Should A/C compressor engage for heat?

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Apr 1, 2018 | 07:44 PM

Peter1969

Thread Starter

Newbie

Joined: Mar 2018

Posts: 25

Likes: 0

From: Daphne, AL

Year: 2000

Model: Grand Cherokee(WJ)

Engine: 4.7 V8

Should A/C compressor engage for heat?

2000 gc. Just replaced accumulator with hoses, then had it evac/press tested and charged at mechanics. Noticed the compressor kicks on for heating. Didn’t think this is right, but I don’t fully understand the chemistry involved with hvac. Did note that if air selector is set to floor only the compressor goes off when heating. If left on auto or the other settings and heating the compressor comes on. Stumped/scratching head. Lol Any answers would be greatly appreciated, as the ole dog needs to put this as a completed fix. Happy Easter!!

Last edited by Peter1969; Apr 1, 2018 at 07:52 PM.

Apr 1, 2018 | 08:26 PM

00t444e

CF Veteran

Joined: Nov 2015

Posts: 3,636

Likes: 469

From: Southern OH

Year: 1997

Model: Cherokee(XJ)

Engine: 4.0

The compressor should come on in any of the defrost modes.

Apr 2, 2018 | 07:15 AM

dave1123

Old fart with a wrench

Joined: Nov 2010

Posts: 14,398

Likes: 740

From: Manlius, east of Syracuse, NY

Year: 2000 XJ Sport & WJ Laredo

Model: Grand Cherokee (WJ)

Engine: 4.0L

There's really no need for it to come on, but it does. When A/C first was installed in cars, people never used it all winter, as expected. Without cycling, the seals dry up and the freon leaks out so it had to be recharged every spring. Auto manufacturers decided to have the compressor cycle every time you used defrost to eliminate this problem.

Apr 2, 2018 | 08:59 AM