E450 A/C Cuts Out on Mountain Climbs—Vacuum Issue or Normal?

[msrdo]

We are still learning this magical mystery machine. Have travelled with the group's input from MS to lower Cal and now up to Wy near Yellowstone. Been a great ride! I have a question though as to the expected performance of the engine systems in the mountains. I have noticed that at altitude... say above 4-5000 feet, when I accelerate to climb and the transmission downshifts, I lose A/C. It seems the A/C valves cause diversion of the airflow to the windshield. I assume the increase in altitude affects the capability for vacuum and thus causes the A/C diversion valves to change. A/C promptly returns when the hill is topped and the transmission downshifts. It has been consistent, so I assume expected, or is there a vacuum issue? Sorry for the newbie questions, but thanks in advance!

 

[bikendan]

Moved thread from the General Tech and Repair section to the Motorhome section's Forester and Sunseeker sub-forum for better help from other Forester owners and possible factory support.
Also because the issues are related to the motorhome chassis.

 

[Chuck_S]

As you suspect this is a chassis issue -- Ford -- not a Forest River issue. Local Ford truck shop probably has a cure although those in Mississippi will have little experience with high altitude issues so check out there in Montana before you go home. Cursory web search turned up:

The AC system on your ... E 450 is designed to divert to defrost when the system loses vacuum and this a pretty common problem on your E450. The common cause for this is in most cases due to a leaking vacuum storage reservoir that is located inside the evaporator case and in most cases, replacing it will resolve this problem for you.

-- Chuck

 

[msrdo]

Thanks.

 

[Chuck_S]

Several more suggestions are listed in "Similar threads" below. Not sure if they were there before. The forum seems to have a very helpful algorithm that links these.