After reading through this thread:

http://www.brickboard.com/AWD/volvo/1364544/850/blower_motor.html

I'm starting to feel a little concerned about the state of the components in my own car. As I have posted here: http://www.brickboard.com/AWD/volvo/1359088/850/compressor_wont_start_evaporator_replacement_ac_compresssor_clutch.html
I had some faults in the AC system (faulty AC relay and AC control unit). What isn't mentioned there is that I had to replace the blower fan power stage about a month or two before the evaporator replacement, because of the exact same symptom RTBimmer describes - the fan kept running with ignition off. At the same time the engine temperature sensor failed and apparently the engine ECU also had a failure, because after replacing the temp sensor and power stage I still got a an error code (can't remember which one) and the Lambda light came back after each reset until I exchanged one of the engine ECU's for a used replacement.

It could be, that all this components failed at once. I know for sure that the engine temp sensor and blower fan power stage did fail at the same time, because the lambda light went on suddenly while driving and the fan started blowing, although it was previously off. It might be that the other components (AC relay, AC control unit and as I later discowered also the engine cooling fan relay) all failed at this same time, I just hadn't noticed until I tried to use the AC.

Now to my concern. Is it possible that a short caused this failures? If so, is it possible that even though I replaced the components I haven't found the source of the short and the potential for the same short is still out there somwhere? Should I chechk this somehow, and where should I look? The car runs excelent now, everything works and no codes show, but what if it's just a disaster waiting to happen (again)?