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Later heater valve troubles...


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Blue7500 and I refreshed my heater box today with a new fan and new seals.

While reinstalling the heater control valve, I noticed there is this circular plastic disc that springs up and appears to block flow when the valve is wide open. After we installed the heater box we tried to purge the cooling system or air, but I don't know how effective we were. I did get hot air coming out of the vents eventually but it's been hard to replicate that so far.

My question goes out to those of you who have rebuilt later type heater control valves, what is the plastic disc and is it an issue? I thought that perhaps it is a kind of thermostat to prevent flow through the heater core when the coolant is cold but I honestly have no idea. Maybe the system still has air in in and I need to burp it again.

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FWIW a few years ago my mechanic in Tucson, who's been doing only BMWs for the past 30 yrs., installed a new heater valve in my ' 75, with the flow arrow pointed in the customary correct direction, only to find that it did not work. He reversed the valve so the arrow pointed in the wrong direction and the valve has been working perfectly ever since. Go figure.

Bob Napier

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And I've found more than 2 (ok, I've found 3) installed 'backwards'.

Now, mine is installed forwards and I've never had any trouble with

it, either...



"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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installed backwards was due to the lever on the valve being installed upside down. Since it's much easier when removing/replacing the valve to disconnect the cable lever from the valve than the cable from the lever, it's also easy to install the lever upside down, so that setting the dash control to "hot" gives you cold air, and vice versa.

Ask me how I learned this! I make a sketch now...


'69 Nevada sunroof-Wolfgang-bought new
'73 Sahara sunroof-Ludwig-since '78
'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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