Outstanding! Thanks Scot.

No kidding? I don't get heat until the emgine (sic) warms up? Weird. Volvo thinks that the ACC does monitor coolant temp, I think I'll go with them on that one. I know where the gauge and ECU sensors are, the gauge sender is not used by the ACC if the ACC uses the ECU sensor, it would have to be through the ECU, I do not believe that is the case. Seems to me I would have drivability issues if the ECU never saw the engine temperature. Someone correct me if I am wrong.

For anyone else that has useful input, I found on further reading that the fan runs in automatic if either the coolant temp is above 95*F or the cabin temp is above 64*F. It would appear that the reason my fan eventually runs in auto is because the cabin temp gets above 64* from my putting the heat control on defrost (runs the fan on high no matter the coolant temp). So this further reinforces the idea that the coolant temp sensor is bad. I suppose it could be the ACC module. Am I the only one to ever have this problem?

My 1984 764 had three temp sensors r/t the ACC. One for the outside temp is mounted in the intake plenum above the fan. You can get to it by removing the cowl cover...that covers the wiper motor- most likely not you problem. Then there is the one mounted in the dash behind the mini grill above the glove compartment that has a tube venturi that draws air into it and measures the inside temp. The one you are looking for is actually a temputure switch that is mounted in the heater hose and allows the system to start in auto mode after it reaches a certain temp.- this is near the coolant flow valve behind the engine near the firewall. If you hit the defroster that overrides this sensor. However in auto this sensor or switch needs to reach a certain temp for the system to start in AUTO. Mine was a V6 car but I have looked at several of these over the years and this is what I remember. One guy I knew had a problem with the "programmer" which is nothing more than a motorized vacuum control mounted behind the glovebox. He said he was able to take it apart and lube the motor and valves to fix his problem. In 1988 they came out with the ECC which was a totally different system. However it also had a delay that would wait until a certain temp was reached before the fan would come on and slowly sped up as the temp increased. This is also how your owners manual will explain the AUTO mode. I would think you could "bypass" that sensor and trick the system into thinking there is warm water...Good Luck Scot