on my 72 riviera the blower motor spins up when i put the key in accessory but no air comes out of the vents. I would say there is a good chance the heater / fan controls are toast because they move really had but the fan seems to spin fine and has 12 volts so i assume it's stuck on high. The vents have not worked since i bought the car.
Generally the top fan speed uses the high speed fan relay circuit while the lower speeds have their own circuit. A problem I have seen is overheating of the wiring and burned wiring at the high speed relay generally mounted on the firewall. Both circuits use this relay to feed the fan. It could also be the resistor array in the air box under the hood or the switch on the dash. The other issue of no air in the cabin is likely a cable or pneumatic issue with the controls to the air box diverter doors. But first check under your dash to make sure your duct work is in place.
@flynbuick thank you if its getting 12 volts at the fan its on high speed correct? if it was on the low speed circuit it would be getting less voltage? My main initial concern is just getting air to come out into the cabin and will work on being able to control that air after
Your issue with a lack of low speed fan is upstream from the blower motor. Look at the high speed fan relay. If the wires at the terminals do not look fried pull and examine the resistor array located the AC box under the hood.
@flynbuick sorry if i'm being dense here with what your trying to tell me. I really appreciate your help. I'm not wiring expert at all, but i'm not at all concerned with lack of speeds just the fact that no air comes out of any of the vents in the car, I would for the moment be perfectly fine with it being stuck on high so long as air came out of the vents, so i'm trying to eliminate the fan not spinning fast enough as a cause for that. The fan is getting 12 volts that means it's on high correct? if it was on low it would get less than 12 volts? Also there is no A/C in this car one of only 300 made without it.
Check to make sure all the air is not coming out the floor/ heater. If no air at all is coming out, start checking for blockages (mouse houses). Fan squirrel cage just spinning on the fan motor shaft?
@ap1672 thank you. I checked all the vents including floor can't feel anything except maybe a small trickle. Iv completely removed the fan and motor and everything is fine there it seems. As far as i can reach from there i find no blockages of any kind have not gone so far as to tear the whole dash apart to check in there yet though so i can't completely rule out mouse related blockages, but i have seen no evidence of mice in the car anywhere. Thats why i was trying to rule out the fan not blowing enough air first, it is looking like though that a blockage is becoming more likely.
