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Should A/C compressor engage for heat?

Old 04-01-2018, 07:44 PM
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Default 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. Didnít think this is right, but I donít 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.
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Old 04-01-2018, 08:26 PM
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The compressor should come on in any of the defrost modes.
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Old 04-02-2018, 07:15 AM
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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.
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Old 04-02-2018, 08:59 AM
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Thanks Dave! No it doesnít make sense, but I get it. Had a 99í 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
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