94 JGC - Low Voltage reading

[rspydir]

My 94 I6 has been showing low voltage (9.5-10) on the guage on the instrument panel. It's a new battery (april '04). I had the alternator checked twice at different places and it's OK. Serpentine belt was worn, so I replaced it.

I cleaned the battery terminals, the ground connection from the battery to the body, and the ground from the battery to the engine block, just under the distributor. That seemed to do it. Voltage at 13.5 or so for about 40 miles...then back to low voltage.

Popped the battery cables, then replaced w/o cleaning anything and the voltage goes back to 13.5....then slowly drops...

Is there another grounding strap somewhere? I checked all around both sides of engine, under the engine, behind the engine, around the transmission...can't find one.

Has anyone else experienced this type of behavior or know where I should look next?

thanks

[JDPascal]

How slowly does the voltage drop after you reconnect the battery cable??

If you have a set of jumper cables - connect one black jumper clamp to the battery neg. terminal and the other black clamp to the alternator mount.

Make sure that you have good contact and then watch what the voltage does.

If the condition is the same as before, I'd say the grounds are OK.

JD

[JDPascal]

Do you have a digital volt meter??

JD

[Dale Aeppli]

Originally Posted by rspydir

My 94 I6 has been showing low voltage (9.5-10) on the guage on the instrument panel. It's a new battery (april '04). I had the alternator checked twice at different places and it's OK. Serpentine belt was worn, so I replaced it.

I cleaned the battery terminals, the ground connection from the battery to the body, and the ground from the battery to the engine block, just under the distributor. That seemed to do it. Voltage at 13.5 or so for about 40 miles...then back to low voltage.

Popped the battery cables, then replaced w/o cleaning anything and the voltage goes back to 13.5....then slowly drops...

Is there another grounding strap somewhere? I checked all around both sides of engine, under the engine, behind the engine, around the transmission...can't find one.

Has anyone else experienced this type of behavior or know where I should look next?

thanks

HI, CHECK THE TERMINAL ENDS ON GROUND CABLE AND THE ONE SMALL WIRE THAT GOES FROM GROUND CABLE ON BATTERY TO BODY THIS IS JUST A SHORT WIRE HAVE TENDENCY TO BREAK INSIDE CAN'T SEE WITH OUT REMOVING, POSSIBLE CORROSION INSIDE CABLES CAUSING VOLTAGE LEAK DOWN. REPLACE CABLES WITH NEW ONES HOPE THIS IS OF HELP DALE [email protected]

[rspydir]

Originally Posted by JDPascal

Do you have a digital volt meter??

JD

Yes, I have a digital voltmeter

[JDPascal]

Originally Posted by rspydir

Yes, I have a digital voltmeter

rspydir

What did you find with what Dale described above??

That is a good possibility.


You can check the ground connection with a digital volt meter by switching the dial on to a setting higher than 12 volts and placing one of the probes on the negative battery terminal and the other probe on the frame/body at the connection. Make sure you have good contact with the probe.

Ignore the polarity indicator if any and read the voltage. The smaller the number the better but no more than 100mv on the ground side. If the voltage reading is less than the next lower voltage scale, switch to it for a more accurate reading.

http://www.fluke.com/application_not...1&SID=103#volt

The link above shows the method. Current must be flowing so if it is the charging circuit, the engine is running; if the starting circuit, the engine is cranking; a light circuit, the light is switched on etc.

You can locate a problem in a wire or circuit right down to the exact point where the contact is broken or the resistance is located.

I usually start by doing a total circuit test. For the hot side of the charging circuit, one probe would be on the positive post at the battery (not the clamp) and the other on the threaded stud at the alternator. With this connection, you can wiggle wires and see if the voltage reading changes. Then I move ONE probe closer to the other.

Keep moving that probe untill you see a change in the reading then put them on the connections closest to either side of where the problem appears to be to double check.

Let us know what you found so others can benifit from your experince too.

JD