Dash Air

[Smartstream]

Does anybody have a exploded view or diagram of the box in the passenger footwell that houses the A/C evaporator and heater core? I'm trying to sort out the vacuum actuators. I can open the fresh air door at the bottom but am having trouble with the defrost door and heat-A/C door hidden behind the cores. I think one of the actuators is leaking but I'd like to know more about it before ripping the whole thing out. Thanks.

I should add this is on my '87 345.

[Air345Fly]

I do not believe that there are any doors or ducting behind the
A/C evaporator/heater box at the passenger's feet. The box is
flat against the firewall. All of the ducting and valves are under
the dash.

If you pull the instrument panel back you can get access
to what is back there.

[Magnet18]

I could dig up the diagram of my 83 310, but it sounds like it's different and won't be helpful

No vacuum actuators or AC in the passengers footwell in 83

[Smartstream]

This is the unit in the passenger footwell.

Attachment 346720

I have been torturing myself behind the instrument panel for several days. About the only thing I can see is the end of a plenum box.

Attachment 346721

I don't see any possible access short of pulling the glove box or the entire dash.

When I pulled the instrument panel the hose/tubing connection block on the back of the heater/A/C control was disintegrated and the 4 tubes were hanging loose. The black tube appears to be vacuum, the blue tube opens the vent door at the bottom of the footwell, the red I think is the defroster and I assume the white must be some kind of blend door. The blue and red actuators hold a vacuum from my hand pump but the white bleeds down.

In addition to finding the actuator I also have to figure out which of the 7 ports the tubes connect to.

I have a '92 Dodge Cummins that uses the same control. It uses 5 of the 7 vacuum ports where the moho seems to use 4 ports. The Dodge uses the top slide lever to operate a blend door while the moho uses the slide lever to control the water valve. I also have a diagram from the late Wayne that shows a large black vent/recirculate tube. So far I have been unable to locate a large black tube.

Anybody who has any additional info I would appreciate the help. Thanks

[Smartstream]

Don't know why the attachments didn't load, I'll try again.





Seems to have worked this time.

[Air345Fly]

I went through my dash A/C to get it cooling OK. I had to replace
one freon line. It seems OK now but I might have the freon level
too high.


I never chased the air lines down. The back of your dash looks
like mine. I will dive in there when I do some more A/C work.


Here is a picture showing the electrical and vacuum connections
on my A/C control switch. Hope this helps.

[Smartstream]

Originally Posted by Air345Fly

I went through my dash A/C to get it cooling OK. I had to replace
one freon line. It seems OK now but I might have the freon level
too high.


I never chased the air lines down. The back of your dash looks
like mine. I will dive in there when I do some more A/C work.


Here is a picture showing the electrical and vacuum connections
on my A/C control switch. Hope this helps.
Attachment 346734

Thanks, that is a great picture and the same part number as mine. I have a blue tube that opens the door below the heater core in the footwell. Is that it hiding on the left side in the bottom row opposite the red tube? I've blown up the picture and I think I see a hint of blue but am not sure. Thanks

[bobmiller1]

The blue vacuum line runs through the lower heater/ ac box from underneath the right front wheel well. They are known for breaking. That door controls the recirculating feature of the climate control, which pulls air through the (box) from inside the motor home rather than outside. The mechanical cable that shuts off the water flow to the heater control valve is a crappy system. Any hot water at all that creeps past that valve into the heater core will negate any AC at all. Best to either replace the heater control valve with a manual ball valve or buy an electrically operated heater control valve that has a positive (off). The black plastic vacuum line runs from a black plastic ball (vacuum reservoir) usually mounted on the upper firewall outside to the climate control selector on the dash. It is fed vacuum by a rubber hose mounted on the intake manifold, it is also equipped with an internal check valve so that the vacuum operated doors do not move during acceleration. Regards, Bob

[Air345Fly]

Here is a shot from the other side of the A/C control;

[Air345Fly]

Bob mentioned the heater water control valve. My valve is operational
but I don't know is it will work properly in actual use on the road.
Since you are in there you may want to lubricate the cable.

Here is a trick from my motorcycle days long ago. Poke the cable
end through a hole in the bottom of a plastic bag. Clamp the bag
to the cable using a tightly wrapped rubber band. Put a little heavy
oil in the bag and hold it up so the oil runs down the inside of the
cable. I generally let it sit for a few hours. Eventually the oil
will come out the other end.

Wipe up the mess and the cable will slide much more easily.

[Smartstream]

Originally Posted by bobmiller1

The blue vacuum line runs through the lower heater/ ac box from underneath the right front wheel well. They are known for breaking. That door controls the recirculating feature of the climate control, which pulls air through the (box) from inside the motor home rather than outside. The mechanical cable that shuts off the water flow to the heater control valve is a crappy system. Any hot water at all that creeps past that valve into the heater core will negate any AC at all. Best to either replace the heater control valve with a manual ball valve or buy an electrically operated heater control valve that has a positive (off). The black plastic vacuum line runs from a black plastic ball (vacuum reservoir) usually mounted on the upper firewall outside to the climate control selector on the dash. It is fed vacuum by a rubber hose mounted on the intake manifold, it is also equipped with an internal check valve so that the vacuum operated doors do not move during acceleration. Regards, Bob

Is this the door you are talking about?



I haven't found where the blue tubing enters the box but that door hinges forward when I apply vacuum to the blue tube with a hand pump and the vacuum holds. This is the only door I can actually see.

The cable controlled valve is intact and free but I have no idea how well it stops the water flow. I do have a manual ball valve in the hose so water flow can be shut off manually in hot weather.

This is a Cummins diesel so the vacuum set up is different. Part of the problem is this system is totally different set up than my 280. The 280 has the evaporator under the center of the dash and the heater core in the footwell. All the ducting is under the dash. The 345 has both heater core and evaporator in the foot well and ducting under the dash and forward of the firewall. I've been through pretty much everything in the 280 system but with the differences in the 345 I was hoping to find some decent diagrams before I got in too deep. Having the Cummins also adds potential differences. Again thanks for the help. Every bit adds to the learning experience.

[Smartstream]

Originally Posted by Air345Fly

Bob mentioned the heater water control valve. My valve is operational
but I don't know is it will work properly in actual use on the road.
Since you are in there you may want to lubricate the cable.

Here is a trick from my motorcycle days long ago. Poke the cable
end through a hole in the bottom of a plastic bag. Clamp the bag
to the cable using a tightly wrapped rubber band. Put a little heavy
oil in the bag and hold it up so the oil runs down the inside of the
cable. I generally let it sit for a few hours. Eventually the oil
will come out the other end.

Wipe up the mess and the cable will slide much more easily.
Attachment 346779

Funny you should mention that. The cable was stuck and the dash end was bent. I was able to straighten it and get it freed up. My oil bag is currently hanging on it and last I checked there is oil dripping out of the other end. It is one of those simple, inexpensive solutions that actually works. Thanks

[Smartstream]

Originally Posted by Air345Fly

Here is a shot from the other side of the A/C control;
Attachment 346778

Thanks, yes that is the view I needed.