RPM Flux

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06-19-2009, 09:54 AM

RICZR2

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Year: 2001

Model: Cherokee

Engine: 4.0

RPM Flux

Had my 2000 XJ about a week now and I noticed today that when I have the selector **** in the Defroster/Defogger position, the RPM fluxuates. About every 5 seconds the RPM raises .....then drops back to normal. The rise is about 100 to 200 RPM. It's very noticable at idle but you can tell it's doing the same thing as your driving at low RPM also. I noticed that it sounds as if the Air Conditioner compressor is cycling on and off. NOTE: the air conditioner is not on.

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06-19-2009, 11:02 AM

TimSTL

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Model: Cherokee

When the defroster is running, the A/C cycles to pull out moisture.

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06-19-2009, 11:08 AM

89Laredo

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Year: 1996

Engine: 4.0

Quote:

Originally Posted by TimSTL

When the defroster is running, the A/C cycles to pull out moisture.

Yes, the air conditioning switches on and off to take out moisture, the rise in rpms is because of the extra strain the compressor puts on the engine....