #2 terminal on the alternator senses the batterys voltage and tells the alternator to reduce its output. A bad connection/plug can create an overcharge. Run a jumper from the sense post #2 alternator terminal directly to the battery to eliminate the possibility of a bad connection at the alternator plug.

Your battery may be bad too, and that will cause it to boil over. Have it load tested, or swap it out with another one. It will cook itself quick, so don"t run it long.

Your ammeter should jump to the positive side right after startup, and within a minute or two settle back down to 0 or just above. My amp guage was bad, and it was pegging itself too. A new one cured it. There was a big difference in needle "play" or movement from the old one as compared to the new one. I could shake the old one (when it was off the tractor) and get the needle to move all over the place, but with the new one the needle stays dead on zero when I shook it. Mainly, just get a handheld tester and take a reading on the battery, otherwise you"ll be nickel and diming yourself. Also where did you get the alternator. Ive seen brand new ones fail.

I had a battery blow up on my brothers WD45. It was like a 12 ga. shotgun went off next to my head. You don't want to have your battery blow up between your legs either. Do not run it until you check the fluid level in the battery. This one had gone dry and that saved me from getting burned, but that is why it blew up.
Steve

The info below should do the trick (good stuff) The new gauge should read (numbers on gauge front) to a bit more than the alternator output to be sure it is not getting over heated by the output of the alt. The output is usually stamped on the alt frame. 14.2 to 14.6 is considered normal into a fully charged good battery. With a weak battery the system will not do well, nor be accurately analyzed. JimN

Mark, While you are absorbing all the excellant suggestions, disconnect both cables from your battery, check the fluid levels and put it on a charger to see if it will fully charge normally.
Clean all the terminals and connectors while it is charging.
Then do the checks suggested.
Dell