View Single Post
Old 05-25-2013, 03:49 PM
upallnight upallnight is offline
Officially Welcomed to the 'Fest
Location: Crook County
Join Date: Nov 2012
Posts: 661
Mein Auto: BMW, Lotus, Porsche
Originally Posted by David Covell View Post
Ac still not working. Here's my checklist:

1. double checked ac fuses (34,48) O.K.

2. aux fan begins to spin with +12 volts across terminals. Does anyone know know which pins to check for signal to fan at the connector. With car running, don't get any voltage across any of the three pairs with ac on. Help on wiring would be great.

3. unplugged ac high pressure switch. blog suggested this should trigger compressor clutch. no effect. Alternatively, blog suggests jumping leads to engage compressor clutch. There are 3 wires black-grey, yellow-green and brown. Anyone know which to jump? Also, if this switch is bad, is there a valve at this port, as with the high and low pressure service ports, so I can remove switch w/o removing 134a.

4. wired into the circuit is a temperature switch on the low port to the radiator. Don't see how this might be a problem. Does anyonbe know how to check?
5. double checked 134a pressure. still at 115psi.

Beginning to suspect temperature sensor in passenger compartment. Sometime I could hear a slight clicking when cabin temperature close to set value. Don't know how to get to where this might be.

Thanks for any help.
The BIG 50 amp fuse behind the glove box is blown since you don't have voltage at the connector. The fuse is hot at all time. The two thick wires at the connector is + and -. The thin wire is the signal wire from the DME to pulse the fan. Only way that 50 amp fuse would blow is if the fan is bad. Even with 12 volts across the terminal the fan will not spin until it receive a ground signal from the DME. Like I said if you have a scanner that can scan the BMW HVAC modules you can verify if the fan is good or bad.

Check this post out:

Last edited by upallnight; 05-25-2013 at 04:00 PM.
Reply With Quote