aircon - fan when should it fire up?

[Overboost]

Originally Posted by PCH BMW

Today’s AC problem and the fix. AC / air conditioner / Auxiliary Fan
Mech. recommended new BMW Aux Fan ($1,000 to replace. $550 parts/ $450 2.5 hours); and return in 1 week to visually inspect for leaks (look for dye with a special light ).
Outcome: I will likely replace the AUX fan myself once I zero in on a non-BMW brand fan that costs less than a new set of golf irons.

When I replaced mine I got a new Behr unit off fleaBay for under $200. You have to pull the front bumper but it honestly takes about 1 hour start to finish.

[PCH BMW]

Thanks for the info Overboost.

[Blackjetvette97]

Hi all,
So, my compressor clutch IS engaging. Tested low side pressure as I watched the clutch engage(pressure began at 100ish). Clutch engaged and pressure didn't hardly move at all. Fan does not turn on at start-up for test run or when A/C is on Max. There was NO cool air blowing out, even with comp clutch engaged. I assume, since pressure is so high on low side, that it indicates no leak(would there be low to no pressure if leak?).

[80stech]

That pretty much points to a bad compressor.