I have an 88 with a new heater core and a/c compressor. The a/c randomly stopped working the other day along with the heater. When you turn on the a/c it makes the pressure building noise and the rpms go up like any a/c but it doesn't blow any air at all, neither does the heat. I checked the fuses and other then that I'm really not sure what to check. Any advice would help a lot thank you

 

Check your blower motor - it'll be in the HVAC compartment with the heater core and condenser coil. Disconnect it, take a digital multimeter to it, test it for resistance. If it shows none, it's toast. Alternatively, you could hook a fused power source to it (for lack of a DMM) and see if it comes on. If not, it's toast.