Should A/C compressor engage for heat?

Reply Subscribe

Thread Tools

Search this Thread

04-01-2018, 07:44 PM

Peter1969

Newbie

Thread Starter

Join Date: Mar 2018

Location: Daphne, AL

Posts: 25

Likes: 0

Received 0 Likes on 0 Posts

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; 04-01-2018 at 07:52 PM.

Reply Like

04-01-2018, 08:26 PM

00t444e

CF Veteran

Join Date: Nov 2015

Location: Southern OH

Posts: 3,604

Likes: 2

Received 456 Likes on 369 Posts

Year: 1997

Model: Cherokee(XJ)

Engine: 4.0

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

Reply Like

04-02-2018, 07:15 AM

dave1123

Old fart with a wrench

Join Date: Nov 2010

Location: Manlius, east of Syracuse, NY

Posts: 14,398

Likes: 14

Received 723 Likes on 628 Posts

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.

Reply Like

04-02-2018, 08:59 AM

Peter1969

Newbie

Thread Starter

Join Date: Mar 2018

Location: Daphne, AL

Posts: 25

Likes: 0

Received 0 Likes on 0 Posts

Year: 2000

Model: Grand Cherokee(WJ)

Engine: 4.7 V8

Thanks Dave! No it doesn’t make sense, but I get it. Had a 99’ Taurus and usually left it on auto, even changed the compressor on it. No telling how many mpg was lost to it coming on. Though in lower Alabama the heat function is hardly used. Thanks again! Get to check off the A/C as repaired and ready for the hot weather

Reply Like