battery drain

[kwplot34]

New member here. I have an 85 K10 Silverado. It has a battery drain if I let it sit for 2 weeks the batt will go dead. disconnected the neg batt cable and put a digital meter between cable and batt. Has a 2 amp draw and showing 12.8 volts. Had a friend watch the meter while I pulled the fuses, draw never went away. Anyone have any suggestions on where to look? Just changed out the motor a week ago, inspected wiring harness and re-wrapped the wires, saw no damage, all connections are clean and tight, pulled the 2 wire connector to alt to check it for the draw, no problem there.

 

[350runner]

You might have bad diodes in your alternator which will drain the battery after the engine has been shut off.

Sent from the dust in front of you!

 

[kwplot34]

You might have bad diodes in your alternator which will drain the battery after the engine has been shut off.

Sent from the dust in front of you!

Nope. disconnected the alt. still has the drain.

 

[yevgenievich]

There is power distribution block on the firewall. Can disconnect those wires one by one

 

[kwplot34]

There is power distribution block on the firewall. Can disconnect those wires one by one

That's worth a try. thanks

 

[Georgeb]

I noticed you said you disconnected the two wire connector from the alternator but what about the single 12 gauge wire that runs to the battery? Thats what was meant when bad diodes were suggested.

 

[87scotty]

Might be dumb but battery is good?

 

[kwplot34]

I noticed you said you disconnected the two wire connector from the alternator but what about the single 12 gauge wire that runs to the battery? Thats what was meant when bad diodes were suggested.

I will give it a try thank you

 

[kwplot34]

Might be dumb but battery is good?

Battery is good.

 

[chengny]

If the battery only discharges while the truck is idle - and stays in a charged condition while the alternator is operating - that would kind of eliminate a blown diode set.

There is one hot lead that does not pass through the firewall junction block. It runs straight from the starter to the cable transit. On the cab side of the transit it splits off and heads in two directions.

One lead runs to the far left bank of the fuse block (the BATT group) - if there is a clock installed it plugs in that bank. So does the DOME/CARGO lamp circuit. There could be something in either of those circuits that might pull about 2 amps - and yet not blow a fuse. Try pulling the plugs out of the sockets and watch your amp draw.


The other branch of that battery feed goes to the headlight switch. Except for the actual head light lamps, all the circuits that are supplied by the H/L switch are - at some point in their run - lead through the fuse block. So presumably pulling one fuse at a time would have detected the phantom load.

That leaves only the headlights and associated wiring. That circuit is protected by an internal circuit breaker within the H/L switch. Problem is - it doesn't open unless the current exceeds 6.5 amps. Your drain is not great enough to trip the breaker - and there is no fuse to pull. You might want to just pull the harness plug from the switch body and note whether the drain goes away.

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[kwplot34]

If the battery only discharges while the truck is idle - and stays in a charged condition while the alternator is operating - that would kind of eliminate a blown diode set.

There is one hot lead that does not pass through the firewall junction block. It runs straight from the starter to the cable transit. On the cab side of the transit it splits off and heads in two directions.

One lead runs to the far left bank of the fuse block (the BATT group) - if there is a clock installed it plugs in that bank. So does the DOME/CARGO lamp circuit. There could be something in either of those circuits that might pull about 2 amps - and yet not blow a fuse. Try pulling the plugs out of the sockets and watch your amp draw.


The other branch of that battery feed goes to the headlight switch. Except for the actual head light lamps, all the circuits that are supplied by the H/L switch are - at some point in their run - lead through the fuse block. So presumably pulling one fuse at a time would have detected the phantom load.

That leaves only the headlights and associated wiring. That circuit is protected by an internal circuit breaker within the H/L switch. Problem is - it doesn't open unless the current exceeds 6.5 amps. Your drain is not great enough to trip the breaker - and there is no fuse to pull. You might want to just pull the harness plug from the switch body and note whether the drain goes away.

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This great info. truck does have clock and it works, wouldn't think that would cause the issue. Alt charges good while truck is running, no issue there. I will pull the connector off the back of the light switch and see if that solves the issue. thank you for the reply.

 

[chengny]

I'd do the clock first.