Cameron38

iTrader: (2)

On my 85 SE, if the car sits for a week, the Battery will be dead. Replaced the old battery (of unknown age) with a brand new one. Same thing. The Alternator appears to be working fine. Charges the battery right up once it's been jumped. Must be a battery drain somewhere that takes about a week of sitting to drain the battery. Any ideas where to check? Electrical is my weakest automotive skill.

turbogslse

iTrader: (3)

Have you replaced the alternator lately? There are two alternator types, one with an internal diode, one without the diode. IIRC, the diode prevents slow drain through the alternator wiring.

The other thing to ask is whether you've done any work recently on the car that may have disturbed any wiring?

alfajeffrey

iTrader: (7)

My 82 started having issues that were intermittent. I had a brand new battery, alternator, and most ignition components.

After running several tests. I found out my alternator was only putting out 12.5 volts on average.

Turned out my 5 month old alternator was the culprit. Had it swapped under warranty, and now it runs great.

The bad alternator caused lots of strange symptoms. Main issue was the loss of my trailing coil (and tachometer). Since it was putting out 12.5 volts, the problem appeared to be more likely an ignition issue.

Cold weather and moist air made the issue intensify, and prevent it from starting at all.

Hopefully that is your only issue. I also cleaned all connections from the battery all the way to the spark plugs. I also checked all vac lines at the same time.

She is running great now!

KansasCityREPU

iTrader: (9)

It's easy to take your alternator to the parts store and have it tested.

The other option, which would be a pain, would be to disconnect the alternator when you park it. If the problem goes away, it's the alternator draining the battery when parked.

Cameron38

iTrader: (2)

How many volts should the alternator be putting out? I assume using the dash gauge is more or less useless.

dougingraham

This isn't the right question. The output voltage of an alternator (or generator) varies with the RPM. The regulator controls the alternator field to adjust the current which is in turn adjusted so the battery voltage comes out where they want it to be. It is a pretty simple feedback loop.

Any decent battery shop can hook a tester to your battery and do a test specific to discovering if the battery/charging system is good. It does this by placing a load on the system with the engine running and seeing how the charging system responds. The good ones can tell you how many amps the charging system can generate. I think I paid $8 the last time I had this done.

Typically the voltage seen at the battery while the engine is running should be between 13.8 and 14.4 when the battery is fully charged.

I would look for a stuck switch that leaves a lamp on. Like in the glove or storage boxes or the hatch glass open lamp. Any of those left on will drain the battery in a few days. Normally the only load on the battery with the key off is the clock and circuit that maintains the radio presets. If you have an after factory stereo I would look to make sure the power amps are getting turned off.

lwrobins

Check for a quiescent draw or parasitic drain. Must have a DVOM, but easy to do. just look it up...

Cameron38

iTrader: (2)

Thanks guys, it's going to my favorite mechanic Thursday for an A/C system upgrade, so I'll have him check the Battery and Alternator while he's at it. The car does have an aftermarket stereo. I'll remove the storage bins and make sure the old Amps are disconnected.

Cameron38

iTrader: (2)

Update: The Old Amps where still connected so I disconnected them just in case they were drawing any power.