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Location: Cheltenham, MD
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Volt Meter reading - what should it be?

My Volt Meter is always reading @ 12. Is that high, low, or just right. I can't find the base readout in any manual.
I had to change my battery yesterday, but first it was several years old, and secondly because I think my interior lights stayed on - the door/hatch switch to turn them off seemed to fail.
Anyone know what my meter should read?

Old 05-07-2009, 05:52 PM
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I assume you mean the meter in the dash. Mine also reads 12, but the alternator should be putting out about 14.4 when running. Needless to say I tested the car with it running and sure enough the gage in dash was reading 12v=14.2 for the car in reality.

You should test this on your car. Simply let the car idle and check the voltage at the battery with a volt meter. If it is a little low just rev it up to 2500 rpm, you will have max output from the alternator by then.

My guess is you just have a lazy gage like mine, hey for 20+ years old it can be a little lazy. Hope this helps
Old 05-07-2009, 05:59 PM
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14 is normal. You cant trust the instrument gauge though. The needle can just move wherever it wants, you can rotate it with a finger.

My dash was reading off when i tested manually. When I had the instrument panel off, I just bumped the needle a bit so now it reads 14 lol
Old 05-07-2009, 06:06 PM
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If you clean your grounds, especially those at the rear of the engine and on the bell housing, you will probably get a higher reading on your gauge. I know I did.
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Old 05-07-2009, 06:12 PM
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Ground cleaning fixed my jumping gauges. I eventually replaced all of the battery cables on the car and the voltage gauge now goes to 14v and just about everything works better now.. . Not a bad idea to make up your own cables and replace them if you have the intake manifold off.
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Old 05-07-2009, 07:37 PM
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techno duck
what did you mean exactly by everything works better?
im asking to see what is overally affected by the bad grounds. My car reads 12v now but alternative etc is OK, had all checked out by shop

thanks
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Old 06-20-2009, 01:14 PM
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upper 13's to low 14's at operating temp.

the gages are innaccurate unless calibrated.
when the case is split, there's a small calibration screw on the side of the vm.

in/out a time or to get it in sync with a decent vm.
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Last edited by bearone2; 06-21-2009 at 06:36 AM..
Old 06-21-2009, 06:33 AM
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Quote:
Originally Posted by ohio_porsche View Post
techno duck
what did you mean exactly by everything works better?
im asking to see what is overally affected by the bad grounds. My car reads 12v now but alternative etc is OK, had all checked out by shop

thanks
I used to get briefly dimming lights and bouncing gauge needles (coolant, oil pressure) when something of high electrical draw was turned on along with the headlights on. That includes rear defroster, high speed cooling fans and highest speed ventilation fan. After i replaced all the cables and cleaned all the grounds i no longer have that problem. The windows also work deceptively faster.

My car used to read right around the midway mark (13v) on the gauge. After replacing everything including the voltage regulator it goes to 14v on a cold start and will slowly work down to about 13.5v as the car warms up. I agree with bearone though that the dash voltmeter is off, in my estimates by about 1v from what you are actually putting out. Best way to check is to see what you are getting at the battery with the car running and compare it.
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1988 Granite Green 911 3.4L
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Last edited by Techno Duck; 06-21-2009 at 08:04 AM..
Old 06-21-2009, 07:58 AM
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i just got done doing my cluster swap and now everything reads what it should one mine, i cleaned all the power and grounds on the back of the cluster itself and now no more jumpy fuel gauge. it even reads completely filled up (4/4)

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Old 06-21-2009, 08:44 AM
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