Testing 12V Generator Output, 58 CJ5?

My generator on a F134 seems to be just barely charging. The wiring has been changed to 12v. With nothing but the elec. fuel pump running the battery condition gauge shows just under normal. When I turn the heater on the gauge drops to 10v. Would this cause the battery to be undercharging.
Question is do I need some special type of tester to check it or is this normal ?

Thanks for any info !

 

It may be the Voltage regulator or if the battery has been disconnected you may need to polarize the generator which is a simple procedure of jumping two terminals on the regulator momentarily. It's been a few years since I've had a truck with a generator in it but I'm sure some one will come along shortly with that information.

 

use a volt meter to confirm, a guage is super iffy on accuracy.

 

To polarize the genny momentarily jump the battery terminal to the field terminal. Once polarized if all else is good your generator will produce 12- 14 volts above idle.

 

Try with a fully charged battery, be sure your battery is not the issue. Make sure battery connections are good at both ends.
Voltage drop should be minimal, even without the generator input.

FSM has test procedures for generators and voltage regulators.

 

Thanks to all ! When I first bought the Jeep it had an old " for sale" battery in it. I put a new one in, it ran OK for a while but drained, running off the battery I guess. I tried the polarize thing but not sure I got it right but it hasn't drained the battery so far.

Glenn, it occurs at all RPM.

 

Belt and tension OK.

 

Thanks Karl, would that be the + battery terminal to the field terminal on the genny ? How long to jump ? Should the engine be running ?
Thanks for your help !

 

Only a momentary flash, engine off.
Proper connections depend on which make of generator/regulator you have. ('A' or 'B' type.)

According to Walt, Prestolite you should flash the 'Field." Delco you should flash "Armature."

 

Thanks to all ,with all the help and info provided I think I've found the solution.
John,,,,,

 

Glad to hear that, Enjoy your Jeep!

 

Thanks Glenn, I finally got a meter, best I can tell the genny may not be working up to par, I've read that if the 12v redo and the v regulator isn't matched it might be the problem, it looks to be an old one, 1958 WILLYS, has the instruction to polarize the generator on it.

Sorry for all the questions, when it comes to automotive elec. I'm lost.

I'll try to figure out how to test the regulator but it seems the batt isn't charging. When I start the engine the volt gauge shows a drop, I think because of the elec. fuel pump. If I turn on the heater the gauge drops down quite a bit, to 10v. After running the engine with only the fuel pump running the battery all to soon needs recharging, it's a new batt. Ignition running only off batt . ?

Thanks for any ideas. I really appreciate the help from all the members !

 

Bring it up to Taos, I'll give you a hand. If you can't do that make sure all your grounds are clean and tight on bare metal. Check all conections and don't trust crimp connectors even if they appear to be good. Properly soldered connections are your friend. I'm not one to just throw parts at a problem but a regulator is cheap and will eliminate that aspect of it one way or the other. Be sure to polarize it. Do you have a wiring schematic? It would be worth having one and tracing all the wires in the charging circuit down to make sure they are correct. Previous owners can make real messes of wiring on a vehicle. Be systematic in your trouble shooting and trace each circuit back to its source one at a time, don't jump place to place, be methodical. Some years back there were good books on automotive wiring that covered the sort of technology our vehicles use, see if you can find a copy.

If all this turns up short in the charging dept. process of elimination will be leaning in the direction of the generator itself. If you have an old timer in your area that works on them have him thoroughly test it for you.

 

x2.

And don't go nuts with replacing stuff (yet). It could be as simple as a stuck/worn brush, dirty commutator, or a loose wire.