Need some help with an electrical gremlin!

1999 FRC - Red Top battery is about 3 years old. Daily Driver.

For the past month the battery seems to drain overnight. But not everynight. If I start it and stop it without driving any distance I can tell its getting weaker. Eventually it won't start and all I get is a clicking - which I think is the starter solenoid.

So last week on Monday I charge the battery and she starts just fine. I drive to work and back every day. But then this weekend I started her to back her out of the garage but then an hour later she would not start.

On Friday I had Advance Auto test the battery, the alternator and perform a drain test. Everything was fine.

So now I'm thinking it has to be some sort of drain but as it's intermittent how in the world do I figure out what it is?

I've read the drain test posts on here but before I start pulling fuses - I wanted to see if anyone had any advice?

BTW I'm not getting any DIC codes.

Thanks

 

Check for draws with a test light. When I found mine, it was the glove comp light.But to pull it down overnight, it must be fairly high amp.
Did they do a load test on the battery?
I will say I have had bad luck with the optima batteries. Won't buy another. When they lose capacity, they were shot.

 

Kind of an archaic way of troubleshooting. A meter is much more efficient, and tells you exactly what the current draw is.

 

Absolutely, if you have one. But extrapolating from the OP's statement about going to autozone...
And yeah, I'm old enough to be archaic, having learned by working with very little.

 

Well, that worked fine 40 years ago, when the only thing drawing current(with the ignition off) was the clock.... Times have changed, and having the proper tools, goes along with owing a modern platform, if one wishes to effect repairs by themselves.

 

6spd or AT? 6SPD should be parked in reverse.

 

A test light works great for a large quiescent draw, but it's not going to be very helpful when testing for draws in the MA range. 20MA is typical for a C5 and anything over 50MA will cause a problem. The test light will not provide that kind of resolution.

The OP states that starting the engine, without driving the vehicle gradually kills the battery. This is normal. It takes hundreds of amps to start the engine and it takes a finite amount of driving to charge the battery back up.

I have had several folks complain that over the course of a week, or two that their battery gradually goes dead, even though there is NFF with the battery and charging system. Some of them only have a 3-mile commute, while others literally idle all the way to work and back in heavy traffic. In both cases the alternator does not have adequate opportunity to charge the battery back up. The OP doesn't mention his driving conditions, only that the car is a DD.

If your problem is truly intermittent, it could be an internal battery issue. But before spending money, I would start by checking for a draw. You don't need a fancy Fluke; a cheap $25-$30 DVOM from the local big-box home improvement store will work just fine. If you have problems reproducing the draw, you can keep yourself occupied by checking for voltage drops in the starting and charging circuits, including the various ground straps.

 

I've left my interior lights on before. Seems they are the only thing that doesn't turn off after a period of time. You can't see them in the daylight.

 

Try this, when you put the car up for the day, check the battery voltage with a voltmeter (not running). Before you start it check again. See if you are getting a significant voltage drop. You could have a drain issue. If you get something in the low 12 volt range you are getting close to the 11.7 volt range where you are going to have an issue with starting. Could be a battery issue despite having the battery tested out good.

 

I had to junk a 1 year old redtop. Went with a delco, 3+ years and going strong.