HVAC prbs

My HVAC controls (the green lights in all 4 circles don't light up, so there is no function at all) would not work about 10% of the time I start up the car. So the dealer diagnosed the prb and supposedly it was a faulty control unit, which was subsequently replaced. However, the prb still occurs: not sure if you guys have any ideas what it could be? It is very weird because it still works but sometimes it doesn't.

Hi! when all of the lights are off have you tried to switch the blower on for example? It could be a faulty relay or a loose fuse as it appears to be a power issue!!!! even though the control unit has been replaced.

Originally Posted by 645/333

Hi! when all of the lights are off have you tried to switch the blower on for example? It could be a faulty relay or a loose fuse as it appears to be a power issue!!!! even though the control unit has been replaced.

I have tried pressing all the buttons but none of them work when my HVAC is acting up; when it works, it is fine, all functions go. I'm not technically-inclined, but I agree w/ your assessment...it must be sometime loose or a software glitch because my HVAC works most of the time.

bump.
Well, the rear defroster button still works even when the rest of the buttons don't whenever the HVAC acts up.

given your car should still be under warranty, you should just take it back to BMW!! I did have a look on a Wiring diagram but it is only for the E85 Z4, 2007 just to see if anything was obvious, sadly I could not see anything.......

^Yup, I definitely will take it back. They seem to have missed the prb so hoping you guys could provide the answer.

For those that did the 'master reset' aka 'touching battery cables together', how long have you been prb-free? Any side effects? Thx.

Originally Posted by tranquility

For those that did the 'master reset' aka 'touching battery cables together', how long have you been prb-free? Any side effects? Thx.

Didn't have this problem during ED. After dealer replaced iDrive control module and reprogrammed, I noticed this issue. Dealer did 'master reset'. But I am noticing this issue frequently. I am taking in the car today for the infamous 'Engine Malfunction, Reduced Power' issue. I will have them recheck the AC issue.

Originally Posted by cuddapah

Didn't have this problem during ED. After dealer replaced iDrive control module and reprogrammed, I noticed this issue. Dealer did 'master reset'. But I am noticing this issue frequently. I am taking in the car today for the infamous 'Engine Malfunction, Reduced Power' issue. I will have them recheck the AC issue.

Darn, so you had the 'master reset' procedure done and you still have this HVAC prb? Pls keep us posted on any possible solution(s). Good luck on a fix. I still have this prb sporadically also.