I have an intermittant issue with my 2000 F-150 4.6L (168,000 miles). It is a work truck that spends quite a bit of time in the woods. When I am crawling up or down a hill in first gear, the AC sometimes shuts itself off. Not the fan, rather it starts blowing warm moist air as if someone changed the HVAC switch to the vent position. When I get to the bottom of the hill and shift the the automatic tranny back into drive the AC begins to function normally.

Is there a built in override that cuts out the AC to prevent overheating of the cooling system? Thanks fo the info.

 

Either the compressor is cycling off momentarily when it's under load, or the temperature blend door is broken and it flops around to the heat position when the truck tilts upwards or downwards. I'm betting on the latter though.

 

I believe it is the compressor cutting out. I am not sure why though.