Vacuum Line for Heater/AC Flap Control

[Fuzz15]

Have 2001 Winnebago Adventurer on F53 Ford Chassis and the flaps stopped working' stuck on defrost . The vacuum canister is not receiving any air. Any suggestions on next step? Tks

[Hikerdogs]

Which vacuum container are you referring to. There are 2 canisters. The most likely culprit is the sphere shaped canister under the hood. It's centered left to to right above and in front of the radiator. You'll probably have to stick you head inside the hood and look up to find it. There should be a small blue plastic line and a larger black rubber line going to it.


Many times the blue line gets knocked off when someone checks the oil level. It's close to the dipstick and can be knocked off without realizing it.


The other main vacuum canister is below the right headlight. It's a rectangular box attached to a frame member about 6" x 8". There should be a rear facing plug with 2 or 3 lines in it. The plug has a couple "latches" to keep it in place.


If both of these units are in good shape and connected it's time to remove the engine cover and check for rodent damage. Mice and other varmints love to chew on the rubber lines especially if the have gotten road salt splashed on them.

[Fuzz15]

Tks for your reply. The sphere canister has two black hoses one small one which goes to the switch and the other goes to the side of the engine. Started the engine and no air comes out of the black hose from the side of the engine. Physically challenged to get under the chassis to check where it is connected to the engine, so will have someone check this out. Located the other canister behind the headlight and can only see the blue electrical wire to it. Again will need someone to check as the vacuum hose(s) on top which you cannot see unless you crawl under. Tks again and will let you know the outcome. Let me know if any other areas I could check.

[Waiter21]

Most (if not all) automotive systems are designed that if the controller fails, it will fail to the defrost position.

You may have an "Evans" system. ON mine, I found the vacuum line on the accumulator had been pulled off. During my research, I also heard of the vacuum lines being cut, melted.

Here is a link to my problem, in that article you'll find links to Evans who has some very good diagrams and troubleshooting charts.

Heater A/C blows Defrost mode, regardless of switch setting | 2001 Coachmen Mirada 300QB

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[Hikerdogs]

You don't need to get under the coach to check the vacuum lines going to the canister by the radiator. You can take off the engine cover from inside the coach. It's usually held in place by a latch on the rear side that takes an allen wrench. The latch is usually just off center left to right and about an inch or so off the floor. You will probably have to feel for the socket head since the carpeting on the housing will cover it.


On our 2001 Winnebago Adventurer this was the only thing securing the cover in place. On our 2013 there are also a couple chrome plated screws in the lower front corners that have to be removed. Once the cover is off you can easily see almost all the vacuum lines going to and coming from the engine.

[Johndale]

i think everyone needs a copy of this.


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[Johndale]

Ok got my new control switch in and had to trim the tab off as shown. Note to self compare two switches to match. Nothing here move on 😳
Had toads a check valve just before the accumulator someone removed the old one and system works great. The system will hold vacuum for 2 minutes after shutdown. I saw one issue though. The flapper actuator is kind of worn out. When it pulls it twist in the bracket. Nuts are tight. $90 for that unit.


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