Actually, my passenger side vent doesn't blow (very well), and that's the problem. Vehicle: 2001 540i, 110k miles, all services up to date. Symptoms: Flow of air from passenger side vents only is very low; driver's side vents have good flow. Increasing the fan speed does not seem to have any effect. Closing driver side vents does not seem to improve flow on passenger side significantly. Also, problem does not appear to be affected whether the AC is on or not. The flow on the passenger side is just low all of the time. Question: Does this sound like the Final Stage Unit has failed or just a clogged pollen filter on the passenger side or something else? Thanks for any feedback/suggestions.
Do you have any way to scan the climate control unit? Did you look and the filter under the hood, and check to see if there was any blockage in the tube going into the car?
I don't have a scanner to check the climate control. The only scanner I have is the Peak unit for system codes. I can check with the indie BMW shop I use and have them scan the climate control unit. I will double-check the tubes/ducts going into the car. I didn't see any obvious clogs in the ducts when I checked the filters yesterday, but I'll check them again. I was reading about the climate control unit in my Bentley's manual and I see that there are a series of "stepper motors" that hang off of the control unit. Do you know if failure of those stepper motors is common? Are the symptoms with my system consistent with the failure of one of these stepper motors? I guess the scan of the climate control will tell me if it is a stepper motor. And I assume that since the driver's side is working correctly (strong air flow and flow adjusting up/down with fan speed), my problem is not the blower motor, correct? I was really hoping it would be the FSU that is discussed all over the BMW websites. Faulty FSUs are apparently pretty common on the E39s (and pretty easy to access and swap out), but perhaps not indicated by the symptoms I am experiencing with my car.
It's not the FSU, or the blower, due to having strong flow out of the drivers side. Those stepper motors do fail time to time. Scanning it will tell you if you have a fault with one of them. Other then that, it's rip and tear to get to them to check them indivdualy.
Got it. To get to the stepper motors it looks like I need to pull the climate control unit. And to pull the climate control unit, it looks like I go throught the front of the dash (remove the MID then the climate unit). But it does not look like I need to take apart the whole dash (like if I had to replace the blower motor). Correct? Thanks for your help.
Correct. You do not need to pull the whole dash apart to get to them. You may also want to take down the glovebox to give yourself a little more room. Good luck. No problem. Anything else, just give a shout.
