I have a 99 S80 which gives me a warning light show (ABS, STC, transmission service, emmission service, powersteering, etc) once the outside air temperture starts getting hot (no problem during the winter months). OBDII codes 1550, 1618 and 722 are usually set, leading me to believe that the ABS control module is loosing it's speed output signal when it gets hot. I know that the ABS module is a problem child, but I've also noticed that my electric cooling fan only runs when the air conditioner is on. It used to run for a little while after the car was turned off -- it does not appear to do that now, and does not appear to run when the air conditioner is not on. The engine temperture gage always shows a normal temperture, but the underhood temp does seem to be very hot compared to other cars I own.

Is it possible that the fan is not working right and causing the ABS control module to get overheated and malfunction? How can you check that the fan is working correctly? Thanks in advance for any help you can give me.