Hi guys,

My 99 Expedition A/C (front and rear system) is starting to blow a little warm. I'm thinking its a little low on R-134. I have a full set of tools (gages,vac pump,etc) but I can not recall the working pressure on vehicle. Does any one know off hand what the high and low pressure range should be? I will let it cool off outside before working so lets say 92-94deg outside temp. with 75% humidity.

Also is it better to do a full evacuation and fill, or try to top off the system.



Thanks for the help.
Selkirk

 

About 35 PSI on the low side and 200 PSI high side at idle.

If the pressure is low, I would try adding a can first instead of wasting all that is in there. A complete evacuation and refill for a system with rear air is about 4-1/2 cans.