Ok so I am going to try and be as concise as possible with explaining my situation... So i recently bought a 1955 1/2 gmc 100 pickup and I initially did a general tuneup one it, plugs, oil, hoses and everything seemed to run fine I then replaced the ignition coil, plug wires, and had the generator rebuilt, now it runs great however instead of getting a charge on my amp meter, i get a discharge, a little at idle and higher the more revs i give the engine, now when testing with a voltmeter on the battery it reads 12.5ish, slowly goes up at idle sometimes quicker sometimes slower goes up to about 13.4 then sorta stays there and then if i rev it comes down to around 11.9 and goes back over again...all that seems fine so just to make sure i replaced the regulator, and charges even faster, but still again reads discharge Now the truck os negative ground so...could it be plausable that at one point it was switched to neg ground but was originally pos ground and the amp meter was never changed? I find this to be hard to believe considering i swear it worked when i bought it, but then again the generator was bad so maybe it was discharging and now its charging? Not sure? Any thoughts or help would be greatly appreciated
Generators need to be flashed before using to orient the direction of the field coils. Test the amp gauge wire with an inductive amp gauge. It has been a few years since I worked on a generator system so I don't remember the proper way to flash and there are two types of generators so find the info in an old manual or on line. Jim (55willys)
Turn the key to the on position then turn on the head lights see which way the amp meter moves, it should show discharge, if it shows charge then reverse the amp meter wires. Posted using the Full Custom H.A.M.B. App!
I thought about that after posting, so i went outside and tried that, key on but engine off and turn lights on it goes slightly into charge...so its safe to assume it is the gauge Also i had the same generator rebuilt, so my guess is its the same way it was before i had it built, they wouldnt flash it the other way would they?
Why did you have the generator rebuilt in the first place and have you checked or replaced the voltage regulator?
The kind of "servicing" that requires you to polarize a generator is if you are replacing the armature assembly (or replacing the commutator on the existing armature) or if you are replacing the field coil(s) assembly. If all they did was disassemble, clean, lubricate and re-assemble, they did nothing that would alter the residual magnetism of the generator or de-magnetize any of the components. That being said it is very possible that incorrect polarization is you problem
I had the generator rebuilt because it wasnt charging at all, no voltage coming off it at all, had it rebuilt now the correct voltage does come off of it
If the rebuilder thought that the truck was still positive ground and checked it that way that might be the case but we always ask polarity and that avoids any problems. Posted using the Full Custom H.A.M.B. App!
The voltage shouldn't go down when increasing the engine speed. If the voltage is dropping below the battery voltage, the system is discharging so the meter is reading correctly. Is the belt tight on the generator? One way to check is to try to turn the generator with the engine shut off. As had been posted, you need to polarize the generator any time you remove either the generator or regulator. A circuit generators (most GM models) strike the battery and armature posts on the generator together using a jumper wire or a pair of pliers, (spread the handles) and touch the two posts together briefly. You should see a small spark then you are done. You need to do this every time you remove either the generator or regulator for service.
Well the voltage doesn't really go down, just slightly but i would say it doesn't go down, any fluctuation i would say is belt slippage but i have since tightened it...i know the did jump it like that when they started the rebuild, should i assume i need to do that before reinstalling it, i dont think so? Also it should be noted that the engine runs once started without the battery
If they bench checked the generator negative ground after the rebuild you should be OK. Posted using the Full Custom H.A.M.B. App!
You should always polarize a rebuilt just in case. They can even lose their charge if the car or generator sits around for months or years. But in this case it sounds like it is OK.
Was the regulator installed at the same time as the generator or was it replaced after it was already polarized?
I'm betting you didn't notice that this is a 12 year old thread...and the OP has not been seen for 5 years.
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