I had intermittent coolant heating problems. replaced thermostat and fan clutch on radiator fan, still had problem. Read posts and archives on temp compensating board, but doubt it is source of problem because as soon as I turn the heat on full blast, the needle immediately returns to the 9 o'clock position..tells me the guage is working and responding properly.

Yesterday discovered AC condensor cooling fan not working. Connected 12 volts directly to fan, fan turns strong. Found AC fan relay (under coil on driver side fenderwall) and tested it. Applied 12 volts directly to coil, the coil closed the contacts to send power to the fan. Problem is, with the car running and the AC on, the relay does not close. According to my wiring diagram, the other side of the coil is grounded by a temperature switch.

Can anyone tell me where this temperature switch is located on a 91 240? I disconnected the thermal switch on the dryer/receiver and when I reconnected it, the only thing it did was energize the AC compressor clutch.

thanks for any help or advice.