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Topic: In Dash HVAC Duct Selector Kaput (Read 1570 times) previous topic - next topic

Re: In Dash HVAC Duct Selector Kaput

Reply #21 –
Quote from: craneman –
when the step is down what covers the box opening on a 2003?


OEM on a 2003 is either a single air step that extends like a platform or a Kwikee 2-step Series 22 (IIRC) electric swing down model.  There is no box opening.

Re: In Dash HVAC Duct Selector Kaput

Reply #22 –
Quote from: Michelle –
OEM on a 2003 is either a single air step that extends like a platform or a Kwikee 2-step Series 22 (IIRC) electric swing down model.  There is no box opening.

That complicates the issue on advice I was giving. I guess you have to access the box from underneath the coach after all.

Re: In Dash HVAC Duct Selector Kaput

Reply #23 –
I can't see too well up close.  Are there 4  screws
that hold the mounting flanges?

Re: In Dash HVAC Duct Selector Kaput

Reply #24 –
Quote from: Traveling Man –
I can't see too well up close.  Are there 4  screws
that hold the mounting flanges?

Yes, but you need to make sure the problem is at the vacuum generator. You could have a broken vacuum line in the dash or another issue leaking the vacuum. I used a vacuum gauge tool that pulled vacuum on the line coming out of the can to the dash and made sure it had no leaks. If you look at the post I did you can see the tool. If you don't have anyway to test that the hvac vacuum system is good. You might be wasting your time on the vacuum generator, it could be good. If you can get air pressure up over 100 psi. and take the line off the vacuum can to the dash see if there is vacuum coming out of the port on the can. If so the generator is working.

Re: In Dash HVAC Duct Selector Kaput

Reply #25 –
I'm speaking to other future readers as well as the original post. At some point after you diagnose the vacuum problem you may discover that your electric vacuum pump doesn't work and a replacement is really expensive and no more durable than the one Foretravel used when they built your coach. If you look at your air brakes diagram you may notice that some older models of your coach used an air powered vacuum pump shown there on the diagram. Those air powered vacuum pumps are just a venturi with no moving parts. They're very inexpensive ,should last forever, and use very little air. The diagram probably shows a "safety" (60 psi check valve) and perhaps a solenoid valve that opens when the ignition switch is turned on. I don't feel like digging out my diagram right now unless someone finds this information useful, in which case please say so and I'll do a little research. When my expensive electric vacuum pump dies again I'm putting an air powered pump in for a permanent replacement. I'll probably use an automobile air conditioning service type vacuum pump designed for evacuating the AC system before charging it with refrigerant. I haven't actually done this so proceed at your own risk. Someone on this forum found an air powered vacuum pump from an older Foretravel and installed it in their coach a while back and it worked great. I forget who it was but maybe they'll write in and say where they found it.

Re: In Dash HVAC Duct Selector Kaput

Reply #26 –
Quote from: RRadio –
I'm speaking to other future readers as well as the original post. At some point after you diagnose the vacuum problem you may discover that your electric vacuum pump doesn't work and a replacement is really expensive and no more durable than the one Foretravel used when they built your coach. If you look at your air brakes diagram you may notice that some older models of your coach used an air powered vacuum pump shown there on the diagram. Those air powered vacuum pumps are just a venturi with no moving parts. They're very inexpensive ,should last forever, and use very little air. The diagram probably shows a "safety" (60 psi check valve) and perhaps a solenoid valve that opens when the ignition switch is turned on. I don't feel like digging out my diagram right now unless someone finds this information useful, in which case please say so and I'll do a little research. When my expensive electric vacuum pump dies again I'm putting an air powered pump in for a permanent replacement. I'll probably use an automobile air conditioning service type vacuum pump designed for evacuating the AC system before charging it with refrigerant. I haven't actually done this so proceed at your own risk. Someone on this forum found an air powered vacuum pump from an older Foretravel and installed it in their coach a while back and it worked great. I forget who it was but maybe they'll write in and say where they found it.
My '99 still uses it and I posted a thread about repairing it "obsolete vacuum generator" There are also posts about cheap vacuum pumps around $50 to replace vacuum generators.

