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Old 06-21-2018, 02:47 AM   #1
Senior Member
bigben's Avatar
Brand: Thor Motor Coach
Model: Challenger 37TB
State: Kentucky
Posts: 1,029
THOR #1020
AC only blows through defrost vents

We are traveling and I began noticing a problem our automotive air started to blow only through defrost vents. AC was working but would not switch to the vents. Searched a great deal to gain information on what was the cause and then how to repair. The diverter in the fan box is operated by a vacuum actuator on the front. Cause turns out to be almost certainly a vacuum line problem feeding the actuator. Finding the exact vacuum line turns out to be the trick to be able to fix the issue. Turns out the vacuum lines are very numerous and look like spaghetti under the dash. After a great deal of looking, I finally located the problem - the black vacuum line on the battery side of engine compartment apparently had been rubbing against a radiator hose. The vacuum line melted over the course of the last 45k+ miles. I went to my local Auto Zone, bought 3' of 3/16" vacuum line hose, cut out the bad portion and spliced in about 12" of the new line. The old line simply fit inside the 3/16" rubber line. I rerouted the line away from the radiator hose and fastened it loosely in place with an electric tie.

Problem solved -again.

US Army Retired - Loving The Road Trip
Challenger 37TB
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Old 06-21-2018, 11:17 PM   #2
Senior Member
Brand: Thor Motor Coach
Model: Windsport 27K
State: Kentucky
Posts: 729
THOR #2817
Glad that you found the problem and fixed it better than they did at the factory.

Years ago I had a lower radiator hose get cut through by the sharp corner of the frame. I couldn't find a replacement hose unless I waited for a few days for them to order it at a Freightliner service center. I was able to repair it with an old piece of steel exhaust pipe and four hose clamps. From then on it was steel against steel and after I never had a problem with the hose.
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