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kgorczyn 01-22-2013 10:19 AM

AC Will Not Engage
So my HVAC system has been acting 'funny' last few months. Sometimes when I start the car it doesn't work (it turns on and looks ok, but changing the fan speed, vents, temp, etc. does not work - it shows the changes on the LCD but does not apply them) - I turn off and on the car and then it's fine again.

Now however, I have a different problem that a restart will not fix.

HVAC Unit turns on fine, I can regulate the temp, all functions work, except the AC. When I press the AC button it turns green, but compressor does not engage, RPMs do not kick up. It's like it isn't doing anything.

Any ideas on what this can be? I reseated all the HVAC connections on the back of the unit, it did not help. I also disconnected the battery for 15+ minutes, did not help.

DHoang 01-22-2013 11:22 AM

YOu may have a refrig leak.
THE A/C system needs a minimum amount of refrig pressure in order to
activate the clutch on the compressor. WIth a leak, your system pressure drops
too low to have the compressor working properly.

Nervous 01-22-2013 11:24 AM

Oh, man. This is a loooong story. Too many variables. I had a similar issue on my e46 and created this topic:

Even though it is for e46, most of the info is still relevant to e39.

Start with checking pressure in high and low ports using DECENT gauges. DO NOT ADD ANY FREON FROM EASY-TO-SCREW-UP-YOUR-COMPRESSOR kits from Walmart / Autozone / Advance / etc!

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