Battery Drain Help

[Jferrante]

Alright guys need some help. Freshly rewired 64 stepper with (AAW 500560 kit), new high torque starter and new battery - new wiper motor, new heater motor. Battery is drawing .9 amps with nothing on. Pulled every fuse and relay on the new fuse box and still pulling .9 amps. Started the truck and pulled the negative terminal and car ran fine so I am ruling out the alternator.

What else could be putting such a load on the system?
Thanks for your help as always

[ray_mcavoy]

Disconnecting the battery with the engine running won't rule out the alternator as a source of the battery drain.

Instead, you need to leave your ammeter hooked to the battery and see if the .9A draw goes away when you temporarily unplug the alternator (do this with the engine off of course).

Also, since this is a fresh rewire, it wouldn't hurt to double check your alternator connections. With an internally regulated alternator, accidentally crossing up the "exciter" and "voltage sensing" wires will create a battery drain yet still allow it to charge.

[Jferrante]

Originally Posted by ray_mcavoy

Disconnecting the battery with the engine running won't rule out the alternator as a source of the battery drain.

Instead, you need to leave your ammeter hooked to the battery and see if the .9A draw goes away when you temporarily unplug the alternator (do this with the engine off of course).

Also, since this is a fresh rewire, it wouldn't hurt to double check your alternator connections. With an internally regulated alternator, accidentally crossing up the "exciter" and "voltage sensing" wires will create a battery drain yet still allow it to charge.

Good to know - rookie here with electrical so I will try this and report back.

[bumwine]

Are you still running a external voltage regulator?

[Jferrante]

Originally Posted by bumwine

Are you still running a external voltage regulator?

No - newer style alternator (at least I believe) see the culprit below

[bumwine]

Oh ok. Was just curious. My voltage regulator crapped out after my rewire and drain my battery. Figured I'd ask lol

[Jferrante]

Originally Posted by ray_mcavoy

Disconnecting the battery with the engine running won't rule out the alternator as a source of the battery drain.

Instead, you need to leave your ammeter hooked to the battery and see if the .9A draw goes away when you temporarily unplug the alternator (do this with the engine off of course).

Also, since this is a fresh rewire, it wouldn't hurt to double check your alternator connections. With an internally regulated alternator, accidentally crossing up the "exciter" and "voltage sensing" wires will create a battery drain yet still allow it to charge.

Just ran out and checked the wiring and that was correct - then tested with just unplugging the alternator and bam .9amps down to .1amps - I think this solves it no?

[Ghernandez66]

I had that issue even though I have original wiring I realized the previous owner had installed an internally regulated alternator and never fixed the wiring by removing the external regulator so it keeped draining my battery

[jtrichard]

Read this it will tell you what is wrong (you most likely have a bad diode trio) http://forums.anandtech.com/showthread.php?t=2254082 the answer is in the first 4 post's



From another site... "A malfunctioning diode in the alternator can create a parasitic drain on a car's battery. Diodes should allow current to pass in only one direction, but a bad diode will keep the charging circuit open even when the engine in not running, allowing the battery to go dead. This often happens overnight."

[Jferrante]

Originally Posted by jtrichard

Read this it will tell you what is wrong (you most likely have a bad diode trio) http://forums.anandtech.com/showthread.php?t=2254082

Thanks - new alternator arrives today so hoepfully that does it. when i test the amp draw with the alt unplugged it dropped from 0.9 to 0.1 which led me to bad alt (diode or whatever)

[VetteVet]

Originally Posted by Jferrante

Thanks - new alternator arrives today so hoepfully that does it. when i test the amp draw with the alt unplugged it dropped from 0.9 to 0.1 which led me to bad alt (diode or whatever)

The recommended allowable current drain for vehicles is 2 or 3 milliamps .002 to .003. You may still have a draw. did you disconnect the large red wire on the alternator as well as the plug?

[Jferrante]

Originally Posted by VetteVet

The recommended allowable current drain for vehicles is 2 or 3 milliamps .002 to .003. You may still have a draw. did you disconnect the large red wire on the alternator as well as the plug?

Just the plug - will retest with the red wire removed as well before I install the new one.

[_Ogre]

jfyi... the way you have the plug connected makes the alternator self exciting, i have run many that way

but... since the rectifier or diode block went bad i would have replaced those parts for a lot less than a new rebuild
buying a rebuilt alt doesn't mean a new diode/rectifier, it just means it was tested good, the diode/rectifier may be 30 years old
rebuild kits are available for $23 that come with everything to make it a one wire alternator

http://www.ebay.com/itm/10SI-Delco-A...-/200674163004

[Jferrante]

Originally Posted by _Ogre

jfyi... the way you have the plug connected makes the alternator self exciting, i have run many that way

but... since the rectifier or diode block went bad i would have replaced those parts for a lot less than a new rebuild
buying a rebuilt alt doesn't mean a new diode/rectifier, it just means it was tested good, the diode/rectifier may be 30 years old
rebuild kits are available for $23 that come with everything to make it a one wire alternator

http://www.ebay.com/itm/10SI-Delco-A...-/200674163004

Thanks for the info - I just bought a brand new alt since I have already gone new everywhere else (starter, wiring, battery, and battery cables) - figured it was worth the investment to do it now and be done.

[Jferrante]

Good news- the new alternator got me down to the .12ish amps that I was getting with the old one disconnected. So the next part was to find the remaining culprit. Good thing it was quiet outside as I was testing the amps and completing the circuit I heard a relay switching on. Pull the horn relay and boom we are at 0 draw. Now the question is why was a brand new relay sticking in the on position? Next project LOL.
Thanks all

[VetteVet]

Originally Posted by Jferrante

Good news- the new alternator got me down to the .12ish amps that I was getting with the old one disconnected. So the next part was to find the remaining culprit. Good thing it was quiet outside as I was testing the amps and completing the circuit I heard a relay switching on. Pull the horn relay and boom we are at 0 draw. Now the question is why was a brand new relay sticking in the on position? Next project LOL.
Thanks all

If your horn relay was closed the horn should have been blowing assuming it was wired up.
The three wires going to the horn relay are 12 gauge red 12 gauge green and the smaller black wire. The red wire is 12 volts power directly from the battery and the green wire completes the circuit to the horn when the relay closes.

The red wire also provides positive voltage to the relay closing coil.
The small black wire is the ground side of the relay coil and when it touches ground the relay closes and the horn blows. The black wire is normally grounded by the horn button in the steering column. If the button is sticking, or the black wire is shorted to ground, it will close the horn relay. I suspect that the black wire is shorted in the column or at the horn button.

[Jferrante]

Originally Posted by VetteVet

If your horn relay was closed the horn should have been blowing assuming it was wired up.
The three wires going to the horn relay are 12 gauge red 12 gauge green and the smaller black wire. The red wire is 12 volts power directly from the battery and the green wire completes the circuit to the horn when the relay closes.

The red wire also provides positive voltage to the relay closing coil.
The small black wire is the ground side of the relay coil and when it touches ground the relay closes and the horn blows. The black wire is normally grounded by the horn button in the steering column. If the button is sticking, or the black wire is shorted to ground, it will close the horn relay. I suspect that the black wire is shorted in the column or at the horn button.

Horn isn't connected - I haven't touched my column wires so I suspect the black wire is shorted in there as you mentioned. Thanks for the help these help me troubleshoot it.