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Discussion Starter · #1 · (Edited)
I recently purchased a 1999 9-3 and I am in the process of getting it ready for driving. I find the battery runs down to 8-10 volts while sitting in my warm garage. I had the battery checked at a local part store, and I removed the alternator and had it checked my by favourite alternator rebuild shop. Both were OK. I trust the alternator shop, but the auto parts store is questionable ..

After sitting for a week or so again in my garage I went to take it out and the battery was at around 8-volts. I put my charger on for a couple hours, brought it up to 12.5volts and it started. I ran it on the driveway for 10-minutes and the car started to stall and the lights were almost gone .. .. again the battery was back to 8-10 volts..

There isn't a volt or amp gauge on the dash, so all I can rely on is the alternator idiot light that goes off when the car is running.

I am going to pickup another battery and I could go through pulling the alternator but do I need to? I saw a note on a website about a grounding strap on the alternator... all I had was a small wire and the heavy one.. no ground straps..

Any ideas??
 

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Our alternator grounds through the alternator bracket to the engine. The heavy wire at the alternator is the positive battery cable. The smaller, yellow wire is what runs the battery indicator on the instrument panel.

The voltage measured at the battery while running or idling should be a little over 14V, same as the voltage regulator at the alternator. Even if the battery is old an will not hold a charge, while running the alternator will normally maintain it at that voltage. If the voltage is not at or above 14V, either the alternator is not charging, or the cables have a bad connection. Grounds would be an obvious place to look.

When the engine is turned off, the voltage should drop to about 12.5V, a little less if the lights are still on. If the battery is too old to hold a charge, the voltage will drop below 12V quickly with the lights and/or other things still on. Lights, car radio, cabin fan, etc. will drain a bettery that does not hold a charge very quickly.

If the alternator works, but the cables have a bad connection, then you can find out by testing the voltage at the alternator lug, and again across the battery while the engine is running. Both should be 14-14.5, with only a little difference.
 

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Discussion Starter · #3 ·
It Works Now..

well.. after having the alternator checked in the car... the alternator was defective after all.. back out it came, (I'm getting good at this now) and back to the rebuild shop.. I told him to consider it as defective.. replace everything regardless...

the rebuilder did find some poor soldering under the cover where the regulator resides.... so it looks like it was switching on and off I guess.. next replace the battery, even though it tested OK.. it is Canada in winter and boy I hate tow trucks..

thanks
 
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