if it is stuck in the heat off position, you could probably not even worry about it, Mine had the spring broken off for probably 20 years, I actually had no idea what it was or what it did, the truck just started and ran so well, I never looked for a problem. Even at 20 below zero, it ran like a champ. The little flapper is hardly a tight seal, and the two parts are bolted together so closely heat transfer is quite good anyway. But if it is in the heat ON position, then you will have trouble. But yes if you feel you really need it to work, Just be patient, you will need patience if you are going to work on these trucks anyway.
