I have a 79 Corvette that the fan speed stays on low just like when key is switched on ..even when in max ac and norm ac ..only time it will speed up is when I go to vent mode or floor mode or defrost ..I have tried fan switch , resistor and blower relay ...also car has just had a NEW heater / ac control panel installed not sure if fan worked before this its a customers car ,, Notice they do offer control panel just for 79 and then for 78 and back any ideals or thoughts

 

Welcome to the forum.
So you are saying that the blower speed stays on low no matter what position the blower speed switch is in, correct? If that is the case, you need to get a voltmeter and start tracing down voltages.

 

yes correct .. I think the problem is ac control panel they sent me wrong year they are difference between 76-78 and the 79 way the terminals are on the selector switch I have correct one on way I needed 79 they had asked build date but sent one for 78 back ..I will let you know thanks