Forum Discussion

map40's avatar
map40
Explorer
Sep 29, 2014

2006 E450 AC problem - FIXED

So, my AC defaults to defrost when I loose vacuum. I know what you are thinking, the check valve in the vacuum tank. Maybe, but not.
Here is the info:
1) I check the pressure in the black line going to the vacuum manifold and it goes up to 15 psi
2) I added another check valve with vacuum tank
3) I check the pressure with a hand pump and moved all the actuators, no leaks after the manifold

So, as I'm driving and I accelerate, the pressure drops. The check valve does not stop it.
If i disconnect the line to the engine, it WILL STOP LOOSING PRESSURE

So, we tried with the engine on, shutting the engine off and it will loose the pressure within 4 seconds. If I disconected the feed from the engine, it will stop loosing vaccuum, because the check valve would work.
Any help will be greatly appreciated.

ON EDIT - Fixed. I runed a line from the connection by the engine oil fill tube through inside of the fender to a rubber gromit covering a hole right behind the door wire harness. Once inside the cabin I installed a vacuum tank with a check valve. I just router it to the top covered actuators and hook it up to the manifold. No holes to drill, $20 and 20 minutes of work, all it took. I'll see if I can a few pictures.
By the way, a dealer quoted me $900, and AC shop $500.
  • Sounds like the dashboard control for the A.C. is bad and vacuum is leaking past it causing it to default to the defrost mode.
  • riggsp wrote:
    Sounds like the dashboard control for the A.C. is bad and vacuum is leaking past it causing it to default to the defrost mode.


    Thanks for the post. Unfortunatly, not the case. If I disconnect the feed from the engine going into the vacuum manifold and use the hand pump everything work greats. No leaks whatsoever. When I connect the engine feed WITH a check valve, it starts loosing vacuum. If I disconnect it again leaving the check valve, it will stop loosing vacuum.
    Mindbogglingly, isn't it?
  • Only thing left would be the actual fitting the vacuum hose connects to...either the fitting is cracked, or if it screws into the manifold, it's leaking past the threads...hope you find it!