How much force to move heater valve?

[CJHenderson]

I have broken two heater core air flaps when setting my adjustment for the flap. I'm estimating approximately 5Lb of pressure to move the valve back and forth. As for the flaps, the first one was on the car when I got it had a crack on the flap itself, and the second one was new from SLS. I'm not too keen on gambling on the third one.

[WRe]

Hi,
which seal do you use in the heater valve? If it's an O-ring, then you have to use more force than with an X-ring.
...WRe

[CJHenderson]

I received my O-rings from SLS, which I suspected to be the reason for the valve be that tight. Yesterday I placed an order with Authentic Classic and hoping that I get the x-rings that you have on your post.

[thelews]

Moves easier when hot.  When I open or close the heater valve from the dash lever when the car is cold, I make sure to apply pressure at the base of the lever (gently) and a couple of fingers on the rounded portion to help along.  Mine are original, colored and translucent, and I sure don't want to break them and haven't in 17 years. Like I said, when warm it moves quite willingly.