77 guys, environmental controls
Thread Starter
Racer
Joined: Feb 2008
Posts: 427
Likes: 32
From: North Alabama
St. Jude Donor '24-'26
77 guys, environmental controls
I think most 77 owners will agree that the environmental controls for this particular year stink. Specifically the selector switch. Its all vacuum actuated and just poorly conceived. So, has anyone come up with an alternate, custom or "trick" way to improve this functionality?
After an LS swap I decided on no A/C and just wanted to simplify the system to Heat only so I'd still have a defrost function. I purchased an A/C delete heater box from a forum member and I tested it before install. It worked fine, but even a new selector switch won't direct the air properly. I don't think its even activating the valve out under the hood to cut off the hot coolant supply to the core, because I'm getting way too much heat inside the cab. For these summer months I've got to find a way to improve this system.
Ideas?
After an LS swap I decided on no A/C and just wanted to simplify the system to Heat only so I'd still have a defrost function. I purchased an A/C delete heater box from a forum member and I tested it before install. It worked fine, but even a new selector switch won't direct the air properly. I don't think its even activating the valve out under the hood to cut off the hot coolant supply to the core, because I'm getting way too much heat inside the cab. For these summer months I've got to find a way to improve this system.
Ideas?
Last edited by MakoShark77; Jun 14, 2018 at 08:34 AM.
Racer
Joined: Jan 2017
Posts: 271
Likes: 120
From: Rock Hill South Carolina
I think most 77 owners will agree that the environmental controls for this particular year stink. Specifically the selector switch. Its all vacuum actuated and just poorly conceived. So, has anyone come up with an alternate, custom or "trick" way to improve this functionality?
After an LS swap I decided on no A/C and just wanted to simplify the system to Heat only so I'd still have a defrost function. I purchased an A/C delete heater box from a forum member and I tested it before install. It worked fine, but even a new selector switch won't direct the air properly. I don't think its even activating the valve out under the hood to cut off the hot coolant supply to the core, because I'm getting way too much heat inside the cab. For these summer months I've got to find a way to improve this system.
Ideas?
After an LS swap I decided on no A/C and just wanted to simplify the system to Heat only so I'd still have a defrost function. I purchased an A/C delete heater box from a forum member and I tested it before install. It worked fine, but even a new selector switch won't direct the air properly. I don't think its even activating the valve out under the hood to cut off the hot coolant supply to the core, because I'm getting way too much heat inside the cab. For these summer months I've got to find a way to improve this system.
Ideas?
My approach for now is to see if i can resolve the leaks by refurbishing the control switch. I'm polishing the mating surface that directs the vacuum so as to get a better seal. I initially bought a new switch, but that one leaked right out of the box too. All my hoses are good and the actuators do what they ought to when tested individually, so the problem has to be at the control end.
I'd also be interested in finding out if anyone else out there has a better way. The vacuum system sucks. Haha.
Safety Car
Joined: Oct 2007
Posts: 4,378
Likes: 1,740
From: Seattle Area Washington
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,595
Likes: 7,042
From: New Or-leens Loo-z-anna
Rookie suggestion about the "heat box" under the dash: Decide if you want vacuum or electric controls/install TWO new identical On-Off valves (both vacuum or both electric) in the firewall heater hoses--one in the supply & one in the return (it's a debatable whether the extra valve is needed, but I think it does a better job of keeping hot water out of the heater core).
As for the vacuum control switch, you probably know the smoothing process is called "lapping", which requires a piece of surface-ground marble about 6" x 6" or larger/apply lapping compound to the surface and move the control piece in a "figure 8" pattern until the surface has an even appearance/no low areas....then use a finer lapping compound. Once both control pieces are lapped smooth and wiped clean, apply a very thin coat of silicon grease and smooth it over the lapped surfaces (I do not know if there is a small spring or thin wavy washer that holds the two haves together but there should be in order to keep a constant seal between the lapped halves.)
I hoped that helped solve a couple problems
As for the vacuum control switch, you probably know the smoothing process is called "lapping", which requires a piece of surface-ground marble about 6" x 6" or larger/apply lapping compound to the surface and move the control piece in a "figure 8" pattern until the surface has an even appearance/no low areas....then use a finer lapping compound. Once both control pieces are lapped smooth and wiped clean, apply a very thin coat of silicon grease and smooth it over the lapped surfaces (I do not know if there is a small spring or thin wavy washer that holds the two haves together but there should be in order to keep a constant seal between the lapped halves.)
I hoped that helped solve a couple problems
Last edited by doorgunner; Jun 14, 2018 at 11:15 AM.
Thread Starter
Racer
Joined: Feb 2008
Posts: 427
Likes: 32
From: North Alabama
St. Jude Donor '24-'26
A good write up on the vacuum control switch.
https://www.corvetteforum.com/forums...on-switch.html
https://www.corvetteforum.com/forums...on-switch.html
Thread Starter
Racer
Joined: Feb 2008
Posts: 427
Likes: 32
From: North Alabama
St. Jude Donor '24-'26
Rookie suggestion about the "heat box" under the dash: Decide if you want vacuum or electric controls/install TWO new identical On-Off valves (both vacuum or both electric) in the firewall heater hoses--one in the supply & one in the return (it's a debatable whether the extra valve is needed, but I think it does a better job of keeping hot water out of the heater core).
As for the vacuum control switch, you probably know the smoothing process is called "lapping", which requires a piece of surface-ground marble about 6" x 6" or larger/apply lapping compound to the surface and move the control piece in a "figure 8" pattern until the surface has an even appearance/no low areas....then use a finer lapping compound. Once both control pieces are lapped smooth and wiped clean, apply a very thin coat of silicon grease and smooth it over the lapped surfaces (I do not know if there is a small spring or thin wavy washer that holds the two haves together but there should be in order to keep a constant seal between the lapped halves.)
I hoped that helped solve a couple problems
As for the vacuum control switch, you probably know the smoothing process is called "lapping", which requires a piece of surface-ground marble about 6" x 6" or larger/apply lapping compound to the surface and move the control piece in a "figure 8" pattern until the surface has an even appearance/no low areas....then use a finer lapping compound. Once both control pieces are lapped smooth and wiped clean, apply a very thin coat of silicon grease and smooth it over the lapped surfaces (I do not know if there is a small spring or thin wavy washer that holds the two haves together but there should be in order to keep a constant seal between the lapped halves.)
I hoped that helped solve a couple problems
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,595
Likes: 7,042
From: New Or-leens Loo-z-anna
I thought it wouldn't be a hassle, but it got old fast
