Automatic climate control

My 2005 BMW X5 3.0d is a recent purchase after owning a BMW 630i Sport and is the seventh BMW I’ve owned. I do all my own servicing based on knowledge gained from reading CM.

My problem concerns the automatic climate control. I always run the system in auto mode, but I need to select auto each time I start the car, as after full shut down and sleep mode, it defaults to the screen clear setting. The blower seems to be in auto mode and all functions work as intended, it’s just the memory from where it was left that it forgets. The other fault is with the blower function, which can be reduced to its lowest setting and switched off by one further press, but which switches back on again on releasing the button when it should stay switched off.

BBA Reman has said it will look at it and, if it's repairable, would charge about £108, but I could buy a secondhand one for less on ebay. My main concern with fitting a used unit is that the BMW repair manual says a replacement AC panel would need coding to the car. Given the technology is from the E38/39 era, surely obtaining a unit of the same part number would be just plug-and-play? Do you think I could get away with fitting a secondhand unit or would it throw the electronics into turmoil without being coded? Mark Thompson

The system should default to auto mode when the ignition is turned on, with the settings remembered. My BMW literature does advise that the unit needs to be coded after replacing the control panel, so this would seem to be the case. If you were to have the unit repaired it should not need recoding.

BMW heater units normally give few problems. However, one component that does cause problems is the final stage unit (FSU) or final stage resister, often referred to as 'the hedgehog' due to its design. The fact that the blower will switch back on after being turned off is a classic symptom of FSU failure.