2005 ford 450 hvac vaccuum leak?

[hilcntry]

Greetings!
I've been to a couple RV and Ford boards and remember someone with a similar problem. He said the vacuum reservoir was replaced to clear his problem. My take is that all cabin air is directed through the heater core no matter where the hvac controls are set. Before engine has reached operating temp, all is normal. Once the engine has reached operating temp, (heater core now hot) outside air or AC air is much warmer than it should be. Any advice on checking vacuum motors appreciated, or am I on the wrong track.

2005 Ford F450

tia
hilcntry

[j-d]

Welcome to RV.net!

This RV.net Thread will get you through it.

Yes, add a new vacuum canister and check valve. You can do with just a vacuum line, but the A/C will divert to Defrost on acceleration or a grade.

This BATauto.com Thread has more detail, and illustrates how much unneeded work I went to before determining the problem was buried in HVAC cabinet.

Easiest thing: Buy a 6-ft lenghth of Vacuum Hose. Cut the black tubing after the connection to red under the hood. Cut the black tubing in the passenger kick area. My pics show both. Connect from the connection at red and the cut piece inside that goes UP into the dash. Run engine at idle. All A/C modes should work. If so, there's no need to mess with instrument cluster bezel, passenger knee pad, etc etc. Just install a vacuum tank and check valve, fish vacuum hose down inside fender to door post, connect and you are done. Give due credit to ACME Company and it's Road Runner Bomb.

[hilcntry]

Greetings!


Sorry for confusing you all. The vehicle is an E450 repeat E450.
not an F.

hilcntry

[Hemi_RT]

No the air isn't routed through the heater core before it gets to the different stages (for a better word. There is a blend door before the heater core which directs the air to where ever you set the controls, whether it be heat, vent (outside air) or A/C, adding heat redirects the blend door and heater shut off to start to open so some air goes through the heater core thus warming the air if requested. You'll have to look under the dash and watch which door is moving when you operate the controls. You may not see all the doors/vacuum motors as some may be inside the housing. I'll try and dig up the schematic for you vehicle.