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Hello everyone, after deciding to tackle the heater box and blower motor I ran into some problems. I can't seem to find 3 parts that I would like to replace while I have the heater box out. The first one is this vacuum type switch ontop of the box; not sure what the real name is and my phone is not letting me post pictures but it has 3 vacuum ports (two are being used but the third has no vacuum line?)
The second one is the A/C diverter valve actuator. It operates somewhat ok on the finger over the port test but it only opens the blend door about 25% of the way; I've found one on the internet with a GM part number but no current ones in production it seems. (PN# 1996595)
Last but not least, the heater core blend door; the rubber has rotted away there is quite a big gap in between the door and the heater box.
I believe it to be crucial for me to replace these parts as they are quite old and seem to be failing or not operating correctly, would anybody have any ideas of where I can get these parts?
Before spending the resources looking for and purchasing a new switch you should first test, and if needed clean and re-lubricate with the correct Vacuum Grease your current Vacuum Switch.
On the Vacuum switch you will have 3 ports, from left to right lets name them port 1 - 2 & 3.
Port 1 is the vacuum port going to the Hot Water Shutoff valve on the 5/8" heater hose in the engine compartment.
Post 2 is the Main Vacuum feed to the Vacuum Switch.
Port 3 is unused and serves as the exhaust port,
Using a vacuum cap, cap off Port 1
Using a hand vacuum pump attach that to Port 2.
A couple pumps of the vacuum pump should pull a vacuum, now does the switch hold a vacuum?
If the switch holds a vacuum the switch is good...
Press the little spring loaded button at the end of the switch and the vacuum will exhaust through Port 3.
This is hot the Hot Water Shutoff valve opens and closes in the 5/8" hose in the engine compartment.
If not follow the steps below...
These switches can most times be saved by a good cleaning and re-lubricated using the correct vacuum grease.
To open and clean the switch push down the little plastic stop of the valve plunger (RED ARROW)...
Pull the plunger out of switch housing...
Caution: there is a spring inside so don't loose that.
Carefully clean the rubber pad and spool and re-grease, reinstall spool into switch housing.
You can get a 1/2oz.of the correct vacuum grease at amazon that will last you for a very long time LINK:
Very interesting I did not expect these to be saved so easily, thank you very much for explaining this process and including pictures Joe; I will try it in the next few days when I have some spare time again. Also on an unrelated note; I did manage to find and purchase a remanufactured ECM for this vehicle just to try it out, but it came without a prom and chip. Do they sell newer proms and chips or would I have to hunt down some used ones to throw into the ECM?
1981 Corvette A/C Parts
