My '89 5.0 VIN 'E' TBI 5-speed runs hot. I have tried EVERYTHING I know, and nothing seems to work. My scan tool tells me that when I turn the AC on, that request is not received by the computer. I don't know if this is contributing to my overheating problem, but until I resolve it I won't know for sure. How do I troubleshoot this 'AC not requested' signal?

 

The electric cooling fan should operate with the A/C on. If not, there is a problem. I believe with your setup, the fan is controlled by the A/C switch and the thermal switch in the head - not the computer.

Tim