90 CHEVY SILVERADO 1500 4X4 TRUCK With DIGITAL CLIMATE CONTROL TEMP HEATER & A/C. Truck produces heat, but heater blower fan only blows air once in a while, blower level (high, med, low) doesn't make a difference, either it clicks on and works fine or it doesn't blow at all. I think the blend door doesn't work real well either because it will let cool air blow in depending on if I put the setting on defrost/upper vent, or put it down on the floor vent? Heat does come in from the engine which does make it tolerable, but with out fan blowing it in it isn't to good.