Hi all, been digging around the forums but haven't found an answer yet so I thought I'd post. I have an '81 with A/C and have the interior out as well as the heater core. Getting ready to put it all back together but wanted to make sure my heater and air selector switch is working properly. I have my hand held vacuum pumper and was going to hook it u to the main black vacuum line coming into the #1 port on the control mechanism to check that all the doors and such are working when going through the selections. Anyway, when I hook into the black line and pump the vac, I cannot get any vacuum. The switch is letting air in? How do you test the switch with a manual pump? I'm looking at the diagram but not sure I'm reading it correctly. With the selector off, what does Port 1 = Seal mean? Does Vent mean that there is no vacuum but that port is open? VAC I'm assuming means there should be vacuum on the port. I've already tested all the valves individually and they all work.. Now I just want to apply vacuum through the black line then run the selector thru it's paces and see if the doors and water cutoff valve is working properly. Seemed easy enough in my head but it's not working as I thought it should. Thanks for the help.

 

I can't answer the question about the right way to test for proper functioning, BUT what I do know is that it's quite common for these to not hold a vacuum after the grease inside dries up over the years.

New HVAC selector switches are usually sold WITH any of the "high vacuum grease" that you need to add before installation. (I have brand new one and a small pot of the high vacuum grease sitting here and it's on my todo list, but WAAAY down the list...) Willcox Corvette sells them pre-greased for a decent markup if you can't be bothered.

If you can't find anyone else who knows how to troubleshoot them, I'd give Willcox a call; they're really good at troubleshooting procedures. They MIGHT even have a YouTube video on this, but I didn't find it in a very brief search.


Adam

 

I understand that Willcox is gone out of business!

 

Yes it appears Wilcox is down and out unfortunately. I'm assuming seal means that port is blocked. VAC obviously means vacuum present and I'm going to assume VENT means the port is open but no vacuum. I'll fool around with it some more and see if it works like I think it should. I have some silicon grease I can try if it doesn't appear to be working.

 

Here is the post where a Forum Member repaired his vacuum switch, unfortunately I am not tech savvy, and know how to copy/paste from my saved emails.


There is also a photo of the special grease he used.

 

https://www.corvetteforum.com/forums...-switch-2.html
i just used

 

I think I have figured out how to test his in case someone else is looking. My whole goal was to test all the circuits without having to run the engine and using my hand held vacuum pump. So from the diagram I posted, with all the switches in the Off position, port 1 should be sealed and hold vacuum while all the other ports are open, no vacuum. This means all the diaphragms are in the normal non-vacuum positions. So if I put the vacuum pump on the black line coming into Port 1 and the sliders in the off positions, I should be able to get and hold vacuum. At this time, that's not happening so I'm assuming the switch is leaking.

@interpon I saw your thread. I don't recall seeing what size screw and what size drill bit you used. Do you recall?

 

Good luck trying to use a hand vacuum pump...
These vacuum switches are designed to vent (exhaust) out the two halves as shown above in the repair tip post ...
Look at the vacuum manifold hose connector.
#2 needs to be capped and sealed off completely.
A/C cars are ported differently from Non A/C cars but same vacuum switch.
If you put the function slider where the vacuum switch is in my photo below you should also be able to pull and hold a vacuum.
Also in the OFF position should hold a vacuum...
Notice Port #2 is capped...