California 1965 Buick Riviera + 1965 Ford F100

Dealing with a dead battery

Update: Drain is not fixed. Fully charged battery, removed charger and let sit for 5 days. At the end using multi-meter voltage read 4.x volts – I assume it suggests the battery is toast? The battery charges OK and driving around keeps it charged.

When I got the car, it fired up directly off the flatbed. I played with it that night and I believe mistakenly removed the key in the left accessory position. Didn’t have an owner’s manual and forgot how older cars worked. The next day, it wouldn’t start although there was some juice in the battery. I decided to buy a jump battery, which I used to successfully jump it and drove around for 15 minutes. However, 4 days later it was totally dead. Jumped again, worked. Next day, dead again.

Must be a parasitic drain issue. I decided I need to buy a multi-meter and also a battery charger and maintainer. Figured that until I figured out the parasitic drain issue, I’d want to keep this thing on.

I let it charge overnight, probably a good 20 hours to get it fully charged. I then decided to see what I could figure with the drain.

I disconnected the negative terminal and put the multimeter between it. Showed something a 0.485 amp drain, which didn’t seem like a lot. However, I noticed that every time I connected the negative terminal, I could hear a clicking noise, like a relay coming from the engine compartment. A quick search suggested this could be the horn relay. Now I know the horn works, so not sure what was going on.

Drain on battery

Next I disconnected the two horn wires from the horn… horns?… just to see what would happen. At that point the relay clicking stopped and the multimeter should no drain. Hmm… I then tried to reproduce the original issue by reconnecting the horn wires. But still no drain. So I thought maybe I’d shorted something out but went to test the horn and sure enough it still worked.

So a working horn, no measurable drain. I’m going to leave the battery charger off now and check it in the morning then over the next few days to see if it changes the outcome. No idea what removing and reconnecting the horn wires would have changed anything, though.

Once the battery is under 12v its basically under 50% charged. https://tontio.com/auto-guides/car-battery/car-battery-voltage/

Stuff List

Figured I’d keep a list of all the stuff I’m accumulating

ca65riv