Battery drain issue
 

Working through a wide range of gremlins on my '64 C10 and the overnight battery drain issue is driving me nuts. I realize there are a ton of threads on this topic, just looking for some reassurance I am on the right track.

This truck sat since '98 before I acquired it recently and had a wide range of "interesting" electrical hack work done including the use of a ton of wire nuts. Thus far, I have installed the following new electrical parts: both under hood harnesses (starter/distributor & alternator/main cab feed), voltage regulator, horn relay, alternator, battery, and battery cables. And in the the cab, new light switch and heater switch. I also redid/replaced the main ground straps (chassis to fender, cab to chassis, motor to firewall). The charging circuit seems to be working normal as I am measuring 14.2 volts while the truck is running and the truck remains running with the battery disconnected.

My first overnight test on Sunday was disconnecting the drivers side engine harness from the firewall and the battery voltage was unchanged overnight. Next step was attaching a test light in series with the positive battery cable and with everything connected, it was lit. So I started disconnecting just about everything in the dash starting with the ignition switch, then each fuse and wire from the fuse block with no change as the test light stayed lit.

Could this be something in the fuse box itself? It does look very crusty, but seems odd that nothing changed with everything disconnected. I recently ordered a new dash harness from Classic that includes the fuse box, so that is next on the swap list.

Open to any other ideas or feedback. Thanks!

Re: Battery drain issue
 

Try disconnecting the engine harness at the firewall. Or disconnect the red wire at the alternator.

Re: Battery drain issue
 

^ Yup. I had two rebuilt alternators in a row drain my battery.

Re: Battery drain issue
 

Thanks all.

Confirmed that prior and with the drivers side harness unplugged at the firewall there is no drain as well. But in good news, think I figured it out. Shortly after typing up the original post, it hit me that I totally forgot about the passenger side harness. So I unplugged that harness at the firewall and what do you know, the test light was not lit. Next up was reconnecting and checking the coil and temp gauge sensor... neither extinguished the test light. That only leaves the starter solenoid, which I am confident is the culprit. The starter works fine, but assume a partial short in the solenoid is still possible.

The heat wave is rolling through now, so I will confirm it later along with picking up a replacement while in town tomorrow. It will be nice to put this issue to bed as there are plenty of other areas to attack with the leaking radiator up next, followed by getting a bed installed so this truck can get put to use.

Re: Battery drain issue
 

It could be as simple as the yellow wire that feeds the coil touching the main battery cable. Though that generally means the engine doesn't shut off when the ignition switch is turned off.

Re: Battery drain issue
 

Good idea, but the drain issue was present before I installed the new passenger side engine harness as I originally thought the drain was with the old alternator and the truck starts/turns off normally.

I will double check though before pulling the starter.

Re: Battery drain issue
 

I had a similar problem on my 64 C10. If the problem is still present and your truck has the external voltage regulator, I would check it to make sure that it is operating correctly and not stuck closed.

Re: Battery drain issue
 

have you confirmed that the horn works? you may have replaced the horn relay but if the horn is non-functional, the horn ring in the steering wheel may be engaged/depressed thus activating the horn relay but if the horn isn't working, battery drain.

Re: Battery drain issue
 

No horn, but confirmed that was not an issue early in the TS process.

Re: Battery drain issue
 

Make sure the top of the battery is clean, you can get a drain if there is current flowing between the post from buildup of gunk.

Notice where the positive lead is touching...

https://i.imgur.com/gIw1bxHh.jpg

Re: Battery drain issue
 

YUP! When I worked as a mechanic and people came in with dead batteries, I'd put the voltmeter on them like that, but the battery was filthy dirty, and damp. I'd show them the voltmeter reading and then clean the battery top. If the battery was actually bad, I had a sale. If it wasn't, they would trust me later for a sale.

Re: Battery drain issue
 

did you resolve the battery drain?

Re: Battery drain issue
 

Yep. Finally had some time last night after a long weekend with family in town to continue the process of elimination. Removed the yellow & pink wire from the solenoid R terminal with no change. Since I already tried the ignition switch previously, I assumed the purple wire (from the solenoid S connector) was not the culprit and tracked the black wire to the ammeter on the instrument cluster. Once unplugged, the test light was finally out!!

No change overnight to the battery voltage, so it appears I have an issue with the ammeter. What an ordeal and one that was compounded by all the various wiring diagrams in the assembly manual and needing to find the right one for a V8 with gauges.

Thanks for all the ideas!!

Re: Battery drain issue
 

thanks for the update. good job!