battery drain
 

On my 68 c10 I have a battery drain. I used a test light and found that if I unplug the wires to the alternator it will stop the draw. The alternator is new and the old one would do the same thing. Can anyone tell me what to do or try? Your help would be greatly appreciated!!

Re: battery drain
 

Weird... sounds like perhaps a shorted diode within the alternator, but in both? I don't know much about external regulators, but does it change if you unplug the regulator but leave the main power lead on the alternator, or vice versa?

I unplugged the wires that has the plug and left the one that has the eye connection with the red wires. My truck doesn't have a external regulator it's built in.
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Re: battery drain
 

You might check the core support by the driver side headlights to see if there's a regulator there.
Trucks of this age used regulators. You have to change the wiring a bit to use an internally regulated alternator.
You might want to snap a pic of the alt. and connections and search to see exactly what alternator you have.

Re: battery drain
 

It's has a new painless wiring harness but I will check for a external regulator but I don't think it has one.
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Re: battery drain
 

Did the painless harness come with the alternator plug pre-wired? Or did they just leave loose wires that you had to connect to the alternator?

The reason I ask is because the alternator's voltage sensing wire is live all the time. If that wire is accidentally connected to the alternator's exciter terminal (which is supposed to be switched on/off via the ignition) it will create a battery drain.

Like franken said, posting a pic of your alternator and it's connections would be helpful.

Re: battery drain
 

Ok guys I will post some pics in the morning. Thanks so much!
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Re: battery drain
 

I was wondering did this problem start after you installed painless loom if so you might check with them and make sure they built it for a internal regulator because these trucks had external from factory just a thought wire problems can be a pain sometimes good luck there is a fix either way

Re: battery drain
 

I ended up taking the alternator to a shop and got it tested. It was good so the guy changed it so I would have a one wire altenator system and this fixed the battery drain problem! Thanks for everyone's help!
Now if I can fix my other electrical problem I'll be good to go! I have no brake or hazard lights but do have signal and tail lights. I do have power to the brake light switch and I replaced the brake light switch. Any ideas?
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Re: battery drain
 

Remember your alternator light (or ammeter) will no longer work with a one-wire setup. Sometimes too you have to rev them past a certain point (like 2000rpm) to "light them off", but that could be old school tech.

On your brakes how far did you trace the brake light wiring back? What else do you know? Not anything to go on yet in your description.