correct heater valve
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Registered User
Joined: Sep 2006
Posts: 147
From: Utah
I just pulled the one off the parts car that is a 72 cutlass, don't know if its correct because its open until I put vacuum to it then it closes and I thought i saw on here somewhere that its supposed to be normally closed until you put vacuum to it then it opens?
Old School Olds
Joined: Nov 2008
Posts: 9,266
From: Marble Falls TX
Old(s) Fart
Joined: Mar 2007
Posts: 50,698
From: Northern VA
That is a later normally open valve, so it's been replaced.
Registered User
Joined: Feb 2013
Posts: 15,360
From: Phoenix, AZ
Below is from an old post about this topic.
https://classicoldsmobile.com/forums...-valve-120656/
More information in this thread about the difference in vacuum and heater valve operation (normally open vs normally closed) for the A bodies. Note that this information is different than what Joe pointed out in the CSM, which claims the change was made in 1973 but actual measurements show it was made in 1971, which coincides with the changes in water pump nipple sizes and the heater valve thread size.
https://classicoldsmobile.com/forums...estion-108677/
1970 Supreme operation:
1971 Supreme operation:
https://classicoldsmobile.com/forums...-valve-120656/
I have the same valve on the shelf for my car.
It is stamped with:
TYPE H25
RANCO
COLO, USA
The backside has an ink label:
H25-124
The valve is normally open and takes vacuum to close.
Just today I was working on the car, changing the heater core and I'll install the new heater valve tomorrow. I connected a vacuum gauge to the heater valve vacuum hose on my car and it has no vacuum with the temp slider on WARM and vacuum with the temp slider on COOL, so this valve matches my car's vacuum operation.
I recommend you check the vacuum operation on your '72 to ensure it matches your heater valve as my '71 operates opposite of what the factory manual describes per Joe's posts.
It is stamped with:
TYPE H25
RANCO
COLO, USA
The backside has an ink label:
H25-124
The valve is normally open and takes vacuum to close.
Just today I was working on the car, changing the heater core and I'll install the new heater valve tomorrow. I connected a vacuum gauge to the heater valve vacuum hose on my car and it has no vacuum with the temp slider on WARM and vacuum with the temp slider on COOL, so this valve matches my car's vacuum operation.
I recommend you check the vacuum operation on your '72 to ensure it matches your heater valve as my '71 operates opposite of what the factory manual describes per Joe's posts.
More information in this thread about the difference in vacuum and heater valve operation (normally open vs normally closed) for the A bodies. Note that this information is different than what Joe pointed out in the CSM, which claims the change was made in 1973 but actual measurements show it was made in 1971, which coincides with the changes in water pump nipple sizes and the heater valve thread size.
https://classicoldsmobile.com/forums...estion-108677/
1970 Supreme operation:
Last edited by Fun71; Apr 21, 2020 at 03:59 PM.
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