New FSU now blows hot air,help!
 

I just change the FSU last night done it before,it worked great last night.Today the AC stop working, first it blows hot air to your feet.No cold air thru the top outlets and the air cond. control panel does not work or light up is totally dead,also when you turn off the ignition switch,the air cond. blower stays on,with the key off the ignition,I unplug the FSU plug and it stops,but as soon as I presented to FSU the blower turns on.Checked fuses all ok. I want to know how can the blower keep running with the key off the ignition and no power at the control panel? .Can anyone help telling me whats wrong now with the AC system?Thanks.

The final stage unit only controls the fan speed output, so wouldn't cause the problems you are experiencing. Sounds like you have a blown fuse for the AC system control panel... Look at the AC fuses in the glovebox and you should find the blown one.

I just checked all fuses and they are ok.I'm stuck now don't know what else to do.If you have any suggestions let me know,thanks,Rafael.When you mean AC system control panel,what do you mean exactly.I looked at the fuse box and check ac fuse and everything else that has to do with the system,they were all good.

There is a heater diverter valve, you can see pics of them on Auto Parts at AutohausAZ - OEM Auto Parts - Discount Replacement Parts, Resources and Car Care Tips or Google 'BMW heater valve'. Its near/on the drivers side shocktower. These commonly fail due to lack or regular coolant flushes.

When the ihka control panel is disconnected with the ignition on. With some newer cars the blower continues to operate.

If all the fuses are good, the ac control, known in BMW terms as the IHKA, likely failed... And without it to translate all the input/output signals the ac will not work right.

Getting the panel off and finding the FSu literally took me 5 minutes..but I've been battling for 30 minutes trying to get the plug off. My fingers hurt from so much squeezing the clips on the harnes.. Wanted to use pliers but i'm afraid i may break the clips on the harness. Any ideas?

Squeezing the clips isn't the hard part, it's pulling the plug loose once the clips are squeezed. The pins in the plug can have a pretty good hold of eachother. I sometimes remove the FSR from te housing with it still plugged in just so I can get my hand around it to pull.

^^^Hey weasel, what happen if it was the other way around? I'm getting cold A/C, but no heat.

The FSR has nothing to do with the temperature of the air, just controls the fan speed. If it blows cold but not hot it is more than likely the heater control valves. If you want to confirm that diagnosis yourself pick up one of those infrared thermometers with laser pointer you can see what hoses get hot and where the heat stops in route to the heater core. But as I said, likely the heater valves.