I've had my 2000 Ranger 5spd. 4 cylinder for about 3 months now and the AC has worked great. We live in Houston where it's totally flat. We just went to the Texas Hill Country on vacation and noticed at times that the AC and even the air flow from the vents totally cuts off when the truck is going up hills sometimes. It seemed to happen the most in the middle of the day when it's real hot and going up hills seem to be the most consistent time it happened. THen once the truck started down the hill, there would be a rush of cold air that would blow and stay on until the next hill it seemed.

Any idea what's going on here? Thanks in advance for any insight.

 

Does the air move from the center vents to the dash/defroster vents? Sounds like a vacuum situation.

Low vacuum = Climbing hill
High vacuum = Decel down the hill

Vacuum is what controls the vent air position, if there is a fault in it, it will default to the defrost position. So if you have a bad vacuum reservoir or something (not 100% familiar with ford's system), it may be fine all day long at normal driving conditions. But if you start to climb a hill, that vacuum may run low moving them up to defrost.

 

I agree, it sounds like a vacuum problem, since the airflow stops coming out the vents. There is also a WOT (Wide Open Throttle) relay that shuts off the compressor when you are at WOT, but this wouldn't cause the airflow to change.

 

Ahhh...ok. I did a search and saw the WOT relay stuff but I figured it didn't apply here for the same reason you mentioned. I did see vaccuum/defroster default stuff but the other thread seemed to be having an issue with it always going to defrost so I didn't think it applied.

I'll look into the vaccuum issue. I'm not sure if it diverted to the defroster vents or not. I didn't think to check that while it was happening. I'm also not sure I can reproduce the problem in Houston since it's never happened here before. Any suggestions on how I could investigate further without being able to reproduce the problem without hills?

Thanks again for the insight!