Does anyone know which color vacuum line is the supply to the selector switch on 2014 Winnebago 34 vista Ford chassis . I’m only getting defrost only 99.9 % of the time. Once in awhile stopped or going down hill it will come out of the dash briefly
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In the E450s this is a common issue. The vacuum reservoirr under the dash fails and the HVAC does not receive a vacuum when the engine is at mid-thigh throttle. Causing the valves to default to defrost.
On my 2006 E450 the line is black from the engine and red at a connector leading under the dash.
They use plastic vacuum lines and they commonly crack and leak. That also can be a problem.
The default Ford behavior if vacuum is disconnected is to go full defrost. That means you still have some vacuum getting through because engine vacuum is highest idling or especially coasting downhill.
I was wondering if I test the reservoir and it is good , could I run a new line to the back of the dash selector switch…..if I can find which one is the supply
I ran a new vacuum line from the tee on the engine thru to the vacuum manifold under the dash on my class C. You will also need a check valve in the line. Didn't use a reservoir but it still worked.
I usually look for the broken plastic line, cut it and then splice in a piece of vacuum. The 1/4" size I think it is fits snugly over the plastic. Failing that, there's no reason you can't run rubber hose to bypass the suspected problem area, it's what vehicles used for decades. Be sure to buy actual vacuum line, windshield wiper hose (for example) looks the same and might fit but will collapse.
I don't recall the size because I bought my roll of line years and years ago. And since I use it to mostly just do repair splices on Ford plastic lines the roll will likely outlast me.
Check youtube, the ford vacuum reservoir is a common failure, and it's impossible to reach, so the solution is to add a new one and abandon the old reservoir. Easy enough to do if you know what to look for, and how to tell what's happening.
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i had this happen to me when I first got my e450
I was on the road and couldn't fix it properly.
I got a simple check valve ( one input one output ) and installed it in the front engine compartment where a red vacuum line connects to the vacuum source.
This got me running and keeps it on AC 90% of the time.
It will go to defrost if I'm going over 65 MPH which is not often.
It was a cheap and quick fix that I did 3 years ago and I haven't been bothered by it enough to take to time to fix it properly.
Its a shame thou as this has been a problem for decades and yet ford never fixed it.
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