Re: In Dash HVAC Duct Selector Kaput

Reply #27 –
Quote from: craneman –
If you can get air pressure up over 100 psi. and take the line off the vacuum can to the dash see if there is vacuum coming out of the port on the can. If so the generator is working.


C-man,
Pulled that line off  yesterday ............Nada.

Re: In Dash HVAC Duct Selector Kaput

Reply #28 –
I'm presently online via wifi which seems reliable.

If I can hear air escaping from inside the black box
then I would say that the problem is there and not further down the line.  When the vacuum line from the canister to the dash is disconnected there is no vacuum.

Re: In Dash HVAC Duct Selector Kaput

Reply #29 –
I guess a broken vacuum line in the box could be the problem. My problem was not the same, the air never stopped but I had vacuum. Without a check valve as soon as the vacuum switch shut off the solenoid the vacuum would leak out through the generator. Without proper tools to check vacuum it is a tough job. There is a tool called Mighty Vac that maybe Auto Zone or O'Reilly's will loan out. Hook it up to the line to the dash, pull vacuum and see if it holds. If it does you are good from the vacuum canister to the dash. Opening the box up would be something you can do for a visual. 4 screws held mine down and other fasteners held the cover on.

Re: In Dash HVAC Duct Selector Kaput

Reply #30 –
I was able to get the black box off and removed 2 screws from the back that seated into the air line
fitting.  But in order to get the cover off I think the fitting itself has to be taken apart as it encapsulates
the side of the box.

I did get a peek inside and it looks like it could be a pump rather than a venturi.  However all the plastic pieces are milky white and not black like any pictures I have seen.

Before I took it off the only time I could hear a leak was when the HVAC was turned on. After I R&R'd it,
it leaked even with the ignition off, so I disconnected the weather-tight connector and it quit.

I didn't dare mess with the air line fitting for fear of having an unstoppable leak,  so for now I have the connector ends taped up, and no apparent leak anywhere. 

Afterthought;  I have never heard anything running like a vacuum pump, and with air lines running to the box it must be a venturi rig?




Re: In Dash HVAC Duct Selector Kaput

Reply #31 –
If it has an air line it is a venturi vacuum generator. The power to the solenoid to let the air pass was activated by my ignition and HVAC I was able to lift the cover off without breaking anything. I can't remember exactly but I think there was a nut on the air fitting I took off.

Re: In Dash HVAC Duct Selector Kaput

Reply #32 –
I didn't feel like the box was coming apart without
taking the fitting apart first.  My eyes aren't great but the fitting looked and felt smooth with no wrench flats.

When the venturi generator is working properly the
air from the system is always exhausting through it whenever the key is on and the HVAC is on, creating an open drain?

There is also an adjustable air pressure valve that is probably set to where best vacuum and least amount of air loss are?

Thanks C-Man.

Re: In Dash HVAC Duct Selector Kaput

Reply #33 –
Quote from: Traveling Man –
I didn't feel like the box was coming apart without
taking the fitting apart first.  My eyes aren't great but the fitting looked and felt smooth with no wrench flats.

When the venturi generator is working properly the
air from the system is always exhausting through it whenever the key is on and the HVAC is on, creating an open drain?

There is also an adjustable air pressure valve that is probably set to where best vacuum and least amount of air loss are?

Thanks C-Man.

There is a vacuum switch that shuts off the air solenoid after vacuum is achieved. You can see it in the post I did.

Re: In Dash HVAC Duct Selector Kaput

Reply #34 –
Quote from: craneman –
There is a vacuum switch that shuts off the air solenoid after vacuum is achieved. You can see it in the post I did.

I understand,  thank you.

One more thing. ........... why does my air solenoid stay open whether the ignition switch is on or off,
and only close when unplugged? Sticking relay?

Re: In Dash HVAC Duct Selector Kaput

Reply #35 –
It shouldn't. The power comes to the vacuum switch then to the solenoid from the HVAC which I am guessing is only live with the ignition on. Back tracing the power should find out what is feeding it.