Need diagnosis help with the AC vent control, AC only works on norm setting
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,377
Likes: 384
From: Leland , North Carolina
Need diagnosis help with the AC vent control, AC only works on norm setting
On my 1980 AC /heat works great on all settings except AC MAX setting. Blows fine on the NORM setting but quits as soon as i slide it to MAX AC .
The slider vacuum switch is brand new. Any ideas what or where it's failing. ?
The slider vacuum switch is brand new. Any ideas what or where it's failing. ?
Burning Brakes
Joined: Sep 2020
Posts: 796
Likes: 794
From: Chapin SC 29036
I am not sure about the later years, but early C3's run an Orange wire with a 30-amp inline fuse to a relay mounted on the side of the A/C box so that the necessary current to operate the fan and the AC compressor don't damage the switch. It might be as simple as that.
Thread Starter
Melting Slicks
Joined: Jun 2011
Posts: 2,377
Likes: 384
From: Leland , North Carolina
My AC blows fine on NORM setting. Ac compressor is on with the MAX and NORM settings ..When I slide it to the MAX setting the air stops blowing out of the vents. Not sure if there is some vacuum flapper stuck somewhere. It's got to be something simple, I'm just not sure where to look...
Safety Car
Joined: Oct 2007
Posts: 4,360
Likes: 1,724
From: Seattle Area Washington
My AC blows fine on NORM setting. Ac compressor is on with the MAX and NORM settings ..When I slide it to the MAX setting the air stops blowing out of the vents. Not sure if there is some vacuum flapper stuck somewhere. It's got to be something simple, I'm just not sure where to look...
Burning Brakes
Joined: Sep 2020
Posts: 796
Likes: 794
From: Chapin SC 29036
Are you talking about the Fan speed switch or the Rotary Wheel that changes from AC to Vent to Heat? The Fan Speed switch is an electrical device and the Rotary Wheel is mostly Vacuum control. In the AC mode it does turn a switch on to turn on the compressor. The Vacuum controls the flaps that control where the air is being routed to. I am including a diagram for the AC wiring and vacuum. It was made for my 69, but as far as I know there were almost no changes in the function.
Do you have a wiring diagram for your 80? I have a B/W diagram that looks pretty good. On the older years I have redrawn many of the B/W diagrams to color and fixed a few of GM's mistakes, but I haven't done any after 1969. If you would like a copy, let me know and I will add it here.
Do you have a wiring diagram for your 80? I have a B/W diagram that looks pretty good. On the older years I have redrawn many of the B/W diagrams to color and fixed a few of GM's mistakes, but I haven't done any after 1969. If you would like a copy, let me know and I will add it here.
