My HVAC is dead in the water I am think it is electrical. I have tried 2 HVAC panels and get nothing out of both. There is a yellow wire that runs into the fan speed selector and it does have 12 volts. I also have 12 volts at the red wire on the relay. I do not have any power anywhere else. I am not sure how the circuit is set up for the HVAC controls so if anyone has any experience with it then please offer up some suggestions. Also, if you have a wiring diagram then please post it. I have 91 model year Z28.