Deuce voltage drop

[dschuler]

Hi everyone, I'm having some issues with the voltage in my deuce. It's a '66 Kaiser with the Hercules multifuel engine. It came with a generator, which is where my problem started. One night the truck just died, and found the batteries completely drained. Replaced the generator for a civilian 24v alternator, which i bought from Tim at Wolverine Technologies. The alternator started charging at idle, but after a few hours running, it did the same thing. So, new alternator, new ground straps, cleaned every ground connection I could find in the truck, put new batteries and cleaned battery leads. Started the truck, hooked my volt meter and started charging, slowly but charging. But as soon as I turned my lights on, sure enough it started to drop voltage like a hot potato and when I would accelerate, it would drop voltage even faster!!! I dying over here trying to figure out this thing and I don't know what else I can do or what could be causing the problem. Any advice will be greatly appreciated

 

[M543A2]

It reads like you had the first alternator quit and got another. Did Wolverine test the failed one to hopefully give you an idea what caused it? You might have a ground you have not found or is missing. Did the alternator get overly hot like it was working hard to charge?
Do the batteries run down while the truck is sitting, engine off? If they do, you might have a current drain somewhere. You might try removing the ground cable at the batteries and check for a current drain from the battery post to the cable. Sometimes you will also see this demonstrated by a spark when you touch the cable clamp to the battery post, switches all in the off position.
Does the problem show up only when using your lights? We had one truck with a wire that had gotten pinched between a clamp and the body, shorting out. Are your headlight wire grounds on the radiator mount good or broken? Bad light switch? You can try the same experiment as above with the battery cable removed, light switch on, other switches off, and see if you have a really high current draw.
As you can see and know already, there are many things to check. You have done very well, but some small thing is still missing. Sorry you are having such a frustrating time!

 

[theeDIZ]

When I picked up my deuce the alt was fried , I picked up a newly rebuilt one but traced all the wires in the front harness before installing it. Found a few bad spots in wiring that i repaired as to not burn up the new alt. Hope this helps

 

[dschuler]

Well, the problem only happens when the truck is running. The batteries hold when the truck is off and the accessories switch is also off, so no current drain on that part. I don't know if the generator got hot or not, I did not check that and already disposed it. I still have to trace the wires back, but with it being a 50 yo truck, I would assume that some of them are corroded. What intrigues me is the fact that as the RPM rise, the voltage drops. Shouldn't it be the opposite?? I unplugged the headlights and it stopped draining the batteries that fast, but as I drive (since the truck is accelerating) the voltage continues to drop. Could a short wire cause that? Am I missing something here??

 

[The HUlk]

Could a short wire cause that? Am I missing something here??

I would have to say yes in a certain circumstance. A hypothetical example... Let's say some wire insulation has deteriorated to the point where when there is no movement there is a high resistance shorted connection. In this state a low discharge may occur. And let's say that when the vehicle is vibrating the movement causes the resistance to decrease to a level where much more heat is created from a loss of energy(voltage) but not so much as to cause the wire to burn or worse. I have seen old wiring cause intermitent problems like this. Perhaps a harness replacement is in order?

 

[rustystud]

You have a generator correct ? That means you have an external voltage regulator. Did you ever test it ? That is what usually goes bad, the regulator not the generator.

I forgot to add that when you replace the regulator you must polarize it. The TM will tell you how this is done. Usually you ground the regulator momentarily. It just depends which wire to do this to.

 

[dschuler]

I replaced the generator for a civilian 24v alternator

 

[The HUlk]

An unusually high need for charging of the batteries will cause failure of components in the charging system.

 

[rustystud]

I replaced the generator for a civilian 24v alternator

I didn't see that part, my bad. You replaced the batteries and the grounds. Did you ever check the positive cable ? The ends can get corroded and you will not even see it. To test you must twist the crimped end on the cable. If you feel any give then the crimp has come loose, most likely due to corrosion on the cable. Either replace the cable or try and salvage the old cable by cutting out the corroded section and installing a new cable end. Sounds like your alternators are trying to push to much current (extremely high resistance) . So check all the cables not just the grounds.