SpeedJunkie

I have a 88 TPI, I have been chasing a battery drain and with the plug in the alternator it is grounding itself out. I tried a new alt last year and it was the same. IT is a faint light drain but the tan/white wire in the 3 wire plug has constant voltage. It is faint when plugged in and when i unplug it and ground that one wire it completely tranfers all 12 volts.

So, does the tan/white wire always have voltage or is this suppossed to be igntion run only? Where does this wire connect to the Ignition or the fans? I need to chase down this short or drain and I have read and looked at every post/thread/and wiring diagram and cant track it down.

BigBadLou

iTrader: (3)

For your year/model vehicle, the alternator should have a tan wire, not tan/white. No matter, that tan wire should have power to it only with ignition on.

This wire is spliced in the harness under the fan relays on the firewall (by the brake booster). The two fan relays might have a tan wire or it might be a brown wire (talk about GM confusing the mechanics!). Check those wires on the fan relays. If they have power too (with key off), something's probably amiss with your ignition switch. You can also check the pink/black wire on the coil for power.

Good troubleshooting, btw.

Hope this helps.
Lou

SpeedJunkie

Lou,

I did think that with the ignition switch and actually dropped the column and unplugged all the connections to the column/ignition switch. I also when trying to find the short/drain unplugged almost every relay and modules including the 2 relays by the brake booster.

If what u are describing is accurate, where does the red and other "brown" wire go that comes from the plug? If I cut the wire that has voltage and run a new ignition only "key in run" wire to the alternator plug what will be affected?

Thanks so much for your help too!

BigBadLou

iTrader: (3)

I see I might have made a wrong assumption here.
I thought that your alternator had the standard two red wires and then the tan wire. But it seems that instead, it had a red wire, tan/white wire and a brown wire.
The brown wire is actually the one that should be powered by the ignition in that case. The other two wires in the plug are always under power (from the battery). But they should not create any drain throught he alternator with the ignition off.

If you disconnect the alternator plug, does your battery drain stop? If so, it would point to a bad alternator. If not, the drain is elsewhere in the vehicle.

How big is your drain?
Did you put an ampmeter on the wire from the battery? Is it in amps or milliamps?
Did you try pulling every single fuse in the fuse holder under the dash?
Did you remove the radio or CD changer or amp and such?
Did you try pulling the ECM/fan/fuelpump fuse by the battery?
Did you unplug the ECM?
Did you maybe try unplugging the C100 on the firewall?

I know, so many questions. But I hope they help you find your answer!
Lou

SpeedJunkie

Yes the tan/white wire has fl voltage, the red wire does not though. If I pull the alternator plug it stops. I am pulling about 300 milliamps.

I have tried a new alternator last year and it was the same
I pulled every fuse and the fan fuse make it drop slightly by about 100 milliamps,
The radio and all amo connections are disconnected
I did pull the fuse by the battery and it also drops slightly also. Even with the other fan fuse out it drops slightly but still has a drain
have not tried the ECM, but if that is unplugged and goes away what would that mean? I don think the ECM is sticking on after being powered on.
C100 nope, is that the large one that travels through the drivers side firewall?

I had this problem about 2 years ago when I started to disassemble the entire front end. I took everything down to the shell and redid everything. I cleaned every connection and made all new grounds on the back of the block.

BigBadLou

iTrader: (3)

Yup, 300 mA through the alternator is too much. The alternator should draw nothing with the key off.
I wonder if the problem is the red wire that doesn't have constant voltage. I have never seen this condition and cannot say what the alternator would do with voltage on one wire and not the other and it's hard to determine without knowing the internal connections in the alternator.

I would check all fusible links and connectors by the battery and on the starter to see why the alternator is not getting voltage on the red wire.
Charging circuit diagram here: http://www.austinthirdgen.org/mkport...8_charging.jpg

Hope this helps.
Lou