I’m having a voltage/voltmeter problem.

If I start the car and the car is cold, I don’t have any reading on the voltmeter whatsoever. After running for 15 – 20 minutes, the needle on the voltmeter starts to move reaching about 13 volts after 30 minutes or so.

If I start the car and the car is hot, the voltmeter immediately reads about 13 volts.

If I start the car and the car is cold, but it’s been sitting in the sun on a warm day, the voltmeter immediately reads about 13 volts.

I’ve never really had a starting problem, but the car is usually on a battery tender since I don’t drive it that often. Any idea on what it could be or how to test the charging system?

Sam

 

ck with a good digital meter in all the same conditions.

take it to checker, autozone, napa,, etc, they'll ck the electrical system for free in the car.

87951

 

The only way to get an accurate reading is to start the car, disconnect the batter + terminal and 1. check voltage on the terminal (should be 13.2-14v) then 2. check battery voltage disconnected for a day or two. If the battery is good, it will be the same reading and be over 12v. If it has a short in it, it will show less reading after a couple days. (or do as suggested and take it somewhere)
Check with a digital meter though.

 

start the car then disconnect the + batt terminal to ck voltage, i don't think so.

what you're describing is to see where you have a batt draw that's above normal but the car isn't running.

87951

 

by disconnecting the battery with the car on, and checking the voltage on the cable (not the battery end) you'll find out the charging voltage without the battery loading it down. If the battery is internally shorted, the charging voltage will be down. I didn't make that too clear. CABLE, NOT BATTERY TERMINAL.

 

Thanks, I'll give that a try. If it doesn't work out, I'll be off to autozone or napa.

Could it be a bad ground on the gage? I've read a lot about electrical gremlins being caused by bad grounds.

 

If all is well with battery & alternator

Check the leads to the voltmeter, They could need some tightening

IE: Cold metal shrinks, warm metal expands

 

Everything I have ever read warns not to disconnect the battery with a car running. I think it's because the voltage can increase to dangerous levels at higher RPM since the battery load isn't there. I have done it at idle to see if the alternator was working on other cars with no problems though.

 

You are correct. As you increase the RPM, the regulation circuit can fly sky high. Not a good thing. At idle, it should be very close to charging level without a load. It is not at charging level with the battery loading the circuit at idle.
Also, I agree that it may be something as silly as the meter or leads of the meter. I've run into dumb things like that before.

 

Do that to your old chevy, not your porsche

 

Does anyone have a link for the instrument cluster removal? I checked on Clark's Garage. It says to remove the steering wheel, but doesn't have a good procedure for a late model wheel w/ airbag.

 

I just consulted Haynes on that, and it says "WARNING: if equipped with air bag, have Porsche dealer disarm and remove prior to removing the steering wheel."

So I wonder if it's just a question of disconnecting the airbag, then just following the same steps as usual? Not something I'd wanna be wrong on, though.

 

I have a 90 944S2 cab and removed the instrument panel just the other day. Very easy 30-45 minutes. The problem you encounter is that when you disconnect the air bag the warning lights will be activated ie Air bag light, central warning light and seat belt light. The only way to clear these lights is via the dealership or someone with a Bosch hammer. The dealership cleared mine for $30.00. If you still want to do it I can give you step by step instructions.

 

I just got it back from Holbert's Porsche. The charging system checked out fine. Seems I have a "slow" gage. They suggested I leave it alone. I think I agree.