Join Date: Jun 2009
Location: Panama City, FL
Re: MAX AC won't stay MAX
Sorry to dredge up the old thread, but it's MY old thread, so there!
Found the problem, not a leak at all. That device I installed in the heater hose is defective, and it's not a heater valve at all, it's a sensor! Its only purpose in life is to prevent the blower from operating, and the floor vents selecting, if the engine is cold, because God knows how Aunt Matilda's feathers would get ruffled if the damn car blew cold air on her feet during the two minutes it takes to warm up!
When cold, this sensor bleeds vacuum from the ventilation system if Floor is selected, and interrupts the electrical circuit for the blower. When the coolant warms up, this thing is supposed to open its vacuum circuit, removing the bleed, and close the electrical circuit, restoring power to the blower. Again, it only interrupts when Floor is selected, but it bleeds just enough vacuum in other settings to cause other weirdness, like losing vacuum to the outside/inside intake door, and eventually the other doors and even the temperature control. The device on mine never gets to the warm setting. And there is coolant flow in the heater hose because I can make it damn hot in the car.
I took the car out on the highway, and over 70 MPH, it actually started blowing hot air through the defroster, even though AC through the vents was selected, and set max cool. Let up off the gas and coast, and as vacuum returned, it blew cold through the vents, and switched to recirculate.
I simply took the vacuum connector off of the sensor (R.H. side of engine, in the heater hose) and capped it with black vinyl tape. I also pulled the elctrical connector from the sensor and jumpered the wires together. System now works perfectly.
If you break one of these as I did, just cap the vacuum hoses and jumper the wires, then couple the water hoses together where the thing was. Good as new. Better, actually.
It has always amazed me how poorly this "automatic" climate control works here in Florida. Apparently they don't get much humidity in Michigan. We want to keep our systems on recirculate, even if we're adding warm air to the temperature blend. Outside air is 90%, and it makes a difference in the car when that damn recirc door closes by itself. Now that I've found the thing, I've half a mind to put a vacuum solenoid on it and fix it to manual control.