Syncman

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.

tech2

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

canucklehead

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?

tech2

I thought it was both but you may be right. and yes, that is another reason for it to run.

Syncman

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?

tech2

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.

Syncman

Air FLOW. Eventually no air coming out the vents. Turn a/c off, and it comes back slowly to full strength.

tech2

does it does this on hvac functions with the a/c not engaged.

Syncman

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.

tech2

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.