Thread: AC DIY in 540i?
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Old 05-25-2009, 04:31 PM   #11
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Join Date: Aug 2007
Location: down by the river
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Originally Posted by daveyto View Post
Does anyone have a DIY for AC in a 540i? 2003
I don't have a DIY, but I can tell you how I fixed my AC..

Compressor clutch was not kicking in and aux fan was not spinning.

Low pressure port with compressor not running was ~80 psi. (pressure is very dependent on ambient temp) This told me my system does not have a leak, and the R-134a level is good.

On my car, 2001 530 (MS43) the DME tests the aux fan to make sure it spins. If it fails the test, it set a code (125) in the DME. This is not an OBD code, and a generic OBD reader will not see it. I used carsoft.

My Aux fan shorted out right at the fan motor, melted all the insulation on the wires, and popped Fuse 75 (50A).

Replace fan ($375), replaced 50A fuse ($3), and reset the DME error memory.
A/C is now working great.
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