47-55.1 Parasitic drain

[8man]

I have a parasitic drain running down a battery over the period of a week. I pulled out the multi-meter and checked the millivolt flow across all of the fuses. Only 2, the Horn and the Hazard, had a flow and it was over 350 millivolts for each one.

I'm at a loss on how to proceed from here. The horn only honks when I push on the top of the horn button and the hazards are not flashing, but work a do the turn signals.

Any help is appreciated.

[8man]

Disconnected the steering column harness and still had the drain.

I think that means I have to check the wiring to the horn, it runs through a relay, so I'll check that, but the flashers is still a mystery.

[mr48chev]

Do this before you go much further. Take your multi-meter and check across the top of the battery in several areas.

Connect the positive wire to the positive post and take the tip of the negative wire and touch around on the top of the battery to see if you have power draining off across the top of the battery in any dirt or moisture that might be there.

When I was teaching auto mechanics one of my student's truck would have the battery go dead in two and a half hours sitting in the parking lot. We would jump it, run it around to the shop and stick the charger on it and charge it and it would start right up and it charged right on the money. About three days of that and we made it a class project to figure it out. We found out that we had 9-1/2 volts indicated at one spot on the battery top. They washed the battery off and cleaned up around it and no more problems.

Had another student with 64 Chevy lowrider who was having dead battery problems when he got ready to go to school in the morning. He worked in a grocery store and left the car at home so it wouldn't get door dings in the parking lot. after about a week of jumping it every morning and going every thing electrical in the school shop his mom says "oh your little brother and his friends listen to your sterio every night when you are at work". He never said how long it took for his brother's bruises to fade away but he didn't have any more battery issues after a rather one sided discussion with him.

Still you should be able to hook up a multi meter in the negative cable and have it set on amps to see if you have a draw.

[dsraven]

-check your alternator as well. lots of times the alternator is the cause. pull cable off the alt and install volt meter between the output stud and the cable. should read zero.
-check the stereo because they can also be the culprit. had that problem last year with my boat. drained battery overnight. they will have a parasitic load if they have a clock or memory.
-pull "hot with key on" wire off ign switch and check for a draw. not unheard of to have a faulty ign switch feeding circuits
-check wiring harnesses for mechanical damage. especially around hot things like exhaust.
-check the back side of the fuse panel for anything that looks odd. I had one that had a poor connection at one of the crimps and it melted the panel a bit over time so the panel distorted and allowed some cross feeding of circuits that meant a parasitic load with key off.
-if you have a trailer hitch plug check that as well. plenty of those have caused problems before
-check starter connections and/or disconnect the battery cable to check for a draw through the solenoid internally
-disconnect battery ground
-connect voltmeter between battery and ground cable
no load would mean zero volts. obviously that won't be the case since you already know you have a parasitic draw
-pull fuses, one at a time, while watching the volt meter. an old fashioned analog meter works best for this because it won't "auto range" or keep scrolling through numbers when the voltage changes by a decimal point.
-when you pull a fuse and the voltmeter reading changes then that indicates a draw in that circuit
hopefully you find it. post up the cause when you do.

[8man]

Thanks guys. I found my offending circuit. I took another manufacturers under hood fuse box and rebuilt it for my use. I have a 30 amp fuse running the power windows and seats. When I pull it out, the drain stops.

So now that I know which one it is, I just need to figure out why its got a current. It isn't enough current to be a dead short, which I had in the dome light and it blew a 20 amp fuse when I plugged the fuse in.

I know it runs power to relays for the window motors, so I'm thinking that maybe a relay might be going bad.

Any other thoughts?

[dsraven]

Unplugged relays at the seats and see if you still have a draw. If you still have a draw it's somewhere between the battery fuse box and the seats. If no draw with seats unplugged you know it has to be in the seats.

[dsraven]

If you find that it is in the seat wiring, relays, whatever. Unplug one relay at a time or one motor at a time or one actuator at a time, and see which one makes the draw go away. Do all this after first checking that the wiring to the relays is all intact and wired properly. Also ensure that you have a proper ground for those circuits in that setup.

[8man]

Thank you.

[mr48chev]

It looks like the simple way is to remove one relay at a time and do some eliminating.

I'd agree that it isn't a direct short or you would have something getting hot. Or drawing enough current to blow a fuse or kick a relay.

Keep us posted as this is becoming an educational experience for all of us. Trouble shooting is always a process of elimination and that starts with the simplest things and works to the complex things most of the time.

[8man]

We have family this weekend, but I was able to check relays to the two side windows and the two for the door locks. While none of them was the culprit, I did discover that the drivers door lock switch was not working, so I fixed that while I was in there.

We have more family tomorrow, and then next week I'll check the two power seats to see if there is a draw there.

[dsraven]

check your relay wiring to ensure you don't have a relay that is wired to energize in order to stay open or closed. maybe the parasitic drain. if you unplug it and it clicks then it was energized and would have a load or some sort. relay solenoids are wound with small wire, many windings, small draw. sorta makes sense. wouldn't that be cool to find. something easy.

[mr48chev]

Originally Posted by dsraven

check your relay wiring to ensure you don't have a relay that is wired to energize in order to stay open or closed. maybe the parasitic drain. if you unplug it and it clicks then it was energized and would have a load or some sort. relay solenoids are wound with small wire, many windings, small draw. sorta makes sense. wouldn't that be cool to find. something easy.

That may be the best suggestion of all. It also makes a lot of sense in this case.