Help Needed - Car Wont Charge

I have a charging issue that I cant figure out.

I am finishing up the V8 swap in my 51 Chevy. The alternator I have is from an 88 Suburban and was originally a serpentine setup, that I changed to V belts. It has a main lug and a square connector with 2 wires coming out of it. The wires are lettered L and F.

After talking to some buddies I have it wired the following way:

Main lug goes to the amp gauge, then to the battery.
L wire goes to the ignition switch, thru a diode.
F is not hooked up, I was told that went to the volt gauge in the stock instalation and since I dont have a volt gauge I dont need this wire.

With the car off the battery reads 12v. With the car on the battery reads 11 volts.

The car wont charge when its on and idleing. The car is on jackstands, so I cannot drive it to build RPMS, but I can rev it up.

I figure the problem is one of 4 things:
1. The alternator is hooked up wrong.
2. The alternator is bad.
3. The alternator is reverse rotation, if there is such a thing.
4. I am not getting it revved up enough to start charging.

Thoughts? Any advice is appreciated.

 

i run the same alt. on my race car.. i will have to check but if i remember right the small wire needs to have key power and run through a light.. so the light will be on when its not charging..

 

Hey-F is for "field" or the magnetic field which causes the alternator to produce electricity. If it isn't hooked up, you get no field, and no juice. Try running switched 12V to both L and F, and it should charge like a champ!

 

I am pretty sure the F is a field wire and in order to charge you have to power the field with 12V from the ignition switch,,,,,but if you hook the ignition switch up wrong the engine will not shut down when you turn off the ignition, the alternator will keep the coil activated,,,,,so I think you hook the field wire to the accessory side of the ignition switch so when you turn off the switch the engine dies and the alternator is de-activated..

 

Both of the smaller wires should be hooked up ,, one of them is a constant 12v at all times you can jump it off the heavy 12v wire lug and the other is a 12v with the key on ....Hope this helps!!!

 

I have the Field wire going to the ignition switch, thru a diode so that it will kill the motor when I turn it off. I tried hooking the F wire to the main lug so that it gets constant power, and that didnt help. Then I tried hooking the F wire to the ign switch with the Field wire. That didnt help either.

 

Sounds like you have it hooked up so that it should work.Make sure your diode is hooked up in the correct direction. The F terminal is the sense wire. It should go to a point where the loads are distributed. That is usually the feed where it enters the fuse box . I have seen cases where where a resister is also needed along with the diode on the L line.It is normally connected to a charge light with the bulb giving the circuit resistance. I usually put a 10 ohm 1\4 watt resister in line with the diode to simulate the bulb. If all else is good you need to consider the alternator as possibly being bad.

 

So the wire that goes to the L needs to have a light in line. But where does it go after that? Ground, 12v+?

 

It doesn't need a light if you use the resister and diode.It goes to switched power... most likley to your ignition switch.

 

Ok. I tried that with a bulb from a gauge. It still doesnt charge. I am starting to lean towards a bad alternator...

 

Yup....sounds like it might be bad.The internal regulators sometimes go bad.They can be replaced.

 

I think you have a CS130 alt.
Bat to the screw terminal.
S terminal goes to 12 volts all the time. It may be connected to 12 volts internally.
F terminal goes to switched 12 volt, usually the ign switch. F terminal doesn't have to be connected if you use the L terminal with a light.
L is for the light. Usually a switched 12 volt, thru a light and then onto the L terminal.

 

I hooked it up like that and got nothing. Looks like its bad. I may go get a cheapy $29 special from O'rileys to use until I can save up some $$$ for a good 1 wire.

 

I had something simular with my alt. and it ended up that the plug was'nt making good contact . bought a new plug , works fine . I will say that GM is proud of those plugs $$$$

 

Wow, what a relief; I thought you must have exceeded your credit limit...

Looks like your getting some really good info here, so I'll shut up

 

I just wanted to say thanks for all your guys help. I ended up getting a new 63 amp alt for $29 from the local parts store. I installed it and it pegs the gauge on full charge. Problem Solved!