I was reading through some posts and decided to do a test on my own. I've got a new Bosch battery in my car (maybe a couple months old) and when I strap my Fluke across I get a nice 12.7v. When I start the car and let it run to idle the voltage jumps to about 13.5. It doesn't change much, if any at all, when I load the system - turn on headlights, heater, etc... maybe .1v if anything. My dash gauge seems right on as well - matches up with what the Fluke is telling me.

I read some other posts that 'normal' is around 14.3v once the car is running across the battery.

I don't seem to have any squirrely electrical issues and I know that upgrading all my +/- cables would help - but are these numbers within spec or do I need to start looking closer at some other stuff?

 

I'm currently running on 12.05V lol... I have a problem.
You are above 13V, so I would say you're doing fine.

 

Quick update...went out and tested again after the car was really warm. I've cleaned up all my grounds but I think it's either a old wire issue or possibly alternator/voltage regulator.

When the car is really warm the V across the battery is about 13.3V. If I turn the lights on which I know is a big draw (I think ~20amps), the voltage immediately drops to 13.1. The dash gauge is pretty much right on with what I see on the Fluke MM.

I also notice that my AFR's as the car gets really warm on the wideband slowly moves off 14.7 where it parks from the time the car starts up down to the high 12's low 13's. When the car is really warm, turning the lights on and off for example has an immediate impact on the AFR's.

Is this the classic battery cables are gunged up, too much resistance and as they heat up they start eating voltage or something else?

 

a battery is fine between 12.45V(75% of charge) and 14.25V, max point. if anything you have a good setup with good wires and battery. even with full loads on a battery, it shouldn't drop much, they're designed to function with everything turned on.

 

Thanks. I'm sure there's probably worse off cars than mine - but I want to get it right and have inspection coming up in a few months and not sure I can pass once the car gets warm and starts idling in the high 12's.

It seems like it has something to do with heat as a cold start comes right up to 14.7 and then after the car is fully warm the AFR on the wideband slowly start ticking down. They never really go belwo 12.5 or so and can fluctuate from there to the mid 13's - either way, still to rich to pass inspection I would think.

That said, even with the fluctuations, the car idles great. I had it hooked up to the PB tonight and it stays right in the 840 +/- 20 RPM's all the time but strangely even with the PB was unable to dial in enough negative fuel to get the AFR at idle to come back up. I could dump fuel in and get it to choke but could back it out as far as it would go and the AFR never would come back into the 14's.

 

i see just above 14 after starting and just a little below 14 when warmed up, lights, a/c and radio on and my gage is calibrated to a fluke meter with the set screw on the side of the gage in the cluster.

87951
95sl320 dd