1971 Cutlass Heater control valve
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Joined: Mar 2013
Posts: 146
From: Charlotte, NC
1971 Cutlass Heater control valve
looking for the correct part #. It seems like to only one I can find is
Thanks
in advance
Four Seasons Heater Control Valve 74602
Which sounds like it's the wrong one. I do have the 3/4 NPT threaded hole in my intake.Thanks
in advance
Registered User
Joined: Feb 2013
Posts: 15,394
From: Phoenix, AZ
It is very easy to check if your car uses a vacuum to close or vacuum to open valve, just pull the vacuum hose off the valve and check which position of the dash slider gives vacuum and which doesn't.
Here's some information from an old post:
https://classicoldsmobile.com/forums...-valve-120656/
From Rock Auto's description of the FOUR SEASONS 74602 heater valve:
Vacuum Closes Non-Bypass Heater Valve
So from the description this valve is the same as the one on my car and matches my car's temperature control operation, so I would suspect it is the same for your car, but I would recommend you check to make sure before you buy.
Here's some information from an old post:
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.
Vacuum Closes Non-Bypass Heater Valve
So from the description this valve is the same as the one on my car and matches my car's temperature control operation, so I would suspect it is the same for your car, but I would recommend you check to make sure before you buy.
Last edited by Fun71; May 21, 2020 at 09:24 PM.
Registered User
Joined: Nov 2008
Posts: 670
From: Glendale, AZ
It appears the threaded inlet in the intake manifold changed between 1970 and 1971. Four seasons shows #74601 for 1970, and # 74602 for 1971, the only difference appears to be the threaded inlet. NAPA also shows part # BK 6601052 for the Balkamp heater valve for 1971.
Registered User
Joined: Feb 2013
Posts: 15,394
From: Phoenix, AZ
The vacuum operation changed along with the thread size as shown by the Four Seasons spec information:
https://www.rockauto.com/en/moreinfo...15459&jsn=2043
74601
Description Vacuum Open
Opening B IN = 0.500
https://www.rockauto.com/en/moreinfo.php?pk=815528
74602
Description Vacuum Closes
Opening B IN = 0.750
https://www.rockauto.com/en/moreinfo...15459&jsn=2043
74601
Description Vacuum Open
Opening B IN = 0.500
https://www.rockauto.com/en/moreinfo.php?pk=815528
74602
Description Vacuum Closes
Opening B IN = 0.750
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