drwet

Turned on the air conditioning for the first time this year the other day. Blower motor doesn't work with the air conditioning on. Only have the (always on) low speed. The blower motor works fine on all speeds when I select heat or vent, but not on the A/C setting. I pulled out the wiring diagram and it looks like there is no possible cause for this except the control itself. Can anyone think of any possible reason for this other than a problem with the heater/air conditioning control assembly?

mikem350

Looks like the control itself

0Willcox Corvette

Check the high blower relay... Check the wire for corrosion inside the connector too... It's a common problem.

drwet

[QUOTE=Willcox Corvette;1592333570]Check the high blower relay... Check the wire for corrosion inside the connector too... It's a common problem.
QUOTE]

How does that explain the fact that it works perfectly on vent and heat, but not on A/C? Isn't it the same blower relay in both positions?

0Willcox Corvette

Does it actually blow on high speed in Vent and heat? If so then the issue is somewhere else, I guess I missed that in your original post.. But.........

That makes no sense either... because the blower fan speed is controlled by the blower switch. Go to the 52 circuit with the car in high blow on AC... see if you have power... If you do then again.. look at the relay, it's a simple circuit that can be deceiving. See, the 52 wire can only receive power from the yellow 51 circuit wire at the control switch... But for it to only do this when not on AC is going to require you to dig a bit deeper. That would be where I'd start and then work my way backwards.

-Willcox

Blue79

Where is the hi blower relay located on a 79?

0Willcox Corvette

Engine compartment mounted above the AC box on the firewall.

BB 73

drwet, did you get to the bottom of your problem? I'm experiencing the same thing on my 73?? It makes no sense I have high blower function on everything but Max AC?? Thanks in advance.

newbie2vette

Had the same problem with the 79 I restored last year and the same with a friends 79. It is the wires or connectors under the top switch. The switch to select AC or not. gain access to that and clean the connectors or pinch them a little so they are tight.

drwet

No I did not solve the problem exactly. It went away on its own and has not yet recurred. I fully expect it will. My suspicion is it is within the HVAC selector switch. Some problem with it not making proper contact, but until it happens again, it kind of hard to track down.

drwet

That makes sense to me, I suspected the problem was in there somewhere.

BB 73

Thanks, I will rip that apart tonight. I was pulling my hair out cuz it does not make sense I hope that's the case :-)

BB 73

I found a floating hot ground wire, fixed that and now the ac works in all settings including high but now my heater/fan doesnt work on any setting. Chasing all my wires at this point. Not sure what past owner/40 years did to my wiring.