It takes vacuum to change the airflow vents. Most systems, I suppose for safety reasons, default to defrost when there is no vacuum available. You might try to find a loose vacuum hose "under the hood". Sorry I can't tell you where to look, but maybe someone with a WH chassis will checkin soon. Good luck...
Location: Sarver, PA/Crystal River, FL/Shelocta, PA
Posts: 1,196
Below is a link to the Vacuum and Electrical Diagrams for your dash heating and AC controls. With these diagrams you'll be able to diagnosis and fix your problem.
There are also vacuum lines running to the rear of the dash switch assembly. Check behind the switch to make sure all the vacuum connections are firmly attached.
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Tom and Barb
'07 Winnebago Voyage 35L
Workhorse W22 chassis FMCA 219315
Open hood and look for the green vacuum wire or hose that connects to the valve assembly just to the right of the AC/Heater black plastic box mounted against the fire wall on the left (facing) side of the coach....This green vacuum hose is attached to the valve with a small section of windshield hose....The purpose of this valve is to open the various air passages into the coach vents....When it loses vacuum thru a leak, the control box defualts to defrost only.
You can test the green vacuum line connection by pulling out the green hose and putting your finger over the end...If the vacuum motor stops humming (engine must be on), this is the problem......Replace with a new piece of windshield hose....If this is not the problem, start at the vacuum motor and start disconnecting and plugging the rubber lines until it stops running...just follow the lines and plug each joint..good luck...RKL
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Tom N:
Lots of Toms here.