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Mcfleev-O
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DEC 12, 05:22 PM
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Been experiencing an odd electrical issue with my 1999 Jeep cherokee. Before I start the Jeep on a cold day the voltmeter in the gauge cluster reads 12 volts. Good, right where it should be. When I start the engine the voltmeter remains at 12 volts as if the alternator was not running. Moments later the voltmeter drops to 9 volts (where the pin for the needle is at so really 0 volts). I immediately grab my DMM and test the battery...14.5 volts with the vehicle running. I check the connection on the alternator to assure it was in fact charging the battery and again right where its suppose to be. (12.8 volts off and 14.5 running) I let the Jeep sit overnight to test the battery cold in fact ran it up to AutoZone to load test it and check the charge. 100% passed. I put the battery back in with new terminals and ground wires, you know the big 3 (even added a couple more grounds just to be safe) Started the Jeep up and success! 14 volts in dash shown.
fast forward to this week and I experience a similar issue. after starting the engine cold, my dash reads 12 volts for about 3 minutes then will jump to 14 volts. It wasn't until today that my volts dropped to zero again...Back to the drawing board.
While it was still reading 0 volts I drive the Jeep to Car Quest and had them test my electrical system while it was running. 14.6 volts 100% on battery and alternator.
After some good thought I begin to suspect the voltage regulator causing these odd issues however on 97 and up Jeep cherokees; the PCM regulates voltage so not really something I can test...easily that is. I checked the Jeeps schematic routing the PCM and the dash components to find that the 16 pin PCM scanner connection has powering wire that should be running through the voltage regulator (theoretically) I did get exactly 12.0 volts on this connection, mind you that the Jeep was behaving when I tested this. turning on some accessories like the window defroster to see if I could trigger something and again 12 volts. so what gives?
I'm out of ideas so please feel free to chip in with some expertise[This message has been edited by Mcfleev-O (edited 12-12-2014).]
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tebailey
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DEC 12, 08:09 PM
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2tone86gt
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JAN 06, 01:13 AM
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I second that. If the regulator was bad you would not be putting a charge back in the battery. 13-14 volts running is right on the money. Any good battery while it is off should be between 12-13 volts however it all comes down to CCA's when knowing a battery is still good voltage can be misleading. With the amount of junkyards out there it shouldn't be to hard to find a Cherokee with a good cluster. Or you could get a aftermarket guage at Advance or pep or whoever and hook one up easy.
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Raydar
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JAN 18, 11:22 PM
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Check grounds between the cluster and... everything.
We had a 98 Wrangler that, occasionally, all the gauges would drop to zero. Hitting a bump caused them to resume normal operation.
It happened so infrequently that we never even bothered with it.
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