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Brand new alternator draining battery?

Brand new alternator draining battery?
B

brtc

Jeeper
Posts
10
Thanks
0
Location
Mary Esther, Florida
Vehicle(s)
1975 CJ5-258
Hello, thanks in advance for the help. I've been working on this problem for a few days now and can't figure it out. I bought a brand new battery and a few days later, my jeep wouldn't start. With the jeep off, I pulled the negative, hooked up a multimeter between the battery and the neg cable and saw it was reading a voltage. I narrowed it down to the alternator. Changed the alternator and even with the new one, it is drawing power. Is there a ground or something I might not have hooked up? I just got the jeep so there's no tellin how much work I'll be doin to it. Thanks.
 
My first checks would probably be loose alternator belt, loose battery cables, corosion on the terminals. Not certain that an alternator can drain a battery. Just not charge it very well. How old is the battery?
 
Thank you. The battery is brand new. The alternator is brand new. And when the Jeep is off, the battery is getting a constant drain. When the alternator lead is connected, I get 8 volts with the jeep off. When it is disconnected, I get 0 volts. So, the the alternator is somehow drawing power. My first assumption was a bad diode, but with the new alternator, I have no idea
 
brtc said:
Thank you. The battery is brand new. The alternator is brand new. And when the Jeep is off, the battery is getting a constant drain. When the alternator lead is connected, I get 8 volts with the jeep off. When it is disconnected, I get 0 volts. So, the the alternator is somehow drawing power. My first assumption was a bad diode, but with the new alternator, I have no idea
Click to expand...

Can you explain a little better how you are getting the voltage readings? What is your battery voltage with the engine off? Are you connecting one test lead to the large alternator post and the other test lead to ground to get the 8 volt reading? What is your voltage when the engine is running and all of the accessories (lights, fans, etc. off)?

Are you reading this voltage on a multimeter or a gauge inside the Jeep?

Just trying to figure out what you are testing with and if we can help solving the problem...

:chug:
 
Here's some pictures. This jeep is a wiring nightmare. It's a 1975. Just picked it up a few weeks ago, didn't realize the amount of problems it had. Anyway. The battery reads 12.4 volts with the engine off. When it's on, it was a little over 13 volts. When the negative post on the battery is disconnected to the cable, I connect the multimeter between the negative post on the battery, and the negative terminal cable (with engine off). I get a reading of about 8 volts, only when the alternator is connected. As soon as I pull that plug in the picture (on the alternator), I get zero volts. I just pulled every fuse, and the multimeter still reads about 8 volts. I even disconnected the external voltage regulator, and still 8 volts. I am stumped on this one. Thanks for the help.
 
I am a bit stumped also, what I see looks like a GM 10si alternator which is internally regulated. Looking at a '75 CJ wiring diagram it shows a Motorola alternator with 4 wires coming out of it with 3 going to the external regulator, and the 4th going to the battery. Where is that what looks like a black w/tracer wire going to? actually the pics look like it is wired for an internal regulator.
 
Thanks Torxhead, I noticed that as well. That black wire is going to the fuse block. It is a single piece of wire, unlike the rest of the wire. I'm having trouble figuring out what is original and what is not in this harness. That red wire was originally hooked straight to the positive terminal on the battery. I tried hooking it up to the starter solenoid and still no fix. I even went to autozone and got a new alternator connector.. Spliced that in and still a bust. I need to get the tranny back in the jeep so i can start the motor. clutch comes in monday.. I want to see if I disconnect that black wire, if the alternator will still charge the battery. Even with all fuses removed, I still get 8 volts, so I have no idea where that black wire is grounding in the fuse box.
 
So I"m a rookie. I'm having the same issue with my Scrambler draining the battery. Ive owned if for about a month with no issues. Then took it in to get the Transfer Case seals replaced and u- joints replaced. When I picked it up they said they had to jump it and now it keeps draining the battery. I replaced the Alternator but that didn't change anything. Did you guys ever come up with a solution from the post above???
 
They make one wire alternators that do drain your battery thru regulator internal, we use them on airboats all the time but we have marine battery switch that you must turn off. Any good alternator shop can modify a one wire alternator to not drain the battery cost about $40.00 to do. Just had one done on my Mast LS7, got tired off turning off the battery switch. Or run the two wire thru the key switch like my 82 has:)
 
Thanks, It had a delco alternator in there.Thats what it calls for so thats what i put back in. There is a small brown wire that wasn't connected. When i hook it up the wire the jeep won't shut off. So Thats another issue.
 
Looks like your in Fla so I can give ya my alternator shops number he can help you for sure, Mast said could not fix the alt draining thing he did it in about 2 hours, sounds like you going to have to run the wires out, just get wiring diagrams from factory service manual and straighten out your harness, good luck
 
Here is a link I posted in the other alternator thread
Wiring up the GM 10SI Alternator

I always run the #2 terminal through the ignition switch so all power to the alternator is cut when the switch is off or on acc. Do you still get battery drain with just the #2 terminal disconnected? And lastly, just because something is new or a fresh rebuilt doesn't mean it actually works. And that includes both batteries and alternators.

Also, I wasn't aware that the one wire versions caused any battery drain. I have several diesel tractors with those and they can sit all winter without draining the battery.
 
Hmmmmm, my one wire regulator doesn't seem to draw down my battery. I asked about such thing and the alternator rebuilder didn't mention a battery draw down problem.
 
One, two or all three POs of my Jeep hacked into the factory wiring, drawing current from here and there, mounted electrical consumers in the engine bay, never finished the install and left 1/2 wired components bolted to the fenders.

I discovered a parasitic drain and after pulling all the fuses, I determined that it'd be easier to just install a new chassis harness.

It was hell getting everything back to a known quantity, but having wiring you trust is pure gold.

-Jon
 
That's sounds like good idea, the one wire alt I am talking about only have the wire to the battery, no other trigger wires. the plug is blanked off but anyway sounds like you got a good plan
 
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