Whwn the defroster is on on my 91 Z28, the engine seems to cycle like when the A/C is on. Any Ideas???

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• 1991 Z28
• Ultra Metallic Blue
• 305 TPI
• 5 Spd Manual
• 3:08 rear axle

members.fbody.com/rwendt/

 

It is on. The car cycles the a/c on & off so it doesn't freeze up from un-use. In fact during warm months you're supposed to run the a/c every so often just to keep everything lubed up & happy.

That's why a/c occurs on the slider before "heat" and "vent" and defrost- so it kicks it in briefly.


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The defroster uses the AC compressor. The compressor de-humidifies the air blowing at the windshield. With the dry air, it attracts the moisture from the windshield.

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1989 IROC-Z 5.7L

 

If you don't want it to cycle on just unplug the a/c compressor. Plug should be on the top of it.

 

If you don't want it to cycle on just unplug the a/c compressor. Plug should be on the top of it.Although it's wise to run it every so often--just like someone said it lubes the O-rings.