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slightly higher idle RPM with front defrost?
Posted: Sat Nov 11, 2017 5:13 pm
by salinity
I noticed something over the past couple days - if I'm idling with the fan on in either front defrost or front defrost/floor selected I idle slightly higher (based on RPMs) than if I select vent or vent/floor. Does this make any sense to anyone? I assumed it was just a blend door that changes with the vent selection. I noticed this because I get an audible "chirp" at 800 RPM, but not 850-900 and the little uptick with the front defrost selected makes that difference.
Re: slightly higher idle RPM with front defrost?
Posted: Sat Nov 11, 2017 8:46 pm
by andrewclaus
Front defrost always turns on the A/C, which often requires a higher idle speed for the extra compressor load.
Re: slightly higher idle RPM with front defrost?
Posted: Sun Nov 12, 2017 2:51 pm
by salinity
andrewclaus wrote:Front defrost always turns on the A/C, which often requires a higher idle speed for the extra compressor load.
Interesting - thanks for that info. My Cherokee doesn't have AC, so I've apparently been out of the loop for the last 12 years as far as the apparently common AC-assisted front defrost. I did notice the extra load (headlights dim slightly, etc) when turning the front defrost on last night.
Re: slightly higher idle RPM with front defrost?
Posted: Tue Nov 14, 2017 4:24 pm
by SeattleJeremy
Yep, this is totally normal.