A/C Fan Blower Question?
Thread Starter
Instructor
Joined: Mar 2008
Posts: 221
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From: Farifax Station VA
A/C Fan Blower Question?
The A/C fan sounds strong and sounds like it is moving good air, but very little comes out of the vents. So a few months ago I had the dash out and all of the A/C ducting removed...I cleaned it all out, fixed a few vac lines and put everything back together. Still the fan doesn't move any air. Could there be a valve or something that is diverting the air outside the car? thanks
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
It's common for it to come out the heater vents at bottom instead- check that.
I wrote this up awhile back for that.
On at least later C3 the problem is that heater is the default position (no vac. or vac. leak) due to being designed in the north. Vent should be default. Very safe bet the problem is 1 OR 2:
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood alarm switch into wiper valley. Replacing most of engine side w/ hose will fix. OR
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease to fix.
3) If you have a heater, the small vac. tube to heater hose valve underhood probably also needs replacing. Block w/o heater.
PS The design problem comment is not intended to be offensive to any of our northern friends.
I wrote this up awhile back for that.
On at least later C3 the problem is that heater is the default position (no vac. or vac. leak) due to being designed in the north. Vent should be default. Very safe bet the problem is 1 OR 2:
1) The vac. line from engine is damaged from heat - a small plastic tube that goes in below the hood alarm switch into wiper valley. Replacing most of engine side w/ hose will fix. OR
2) The vac. switch itself is not switching due to vac. leak as the usually plastic rivet is not holding the 2 main switch parts together well. Besides replacing, it is also possible to tighten this &/or lube w/ a thin layer of white lithium grease to fix.
3) If you have a heater, the small vac. tube to heater hose valve underhood probably also needs replacing. Block w/o heater.
PS The design problem comment is not intended to be offensive to any of our northern friends.
Drifting
Joined: Jul 2008
Posts: 1,873
Likes: 27
From: Sonora CA
I had the exact same problem on my 73 SB with AC, Very little air out of any vent, at any setting.
I finally found out that there was more air being blown into the engine compartment than into the cabin. Too many leaks around the AC box on the firewall, especially the condensate drain on the bottom of the box. Now I get all kinds of air out of the vents.
Although I still haven't figured out why the highest speed doesn't work on the blower.
I finally found out that there was more air being blown into the engine compartment than into the cabin. Too many leaks around the AC box on the firewall, especially the condensate drain on the bottom of the box. Now I get all kinds of air out of the vents.
Although I still haven't figured out why the highest speed doesn't work on the blower.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Race Director
Joined: Apr 1999
Posts: 11,520
Likes: 13
From: CORVETTE 77 385 C.I. TEXAS
There is a dk. blue wire in the diagram that is the high blower relay trigger wire. (Mine is orange at the relay.) Note there is also another dk. blue wire shown.
W/ key on & blower on high check for power at the dk. blue wire at relay.
Yes, check fuse, relay & Gnd.
No, check switch & wiring.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
One of the first things I do only because its easy is to turn the switch to high and give the relay a little tap with a wrench. Seems like 50% of the time the blower comes on. You still need to replace the relay though.
