Panel Heater/Vent Control

TruAmerican · 12-20-2019, 10:34 AM

I have a 2004 Sightseer 35N. I switch the control knob from vent to floor to mix to defrost and it does not change. I get defrost only. Is it a fuse or in the directional valve or what? Any help is appreciated.

Bones2003 · 12-20-2019, 11:45 AM

That system uses engine vacuum to control the dash heat/air mixing system. Go to www.evanstempcon.com and look for their diagnostic guides - great info if you want to troubleshoot it yourself. You can also search various forums because there is a lot of information out there on this exact problem. I had the same problem on my 2003 Itasca Sunova caused by mice chewing through a vacuum hose.

Morich · 12-20-2019, 12:08 PM

Bears checking but my first thought would be checking the vacuum tubes. Default when they go bad is often the defrost. Also the rubber type tube is prone to getting brittle and cracking or falling off.

TruAmerican · 12-21-2019, 11:03 AM

Bones and Morch---Thank you so much for this information. I have had three responses and all say it is probably the vacuum line. I will check this out when I pull the cover before our trip. This is why I love this site; everyone is so helpful. Thanks again.

Morich · 12-21-2019, 12:41 PM

Keep in mind that some of this is pretty close to wild guessing!!
But wild guesses do still have value. But before pulling the cover, there may be an even easier way to start. Depends on the total layout but some engines and covers work out so that one can get a look at several of the vacuum lines by looking under the hood. If the ones you see are dry and tend to crack when you squeeze or move them, it may be time to just go for replacing much of them as a pre-trouble deal. Vacuum lines are used for all kinds of operations and some of them will cause engine problems if they go open.
I hate to spend money too quickly but I do like to buy cheap stuff line tubing and replace them when convenient, rather than set on the side of the road and wonder.
Good luck and hoping it is an easy one to spot.
Many times there is a manifold where several lines connect together. Manifold is just a way to say a gizmo with several openings. So if you have the engine running and pull one tube off, you can stick a finger over the end and feel for a slight vacuum. If no vacuum there, start tracing back toward the engine as that is where the vacuum is developed. You probably don't have an old enough unit but on older, the vacuum fed the windshield wipers. One line breaking meant several really important things stopped.

EDIT: In trying to follow the link above, I found there may be a change in ownership and possible this is a better/newer link?
https://www.proairllc.com/design-eng...empcon-guides/
Troubleshooting for your specific trouble?
https://www.proairllc.com/pub/media/...ting_guide.pdf

Bones2003 · 12-21-2019, 01:08 PM

I think you can get a drawing from the Winnebago support website that shows the connections for all the vacuum lines. They are mostly all up under the dashboard. The drawing number is 169851 or 169852 (depending if it is a Workhorse or Ford chassis). I found an easy way to check mine was to:
1. Start the engine and let it run for a few minutes to build up the vacuum in the vacuum reservoir.
2. Turn off the engine. Since there is a checkvalve in the vacuum line, vacuum should maintain in the reservoir.
3. Trying to keep the kids and dogs quiet, turn the mix knob on the dash heater control through a couple of settings (off, floor, vent, mix, etc..) and listen carefully. You will hear the vacuum motors/actuators opening and closing the mix doors inside the heat/air unit. If you don't hear anything, you have a leak and lost the vacuum needed to run the vacuum motors.

After fixing my leaks, the vacuum actuators continue to move for quite awhile after the engine is shut off when I turn the heater control.

Morich makes a good point. Although a bad vacuum line is a high probability candidate for your problem, there could be 15 other things in that system that are causing your problem.

Bones2003 · 12-21-2019, 01:15 PM

Morich, good catch on the new links for the Evans-Tempcon information. I'll need to update my bookmarks. Thanks!

Morich · 12-22-2019, 09:10 AM

Quote:

Originally Posted by Bones2003

Morich, good catch on the new links for the Evans-Tempcon information. I'll need to update my bookmarks. Thanks!

Seems like everything I learn on the computer is prone to changing when I need it!

NeilV · 12-26-2019, 06:30 AM

Vacuum line problems with these early 2000's coaches is going to become more common as they used very fine hard plastic tubing on them which is prone to breaking down from age especially along the length of the seam were it was extruded.

A very common place for these lines to break down is under the hood where they go across to the AC unit with another common failure point being where the attach to the vacuum reservoir tanks behind the front bumper where either the plastic line has failed or the rubber transitional has failed. Any place heat, sunlight can get to them or they can be subject to movement (such as under the hinged dash) or vibration can be a trouble spot. The act of opening the dash or touching them once they have started to degrade can cause them to fail as now that they are over 10 years old even though they may look shiny and new they can be quite brittle.

The lines can be spliced with rubber vacuum hose or windshield washer tubing and the plastic line itself can be bought in 6 to 10 foot lengths at most auto parts stores but will most likely only be available in black unless you special order it.

jimkamery · 01-02-2020, 10:29 AM

My reservoir developed a leak and of course it is not a job any of us would like to tackle pulling the heater and ac core to get at the reservoir. The easier solution was to just cut the line in the engine compartment that goes to the reservoir and pull a new line from the engine compartment through the firewall to the area above the passengers feet. I bought a generic reservoir and check valve on Amazon and installed it and all is good. There are several good websites on doing this modification to the Ford E-series and F-series chassis.

TruAmerican · 01-04-2020, 10:55 AM

Thank you for your responses to my issue. You referenced two drawings (169851 and 169852). Could you give me a link to the site for those drawings? I have searched several sites and could not find those drawing. I have several other drawings for vacuum systems but not those particular drawings. Thanks in advance.

Bob

Bones2003 · 01-12-2020, 12:52 PM

Try doing a search for a file named j35z_heating.pdf for the vacuum line drawings.