The Stovebolt Site Forums The Shop Area The Electrical Bay battery died

1966 C10 that has a 350 and an electric fan. My battery died, so I had it towed home. Turned out to be a bad battery, so I replaced it. Then it died again, thinking it was the battery connection. I replaced the connectors and did a better job of it. I also thought maybe the alternator, so I changed it, but there was still a warranty. Then it died again, so I changed the voltage regulator and then the horn relay. There still isn't a charge going to my battery. Is there anything else I can check? The alternator wire was melted a little, but I didn't know until I changed everything; maybe two wires were melted together. I'm replacing them next.

Thanks for the help.

There are two common reasons for repeated battery failures- - - -charging system problems that prevent the battery from being recharged properly, and "parasitic drain" which is a constant small current draw that drains the battery slowly when the engine isn't running. Are you using the original charging system with the alternator and regulator as separate units? if so, that was a pretty bad system when it was new, and it certainly hasn't improved during the past 60 years. I'd suggest switching to the 10-SI internally regulated alternator that came along about 1970 or so. Check for parasitic drains by disconnecting the ground cable at the battery and touching it to the battery post. If you see a spark, even a tiny one, you've got a constant current drain. Find it and fix it.

Throwing multiple parts at a problem without diagnosing it first is like a doctor writing prescriptions without examining his patient!
Jerry

Do you have an externally mounted voltage regulator or is your alternator internally regulated?

Externally mounted

The Doc.

Hy climberman, as Hotrod Lincoln so often says, we need to test not guess! Throwing parts at a problem without knowing what the real problem is can get expensive and be very frustrating. You need to see if you are getting any charging happening at the battery. We would need a lot more information to help you fix this problem.

Well, things happened at different times. First, the battery tested bad, so I bought a new one. A week later, it went dead again. Summit Racing sent me a new alternator on warranty. I didn't know about checking the voltage at the battery to see if I'm getting 14 volts, now I do, and I only get 12.64 when the motor is running. I didn't notice the burnt wires until after I did everything else.

One easy test my Dad used was start the engine and while it is running unhook one battery cable.
If the engine dies it's the charging system, if it stays running it's the battery. That will at least give you a start on chasing down the gremlin that may be draining the system.
Like Jerry said, an internal regulator is the way to go.

Don

I tried the battery trick by accident, and when I disconnected the ground, the motor died.

That trick about pulling a battery cable to check a charging system went out of favor at least 40 years ago. The voltage spike from the charging system as the connection is broken can destroy thousands of dollars' worth of computers. I've had an oscilloscope on an electrical system to demonstrate that to my students. When a battery cable is disconnected with the engine running, I've seen spikes in excess of 100 volts DC. That can fry lots of computer circuits on anything with solid state components, including an electronic voltage regulator.
Jerry

Good info Jerry, I did not know that. Dad showed me that back in the early sixties before all this computer crap.
I learn something every time you post!

Thanks
Don

I'm glad I know that now because I have newer cars, but my 66 doesn't have a computer. It does have a voltage regulator. Do you think I fried it?

Rocky

Is it a one or two wire ALT? Self exciting? Check voltage at the Positive battery terminal and make sure its charging.
Wires should be 10 gauge

No. You're safe in the pre computer era.

(Is it a one or two-wire ALT? Self-exiting? It is a single wire.) The voltage at the battery is 12.65 with the motor running.

12.65v at the battery at idle means your system isn't charging at all. Should be 13.5 to 14.5 volts

How do you test an external voltage regulator to ensure it is functioning properly?

Do you have a shop manual for your truck? It will explain how to test the voltage regulator.

Basically you bypass the VR by connecting the Field (F) or (FLD) terminal to switched power like the ignition switch. If the alternator charges the battery, the VR is most likely the problem.

Only do this for a short period of time so as not to overcharge the battery.

Thanks Otto
A crazy thing I asked ChatGPT that question, and it explained exactly how to do it, showing diagrams.

Rocky

With the glacially slow response of the forum lately, submit a post, go have an adult beverage or two, and come back to see if it appears. That will avoid multiple posts on a thread. Don't waste much time on that antiquated external regulator setup unless you're running a "numbers-correct" show truck. Something as simple as a burned out idiot light bulb can keep it from working. Upgrade the alternator to a 10-SI.
Jerry

Hotrod

I looked up a diagram for that, not sure I can get that done right.

It takes a grand total of three wires, and maybe an indicator bulb if you want to have an idiot light. PM me and I can send you a simplified wiring diagram that works- - - -first time, every time.
Jerry