Does your car have a (ATC) Automatic Temp Controller? Has the digital read out of what you have it set on? If so Turn temp until it displays 75 degress then hold in just the upper row of buttons except the A/C button all at the same time it will began to flash and test the system and show you the codes at the end of the test if there is any. I got a new ATC from a giy that rebuilds them off of EBAY. Only like 41.00 and warrranty for a year you just send him your old one like a core exchange. Watch who you buy from! Don't buy the same problem you already have.