With it out in the open at room temperature it's going to be closed. Put it in the freezer and leave it for a good 15 minutes and if it's good the diaphragm should shrink up and open the valve. Remember this is supposed to call for heat or water flow when the truck is cold. You may have to play with the bias spring adjustment to get it dialed in where you want it. I don't know of any procedure for calibrationg them. These Ranco control valves are marginal at their best so don't expect to have as much temperature control as your new Silverado.
Denny Graham
Sandwich, IL
Last edited by Denny Graham; 02/05/2010 6:59 AM.
