The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - How do I tell if this is good and working?

Murphy IRE · 05-03-2010, 10:55 PM

After a lot of research. GM has had problems with this design, but it was great for sales; because everyone replaced all the other valves before finding the real problem! There is a cheap diaphram gasket on the inside. It holds vacuum and allows the vacuum to directed from one system to the other. Apparently, in 1992 on the inline 4cl Chevy Cavalier they were still using this part. Same on 84 Olds. I'm sure they aren't an exact fit. I found a sight in CA that specializes in corvette parts and the top half, it appears to be identical; but the bottom linkage is different (A possibility for a mix and match}. I will try the dealer on the Olds and Cavalier info in the morning. The name was changed to "Rotary Switch" for the vacuum control valve on the heater switch. If they don't work. The Germans on 64-72 Benz's have an electronic assited vacuum valve. Turn it off or on to direct the vacuum. You can buy new from a place in AZ or go to the local Benz JY and pull for a lot less. Apparently they have a longer life. I'll update with the final solution.

05-03-2010, 10:55 PM	#7
Murphy IRE Registered User Join Date: Oct 2009 Location: South Denver Metro, CO Posts: 385	Re: How do I tell if this is good and working? After a lot of research. GM has had problems with this design, but it was great for sales; because everyone replaced all the other valves before finding the real problem! There is a cheap diaphram gasket on the inside. It holds vacuum and allows the vacuum to directed from one system to the other. Apparently, in 1992 on the inline 4cl Chevy Cavalier they were still using this part. Same on 84 Olds. I'm sure they aren't an exact fit. I found a sight in CA that specializes in corvette parts and the top half, it appears to be identical; but the bottom linkage is different (A possibility for a mix and match}. I will try the dealer on the Olds and Cavalier info in the morning. The name was changed to "Rotary Switch" for the vacuum control valve on the heater switch. If they don't work. The Germans on 64-72 Benz's have an electronic assited vacuum valve. Turn it off or on to direct the vacuum. You can buy new from a place in AZ or go to the local Benz JY and pull for a lot less. Apparently they have a longer life. I'll update with the final solution.