Help, ideas, battery drain 79 K10 details

[Mike Curtis]

I replaced the motor in my dads 1979 K10, it sat for years so not sure but I don't think this was a problem before the motor went bad and it was parked.

The battery drains after a few days, I disconnected the ground connection at the battery and put a test light in between. The test light went on so I know I have an issue.

Next:
-I connected the test light to the battery ground and against the front core support, light still on, this way the ground cable from the engine is not connected to anything.
-with the light still on, I removed every fuse inside the cab, one at a time, the light never went out.
-with the light still on, I removed removed the 7/16 nut on the starter solenoid, on this lug is the cable going to the battery and 2 wires coming off the same lug. With only the battery cable connected to the starter, the light is out, when I put the 2 smaller gauge wires on the connection the light comes back on.
-up to the alternator, I unplugged the 2 wire connection on top of the alternator and the light goes out.
-I plugged it back up, the light comes back on, I removed the nut and wire on the back of the alternator, I think this is the power, the light still stayed on.
-I reconnected everything on the alternator, then split the 2 wire connection on top, the lug on the drivers side (redish wire) will cause the light to go out when interrupted. The other wire on the left had no effect.

Since the fuses couldn't isolate the short, and from what I describe, any ideas? The ground cable from the battery to the block is secure, and tight. The positive cable from the battery to the starter is not touching anything.

 

[dvdswan]

Have you traced the red wire or looked at the wiring schematic for the truck? Only a few items are hot all the time. Does the truck have a factory clock?

 

[4WDKC]

put the light between the battery and the cable, the remove the clock fuse as we know that will always draw on the battery. Once that is removed remove one fuse at a time checking the light every time you remove a fuse.

 

[HotRodPC]

My buddies truck had the same problem. I told him for months it was probably his stereo because he rarely drove it and he had the IGN wire of the stereo hooked up direct as well as the BATT wire that's keep powered up to save your memory stations and clock. He finally listened to me and disconnected the stereo IGN wire and after sitting for 2 weeks it started right up. His stereo system had a built in amp so it drew more power than most other stereos.

 

[Mike Curtis]

The truck is all stock, factory radio. no clock. I removed every fuse from the fuse block and the test light never went out. I did not remove the flasher relays, could that cause it?

Thanks for the ideas, keep it coming if you have others.

 

[Preston]

Would love to see some pictures of your truck

 

[4WDKC]

My buddies truck had the same problem. I told him for months it was probably his stereo because he rarely drove it and he had the IGN wire of the stereo hooked up direct as well as the BATT wire that's keep powered up to save your memory stations and clock. He finally listened to me and disconnected the stereo IGN wire and after sitting for 2 weeks it started right up. His stereo system had a built in amp so it drew more power than most other stereos.

most stereos have a built in amp or there would be no sound coming from them. if he wired it wrong so it was always on it would drain the battery.

Check your dome light also as it could be staying on and draining the battery.

 

[4WDKC]

when you replaced the engine did you use the alternator from the truck on the one for the engine? Older cars didnt have an internal voltage regulator and if you used an older alt that will drain your battery, thats how I learned about it.

 

[HotRodPC]

most stereos have a built in amp or there would be no sound coming from them. if he wired it wrong so it was always on it would drain the battery.

Check your dome light also as it could be staying on and draining the battery.

I should have said bigger amp. It's big enough there's a heat sink on the back of it he claims.

 

[Mike Curtis]

when you replaced the engine did you use the alternator from the truck on the one for the engine? Older cars didnt have an internal voltage regulator and if you used an older alt that will drain your battery, thats how I learned about it.

I had a guy replace the engine, so I'm not sure. It's a 3 wire connection from the alternator and the motor combo came out of an early 80's truck. My best guess is they are the same. Only 3 wires connected to the alternator. 1 bolted on the back and the 2 wires in the plug.

 

[Wumbo]

It's the alternator.

 

[Mike Curtis]

It's the alternator.

Is there a way to test it? Or if I take it off can they test it at the parts store? Or, is this something that has to be on the truck running to test?

 

[Mike Curtis]

Is there a way to test it? Or if I take it off can they test it at the parts store? Or, is this something that has to be on the truck running to test?

If the alternator is bad, will it short out and cause power to be in the ground? I can measure voltage in the truck radiator support.

 

[Wumbo]

If the alternator is bad, will it short out and cause power to be in the ground? I can measure voltage in the truck radiator support.

Yep

Leaking through brushes/armature to ground



Radiator support to what, negative battery terminal? The radiator support should have 2 ground wires, maybe 3. There should be a ground under the headlights, and one going from the core support to the frame on the passenger side.

You shouldn't see any voltage there.

 

[Wumbo]

Is there a way to test it? Or if I take it off can they test it at the parts store? Or, is this something that has to be on the truck running to test?

Not sure what they test at the parts stores. I've heard of alternators that put out a charge, but when the engine is off they drain the battery through the brushes/armature.