Electrical problem
1999 Dodge Truck V8 Four Wheel Drive Automatic 315000 miles

i recently got this ram 1500 and the air vents don't work it only blows air trhu the defrosting vent(top).i wonder what is wrong my ac doesnt turn on either.it is like the top nob doestn do anything(there are 3 nobs top is for off-max ac-top ac vent-mix vents top n floor-floor-floor vent defrost n defrost middle is for fan speed n button for cold/heat n the mirror defroster button)well it doesnt matter in which setting i turn the nob because it only blows air trhu the defrosting vents. please give me an idea of what the problem might be thank you.