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I was running my AC yesterday and it kept switching back and forth from AC to defrost on it's own. It was about 80 degrees but was extremely humid and I was towing a trailer which made the truck work a little harder but it wasn't under much of a load. Any ideas?
I would say a vacu, leak or bad divertor door actuator.(going to defrost is the default when loss of vacuum occurs)
Look behind the glove box for door actuator.
chk the vacuum lines that go to the solenoid that operates the front 4x4 hubs.
The next question is why did the AC work fine last night (about 9 hours later). I failed to mention that before. It was much cooler then and much less humid but it seemed to work fine then. After the initial problem yesterday morning, it worked fine. Beats me!
According to my Ford dealer, that condition is designed into the Ex and other super duty trucks. Had same issue pulling a larger boat on a hilly stretch of interstate. Was hot, humid and AC intermittence became frustrating. Seems the Ex under heavy load will suspend AC operation for power and resume AC when on flat, downhill, or cooler. Seldom ever pull heavy so this condition is rarely a problem. Still question the wisdom of that bit of Ford engineering.
This morning, when I started my '05 X, the HVAC controls began going haywire. I have the automatic HVAC and it was switching back and forth between low fan, high fan, AC, defrost, etc. The OFF button does not function and turning the fan down turns it up high and puts the defrost on. I see by earlier posts that it could be a vacuum leak. My X was parked so there was no load. Where should I look? MY X is still under warranty but I'd rather not take it in if it's just a loose vacuum hose...Thanks