Hi all,

My son has an '88 Firebird, with a 305 auto. We're trying to get to the bottom of a battery drain problem. If the car sits for more than a day, the battery (brand new) will be dead and require charging.
One symptom that may or may not be related: The radio led clock display stays on all the time.

Steps I've taken:
disconnected the positive battery cable, and used a multimeter to measure current between the battery post and the cable. It measures full voltage, even though everything is "off".

I unplugged the radio/clock to make sure that the clock display wasn't the problem. MM still shows full volts between the battery post, and the disconnected positive cable.

Inspection of the positive cable revealed it actually connected to several things, including the starter solenoid, a junction near the radiator, and a switched wire connected to the radiator cooling fan. Disconnected all three so I could measure voltage drain to each separately. The only one which showed the voltage drain was the main black positive cable connected to the starter solenoid.

Inspection of the cable revealed no grounds, or breaks. The positive battery cable connects to the same solenoid terminal as two large red wires, which appear to have fusible links near the starter. Disconnecting the additional red wires, resulted in no measureable voltage drop. Re-attaching them caused the voltage drop to return.

Seems to confirm that the battery cable is NOT the cause of the trouble. Tracing the red wires, I discovered that the one single wire connects to the alternator. When just it and the battery cable are connected to the starter, there is no measureable voltage drain.

Does anyone know what the other pair of large red wires connected to the starter solenoid are connected to at the other end? My first thought was the ignition switch, but unplugging all wires from the ignition switch resulted in no change in the voltage drain...

A few good things have come of this so far: I replaced a blower motor that wasn't working, fixed some really crappy splices, cleaned up the fan wiring, etc... Still no solution, but good anyway!

Any ideas??

 

everything youve measured is correct. all those wires will have full battery voltage at all times. you need to be measuring amp draw from the battery. with everything turned off you should have only a few miliamps of draw. hook the multimeter to the battery on the amp setting, and start unplugging fuses 1 by one untill you see the amp draw drop. that will let you pinpoint which circuit is actually causing the draw.

and youre right the fusable link goes to the ignition switch. its the main power feed for the cabin.

 

Thanks for the help! Ok, to measure amp draw, do I disconnect the positive battery cable, and use the MM set to amps to measure, or do I leave the cable connected? If connected, then what do I connect the probes to?

 

you can measure amp draw with the cable connected and the multimeter connected to both the positive and neg battery terms.

 

Thanks Travis,

We'll have to give that a try when my son gets home from class today.

 

I had one of the power door locks stick in, "on" and drain the battery, also had the main harness short at the spot where it passes through the firewall.

 

When mine was draining as yours is(new battery dead in a day) they told me to check the fuel pump if it was stuck in the on. in the end it ended up being the hatch motor in the back. check if the car makes funny noises when its off and keep going from there.
wish you luck finding the problem. it took me a month to find out what it was. >.<
hope it helps. -Aaron