Car Climate Control Issue

I have a 1996 Mazda Millenia that developed a sudden climate control issue. This vehicle has the setup where I select the desired inside temp and the system selects cool or heat and the fan speed. Suddenly, when I push the “on” button, it acts like the system is working, but does not change teh air temp coming out of the vents. For instance, if I turn the system on and set the temp at 65 F, the fans kick on high. As it rotate the selector knob to increase the desired temp, the fan slows until I exceed teh inside temp. At that point the system switches to heat but no change in air temp. It thinks it’s working, but it’s not.

Since it affects both A/C and heat, I don’t think it is an issue with either. I suspect a bad relay or switch somewhere. Has anyone experienced this issue and have a good idea where to start? I hate chasing down electrical issues…

Good chance the air mix door (temperature blend door) in the ductwork is not moving. If so, most likely a faulty air mix actuator.

Thanks, Gary, that sounds like a good place to start. I’ll peruse the service manual and map out a plan.