I was doing some shopping yesterday, came out of the store and went to start the car and it made it two rev's then stopped, dash lights were very dim. I called Allstate road service for a jump start. The guys battery was barely able to make it turn over but it *did* start and I limped home. On the way home I was monitoring the digital voltage display on the front panel. It normally runs at 14.1v to 14.5v depending on engine speed and has always been pretty steady. On the way home it would float from 14.5 to 13.2 then somethimes change over and the "SYS" light would flash for a few seconds, then change back to the voltage display. Very weird, never seen that before.

I worked on it 'till after midnight last night trying to find the cause of the prob. I popped out ALL fuses I could find in both boxes under hood and in right hand interior fuse panel while monitoring ohms my DVM connected across the two terminals, batt disconnected, and didn't find anything definite. Looks like the 20A interior lights fuse in fuse box 2 has quite a bit of draw but I don't think that's the prob. I finally decided to hook the battery back up and monitor the voltage while pulling fuses. I still have above 12v with the doors open and underhood lights on.

I stuck the key in and turned it to "on" position and it dropped down to 8.5v then came back up to 10v after a few seconds. Wouldn't turn the motor over. I'm thinking now this might be a bad ignition switch. Anybody ever seen anything like this prob? Any guesses?

thanks
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Check out your battery terminals and all connections on alt. A poor connection at any of those locations could cause your problem.
A bad cell or loose plate in your battery could also cause your problem.

 

Yeah, I though I would try another battery from my other car just as a test. I didn't think that was the cause though b/c the battery reads 13.2v off the car. It *is* an Optima though, about 5 years old. I have no experience with how those generally fail.

Another weird symptom is the wildly fluctuating voltage readings on the dash while driving home yesterday and the intermittently flashing "sys"
message.

The schematic shows the battery only goes to 4 things, the alt, the starter and the two underhood fuse boxes. I already ruled out the alt and starter as having partial shorts inside them. Pulled every fuse while monitoring the ohms across the battery terminals and of course checked all connections for corrosion, found none...

thanks
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