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A/C help

Old May 17th, 2019, 7:43 PM
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Default A/C help

AC compressor runs on first 3 [ac] settings,off on next 2 [face and foot], and then on again for last 2 [window] settings. Is this normal? Why I ask, if I run HOT air onto window for defrost in winter, the compressor runs too. The compressor bearing went out, so I couldn't defrost windows till I had it replaced. Just seems weird, ac running with HOT air.
2004, Express 2500 V8 6L. 350,000M.


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Old May 17th, 2019, 8:57 PM
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normal. air that runs through the air conditioner will help prevent window fog up; less moisture... hence why it run only on the 2 defrost setting in winter. The ac won't run for long at cold temps to prevent evaporator freeze up
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Old May 17th, 2019, 9:19 PM
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Hey Tech, I thought it only ran on the last one, full defrost. Not the defrost floor combo one. Is it not also to lubricate the system by running the compressor a few times in the winter instead of it not running for months on end?
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Old May 17th, 2019, 10:17 PM
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I thought it was both but you may be right. and yes, that is another reason for it to run.
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Old May 18th, 2019, 5:46 PM
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Next question. The a/c runs for 15-30 minutes, with the air flow slowly getting weaker and weaker. Eventually stopping altogether. Turn off, and it slowly comes back. Is this the coil freezing over?
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Old May 18th, 2019, 10:27 PM
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air flow or air temperature?
if it goes warm...it could be a tired compressor or low charge. to test this...when it goes warm...rev and hold the engine rpm at 2500rpm....if it goes cold again. check the charge level; if charge is ok...replace the compressor.
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Old May 19th, 2019, 5:45 AM
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Air FLOW. Eventually no air coming out the vents. Turn a/c off, and it comes back slowly to full strength.
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Old May 19th, 2019, 9:11 AM
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does it does this on hvac functions with the a/c not engaged.
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Old May 20th, 2019, 5:51 AM
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Originally Posted by tech2 View Post
does it does this on hvac functions with the a/c not engaged.
Van driving, a/c working. Airflow slowly dissapears, on first 3 settings on dial pic above, and last 2 [6 and 7]. Airflow slowly comes back to full strength on 4, 5, and off.

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Old May 20th, 2019, 7:52 AM
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if you think it is evaporator freezing, remove the compressor fuse/relay and see it the problem goes away. if the problem is still there. I would check the wiring at the blower switch and resistor.
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