Question about 2000 Jeep Grand Cherokee

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Voltage gauge periodically drops from 14 volts to 9 volts every couple of minutes and then it will go back up after you turn the heat off, with no other changes to lights or the engine. Also the tempature gauge starts rising after about 20 minutes of the truck running. Is this the altenator and maybe a theromostat?

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I had this happening on my 2004 GC and it was the alternator brush block worn to limits. You can get a new brush block, or a complete new alternator. There is also a good change that your battery is going bad due to the alternator. 9V only indicates a dead battery cell.
Does the engine temperature rise while driving, or when standing still only? In the first case, I would first expect the thermostat, in the second case the cooling fan is most probably not working.

Posted on Dec 16, 2017


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I believe you have two separate problems sounds like an alternator possibly going bad regular inside it internal, and you may have electric cooling fan not coming or bad fan or sensor or possibly plugged up radiator

Posted on Dec 10, 2017


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I would say the alternator. The fluctuations when it is running indicate that the regulator inside the alternator is worn out. The overheating is probably because the cooling fan is not running fast enough or at all.

Posted on Dec 10, 2017

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Posted on Jan 02, 2017


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SOURCE: Voltage Gauge drops suddenly to zero

Charging system grounding out, poss inside alternator

Posted on Jan 31, 2009


Harvey N Tawatao

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SOURCE: Oil pressure gauge drops after running and sitting still

The Oil pressure sensor seams to have gone bad and needs to be replaced soon as possible as they tend to leak oil soon after. There common to go bad and start with that since it's easier then replacing the oil pump, but if you don't hear any ticking from the engine and you have good pressure when the engine is cold then it's the sensor. 
The 4 cylinder oil pressure switch is located below the A/C compressor. It is a single wire connection with a gray/yellow striped wire. 

The 6 cylinder oil pressure switch is located on the passenger side rear of the block. It is a single wire connection with a gray/yellow striped wire. 

Good luck and hope this helps. 

Posted on Jul 01, 2009


Clint Smock

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SOURCE: Tempature Gauge High

Check the cooling fan.

Posted on Jul 05, 2009


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SOURCE: voltage gauge drops below 14 volts when vehicle

have your battery tested perform a Load test it has to hold at least 12.4 volts to be excelent,you can get away with 11.8 or 11.9 and it will still be good,any lower replace it.
also on a jeep 13.2 and up is okay,with everything on.
Any lower than that you have a problem in your wires.Check at the alternator,if iot looks good then you need more help.

Posted on Aug 10, 2009

Richard Scordino

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SOURCE: check engine light flashes and engine stalls at

Make sure that your battery cable contacts are clean and secure at both ends including any body grounds especially at both fenders, firewall and dashboard lower brace. If all is good, likely your alternator is failing. Be aware: some of those charging systems have the voltage regulator as an integral part of the computer, not in the alternator. If you find that the alternator checks out and the wiring for it is intact and its connections are clean, there is a possibility that the regulator has failed. If so, the computer needs to be changed. You don't necessarily need to get a new one as most are available much cheaper in a scrapyard (Id get one that was in an accident...ones with perfectly good bodies may have had engine problems otherwise they would still be on the road!

Posted on Nov 17, 2009

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