1979 Resto-Mod HVAC Gremlins
Thread Starter
Instructor
Joined: Feb 2011
Posts: 161
Likes: 1
From: Edison NJ
1979 Resto-Mod HVAC Gremlins
First, thanks again to all who responded to my last post about the hazard/brake light electrical problem.
My wife and I are "resto-modding" a '79. We love the car and re-did the entire old dirty, cracked interior (from oyster to black). While it was apart we changed the heater core, hoses, etc. When we first got the car, none of the heater controls worked, so we changed the heater control box, underhood relay, and resistor. Now even with the heater in "off" the blower motor runs steady on low with the ignition on. The blower motor does run at all speeds as normal, but it will not shut off completely. I guess the only other thing it could be is the blower motor itself? Any ideas?
I tested the two vacuum door actuators under the dash and they were fine. I did not replece that valve above the heater core box with the three vacuum connections though. The cable-driven temperature control works fine, but the the HVAC will not switch ducting (i.e. from vents, to floor, to defrost). I am a bit confused with the system. It appears that it is actuated with vacuum. Is there a diagram or go-by somewhere for troubleshooting? Should I replace that vacuum valve and all the vacuum lines?
Also, anyone have the Patriot shorty/block-hugger headers? Any bad feedback on these? TIA
My wife and I are "resto-modding" a '79. We love the car and re-did the entire old dirty, cracked interior (from oyster to black). While it was apart we changed the heater core, hoses, etc. When we first got the car, none of the heater controls worked, so we changed the heater control box, underhood relay, and resistor. Now even with the heater in "off" the blower motor runs steady on low with the ignition on. The blower motor does run at all speeds as normal, but it will not shut off completely. I guess the only other thing it could be is the blower motor itself? Any ideas?
I tested the two vacuum door actuators under the dash and they were fine. I did not replece that valve above the heater core box with the three vacuum connections though. The cable-driven temperature control works fine, but the the HVAC will not switch ducting (i.e. from vents, to floor, to defrost). I am a bit confused with the system. It appears that it is actuated with vacuum. Is there a diagram or go-by somewhere for troubleshooting? Should I replace that vacuum valve and all the vacuum lines?
Also, anyone have the Patriot shorty/block-hugger headers? Any bad feedback on these? TIA
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
The blower motor is supposed to run all the time. I cannot say for sure without a drawing in front of me why, but the later C3 models run all the time.
Melting Slicks
Joined: Oct 2005
Posts: 2,056
Likes: 8
From: Redruth Cornwall
As Eddie has said, the blower will run constantly on low, its supposed to.
As for the Hvac controls, Willcox has this which will help.
http://willcoxcorvette.com/instructi...82_secured.pdf
and also,
Not sure about the headers.
As for the Hvac controls, Willcox has this which will help.
http://willcoxcorvette.com/instructi...82_secured.pdf
and also,
Not sure about the headers.
Last edited by jotto; May 5, 2011 at 05:35 PM.
Melting Slicks
Joined: Aug 2010
Posts: 2,487
Likes: 10
From: Palm Beach Florida
St. Jude Donor '12
They run to keep the exhaust gases out of the car. To keep it a positive air flow in the cabin. Otherwise you may exp. some of the fumes from the engine bay entering the cabin.
Racer
Joined: Dec 2009
Posts: 380
Likes: 0
From: Glendale AZ
The system is actuated by vacuum.
Here is a diagram thanks to Willcox Corvette, a sponsoring vendor. http://willcoxcorvette.com/instructi...82_secured.pdf
You're probably going to have to take the dash off to figure this one out. Go ahead and order the vaccum line kit because they are almost certainly shot. You may also need the vaccum switch for the AC control, but it's cheap so have no fear.
What you need to do is take the dash off and remove the front set of AC Ducts. This will expose the door (looks like cardboard or fiberboard) that switches from defrost/floor to vents.
The actuator that controls that door is on the back side of that box.
That's the one that needs to be working for different vent selections to work.
When you apply vaccum, you should see the door open.
Here is a diagram thanks to Willcox Corvette, a sponsoring vendor. http://willcoxcorvette.com/instructi...82_secured.pdf
You're probably going to have to take the dash off to figure this one out. Go ahead and order the vaccum line kit because they are almost certainly shot. You may also need the vaccum switch for the AC control, but it's cheap so have no fear.
What you need to do is take the dash off and remove the front set of AC Ducts. This will expose the door (looks like cardboard or fiberboard) that switches from defrost/floor to vents.
The actuator that controls that door is on the back side of that box.
That's the one that needs to be working for different vent selections to work.
When you apply vaccum, you should see the door open.
Thread Starter
Instructor
Joined: Feb 2011
Posts: 161
Likes: 1
From: Edison NJ
Thanks for all the assistance. This forum is great!
I just ordered a vacuum line kit and the vacuum control valve. I never would have guessed about the blower motor staying running on low. I spent a good two hours trying to troubleshoot all the wiring and connections for the heater!
I just ordered a vacuum line kit and the vacuum control valve. I never would have guessed about the blower motor staying running on low. I spent a good two hours trying to troubleshoot all the wiring and connections for the heater!
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Thanks for all the assistance. This forum is great!
I just ordered a vacuum line kit and the vacuum control valve. I never would have guessed about the blower motor staying running on low. I spent a good two hours trying to troubleshoot all the wiring and connections for the heater!
I just ordered a vacuum line kit and the vacuum control valve. I never would have guessed about the blower motor staying running on low. I spent a good two hours trying to troubleshoot all the wiring and connections for the heater!
Willcox
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Thread Starter
Instructor
Joined: Feb 2011
Posts: 161
Likes: 1
From: Edison NJ
Thanks again. I actually just ordered from you guys. Do you sell power window switches that don't die within a month?
