Chassis Air Cond Vacuum lines

[Paul T]

I have six attachments on the back of the A/C switch that selects OFF in the 12 o’clock position, AC in the 10 o’clock position and Max AC in the 9 o’clock position. (Heat settings are on the other side between 1 o’clock and 3 o’clock.)

On the back of this switch are six vacuum line connections, three on the top row and 3 on the bottom row.

I can hear an air leak when I select “Max AC” and that setting is not performing as it should and used to, (low air flow from air outlets). The middle bottom row of vacuum connections has nothing attached to it. For the life of me I cannot find a loose line down in that mess.

Have any of you looked at this arrangement and if so can you give me hint where the line that is not attached to goes to. Maybe if I find that actuator I can identify and trace my missing connection, re=connect it and, cool down so to speak.

Thanks,

[garym114]

If it is Evans Tempcon here are the troubleshooting guides for the different control panels.
Evans Tempcon, Inc

[Jackm]

The middle bottom connection is labeled as the vacuum source (in the documentation). In other words, according to the diagram, this is where a black colored vacuums source hose goes. On my system, the air comes out the defrost vents whenever the dial is switched to the Max AC position. Now I have to climb into that mess as well. Best of luck.

Jack

[Paul T]

Jackm - where did you find the documentation for this switch? The connection in question is black however the switch is getting some source because I can see it affect the two actuators I have found thus far. These vacum lines are sure small compared to those I worked with in my childhood! Mine are easy to confuse with an electrical wire.

[Paul T]

Thanks for the link Garym114. It's nice to wake up to a helping hand. Just wish mine hands were a tiny bit smaller to work on this stuff.

[M&EM]

Paul T
I have had similar issues with my dash ac over the past 8 years. Each time the cause was the same and easy to fix. The vacuum line to the vacuum motor on the passenger side under the dash where the the passengers feet could go was the cause. On my coach the builder used a right angle vacuum hose fitting to attach to that motor. It turns out this fitting can be pushed on too far and block air flow at that right angle bend. This would happen under the rare condition my CP would use a small step stool and pushed forward too hard.

Marty

[Paul T]

Well, after more investigation I think my problem is something simple like M&EM suggest as it intermittent. I checked for the missing vacuum line and have decided it doesn’t exist. The arrangement of the lines on my control valve are different than that pictured on the Evans Tempcon, Inc schematics in that looking at the back of the control valve switch the top three lines right to left are RED BLACK YELLOW. The bottom row left to right from back side is WHITE [not used] BLUE with the center [not used] port capped. I looked all over for the GREEN line and finally found it coupled to the YELLOW in a Y fitting 10 inches from the control valve so it does exist.

Back to the symptoms: Initially, (and after several months of non-use), approximately 90 seconds after changing the selector from AC to MAX AC, airflow from the top face vents would decrease and with that decrease, air flow to defroster vents would increase. In that I could faintly hear air near the control valve when switching I suspect the darn thing just needs more regular exercise like I do. Now, after numerous cycles of this selector control valve I cannot duplicate the problem unless I go first to the MAX AC position with the lowest possible fan setting.

I did see the 90 degree bend connection in two places as M&EM mentioned and suspect the one under the hood where the blue line connects to the actuator is the guilty party. Will let you know as that vacuum motor should control the flapper door that alternates from the fresh outside air setting in the AC position to the recirculation mode in the MAX A/C setting. I’m getting suction in both positions at the intake grill by passengers seat however it is much stronger in the MAX A/C position as one would expect.

And M&EM......................A big thank you!!!!

[garym114]

FYI - Last year my 12v vacuum pump started running continuously because it could not pull a vacuum, even with the suction port blocked off on the little tank. The MH had been in Texas summers and 2 winters in Alaska. I thought the elastomers in the pump were probably dry. I wanted to lube them and what I came up with was nail gun oil. It is made to keep the o-rings lubricated. I pulled the suction and discharge tubes to the vacuum pump, switched the key to acc which started the pump and put some drops of the oil in the suction. Put everything back together and the pump is still going strong. Later I put in a drop in a couple of the vacuum ports on the switch and rotated the switch around to help keep it sealed up.

[Paul T]

Well, I'm back to square one again. First full day of a road trip and the original problem has not changed. Cruiising down the road with switch set on "AC", I select "MAX AC" and 2 to 3 seconds later the airflow to face vents decreases dramatically. It gets diverted to defrosters. So back to the troubleshooting guide I guess.

[UFO Pilot]

The local shop told me that the switch itself on mine is leaking. I ordered a new switch from Victory Climate Controls but haven't installed it yet.

[Sammie]

Quote:

Originally Posted by Paul T Well, I'm back to square one again. First full day of a road trip and the original problem has not changed. Cruiising down the road with switch set on "AC", I select "MAX AC" and 2 to 3 seconds later the airflow to face vents decreases dramatically. It gets diverted to defrosters. So back to the troubleshooting guide I guess.

Paul, Look under your front hood for the vacuum lines and connections to the air conditioner controls. You may find you have a bad connection there. Also here is an old link of a fix on another Winnebago.

vacuum line leak anyone?

Sammie

[Paul T]

Where approximately is the vacuum line attached to the 8.1 engine that feeds the vacuum reservoir for actuation of A/C controls

[UFO Pilot]

Quote:

Originally Posted by Paul T Where approximately is the vacuum line attached to the 8.1 engine that feeds the vacuum reservoir for actuation of A/C controls

The vacuum on my UFO chassis is provided by a 12 volt electric pump. Not sure about front engine setups.

[DAN L]

Quote:

Originally Posted by Paul T Well, after more investigation I think my problem is something simple like M&EM suggest as it intermittent. I checked for the missing vacuum line and have decided it doesn’t exist. The arrangement of the lines on my control valve are different than that pictured on the Evans Tempcon, Inc schematics in that looking at the back of the control valve switch the top three lines right to left are RED BLACK YELLOW. The bottom row left to right from back side is WHITE [not used] BLUE with the center [not used] port capped. I looked all over for the GREEN line and finally found it coupled to the YELLOW in a Y fitting 10 inches from the control valve so it does exist. Back to the symptoms: Initially, (and after several months of non-use), approximately 90 seconds after changing the selector from AC to MAX AC, airflow from the top face vents would decrease and with that decrease, air flow to defroster vents would increase. In that I could faintly hear air near the control valve when switching I suspect the darn thing just needs more regular exercise like I do. Now, after numerous cycles of this selector control valve I cannot duplicate the problem unless I go first to the MAX AC position with the lowest possible fan setting. I did see the 90 degree bend connection in two places as M&EM mentioned and suspect the one under the hood where the blue line connects to the actuator is the guilty party. Will let you know as that vacuum motor should control the flapper door that alternates from the fresh outside air setting in the AC position to the recirculation mode in the MAX A/C setting. I’m getting suction in both positions at the intake grill by passengers seat however it is much stronger in the MAX A/C position as one would expect. And M&EM......................A big thank you!!!!

my blue vacuum line splices into the green vacuum line that goes to the heater control valve approximately 10 inches from the vacuum control switch. the center bottom position on my switch looks to be capped off with a black cap.
i had multiple leaks in these lines that i repaired by splicing with rubber vacuum tubing