1980 Defroster delima
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
1980 Defroster delima
Hopefully somebody has seen this before. The Heat/AC control unit will not change the fans air direction from from the bottom vent to the defroster or the upper vents. I took the plug off the back of the switch and applying vacuum to the three vent hoses, I can get the air to divert. The defroster and vent will work. If I take a hose from the source vacuum on the plug and connect it to each of the three hoses (with the engine running) the engine vacuum will work the other vents. Hook the switch back up and nothing, It's a new switch, is this just another Chinese made part?
Melting Slicks
Joined: Jun 2014
Posts: 2,236
Likes: 498
From: NJ
Did you check the vacuum reservoir? It could be cracked. Some are metal cans and some are black plastic. Also do you have vacuum at the control head? I believe there is a Vac Sw. on the fan speed selector which directs vac. to the mode selector (heat, vent. defrost,etc) once a fan speed is selected. Also, there may be a heater valve for the heat core which shuts off coolant flow to the core when the temperature lever is at cool (far left position). Any one of these lines has a leak it will bleed off vacuum from the system. Start at the intake manifold Vac. fitting and follow the vacuum lines.
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
If you can get the defrost to work with your vacuum pump then I'd take a good look at that switch.
Its common for the vacuum select switches to fail even when new and even when GM made them. They are just two plastic halves held together with a plastic rivet and a tension spring. First I would try a small drop of oil in one of the tubes and work it around to see if it will seal it up. If it doesn't then I'd return the switch for a replacement.
Willcox
Its common for the vacuum select switches to fail even when new and even when GM made them. They are just two plastic halves held together with a plastic rivet and a tension spring. First I would try a small drop of oil in one of the tubes and work it around to see if it will seal it up. If it doesn't then I'd return the switch for a replacement.
Willcox
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Hopefully somebody has seen this before. The Heat/AC control unit will not change the fans air direction from from the bottom vent to the defroster or the upper vents. I took the plug off the back of the switch and applying vacuum to the three vent hoses, I can get the air to divert. The defroster and vent will work. If I take a hose from the source vacuum on the plug and connect it to each of the three hoses (with the engine running) the engine vacuum will work the other vents. Hook the switch back up and nothing, It's a new switch, is this just another Chinese made part?
Over time the 7-terminal rubber plugin gets stretched and will no longer seal vacuum to the zinc switch. I cut the hoses off my plugin one-by-one and plugged them directly onto the switch and that did the trick. To make sure I never crossed the hoses I labeled each one with masking tape and a Sharpie felt pen and also drew a diagram showing where each hose plugged onto the switch and kept the diagram under the console for future reference.
Thread Starter
Burning Brakes
Joined: Jan 2012
Posts: 943
Likes: 73
If you can get the defrost to work with your vacuum pump then I'd take a good look at that switch.
Its common for the vacuum select switches to fail even when new and even when GM made them. They are just two plastic halves held together with a plastic rivet and a tension spring. First I would try a small drop of oil in one of the tubes and work it around to see if it will seal it up. If it doesn't then I'd return the switch for a replacement.
Willcox
Its common for the vacuum select switches to fail even when new and even when GM made them. They are just two plastic halves held together with a plastic rivet and a tension spring. First I would try a small drop of oil in one of the tubes and work it around to see if it will seal it up. If it doesn't then I'd return the switch for a replacement.
Willcox
Thank you for being a company that cares!
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
It' a new switch that I purchased from you folks. I tried another new switch from a local corvette guy with the same results. So, I gave your info number a call. I apologize for not remembering who I spoke to, but he was very patient. I know that Willcox is not just a supplier but also has an active shop. You guys don't make these parts but you have to work with the same quality. The gentleman I spoke to actually walked out into the shop area and came back with an answer. The answer actually worked!
Thank you for being a company that cares!
Thank you for being a company that cares!
glad you got it fixed. Willcox
