The switch that selects which vents the air blows out (dash, floor, defrost, off) is not working. All the air comes out of the defrost vents regardless of the switch position. I have a 98 U320. There is no vacuum container under the step. I've checked that the switch itself is switching 12v correctly. The center console lifts up and there is a big sheet metal box with 10 large air hoses going into it. Before I try to dig into it, can anyone tell me what is likely the problem and how to best get into the box. Thanks.
BJ, I found a wiring diagram for our dash air system and it is attached. The following relates to our dash air system. (Foretravel used many different ones over the years.)
Our model of dash air does not use vacuum to change air deflection 'doors'. It uses 12-v (reversible) stalling motors controlled by DPDT relays, that are controlled by the dash Mode rotary switch.
You will get defrost only if the Defrost motor or relay malfunctions.
I think the relays and motors were in the bottom front of the big metal box, which is accessible by removing the front center vinyl dash.
I remember our center dash was attached to the floor and side panels with wood screws. Pulling up the Audit tank/camera/monitor control wood board will give you better view of the wood screws, all of which come out from within the center dash inside area.
Barry, thanks very much for the diagram. It's really helpful to know what is in there. Jack worked on it from the top and by wiggling and re-seating connectors got some of the vents to work, but not the one that pushes air out the dash. But taking off the doghouse center console is a big enough job to where I don't want to tackle that up here on the Alaska motorcade.
Barry can you post or provide a link toe the SCS manual? Attached is picture of my dataplate on mine (1998 u270)
Krush, The only info I have on our dash air, is the wiring diagram I sent in a previous post.
We had that issue in our '95. Pray that it is the relay and not the motor. I watched Bob Irelan and Alton trace wires in our dash for quite a while to find the culprit. Of course, our wiring had been "creatively" altered by a previous owner. It seems to me that it was rather a bugger to get at, but once identified was not difficult to fix. Our issue WAS the relay, not the motor.