New to this forum. Have a '93 940 wagon-non turbo. The dial control does not seem to direct the air to where you adjust it to. Same air no matter where you turn the dial. Is it controlled by engine vacum? Also, no temp changes. I installed a new heater valve but can't tell if it's working--no heat change at all. The vacum hose is connected to it. Can it be fixed or does a dealer have to do it? Might be a vacum hose somewhere else on the dial control?
Also, the speedometer and odometer stopped working. Is this year model wagon run by sensors or by a spedo cable? Can it be fixed without the dealer. I read that the speedo cluster assmbly is controlled by electronics and not a speedo cable. lastly, The gas gauge stops moving at 1/2 tank. Replaced the pump/sender unit about 3 years ago. Any thoughts on this problem? Thanks

 

Make sure that one way valve is OK, the one under the hood, a plastic vacuum line leads to it and it is between the intake manifold and the firewall. The valve looks like a spinning top, usually black and white, plastic... Blow into it, only one way should pass air. If that doesn't help, most like it's the controller, the actual unit with all the *****. That can be opened and repaired, the break in the Circuit Board is usually apparent. New they are pricey, but cheap in junk yards...

Electric speedo-no cable. '93 usually are much better than '91-'92 but still. If you have a complete and sudden failure however, look at the rear end pick up wire where the thing gets its signal. It is in the differential, the only wire on there. Make sure it's intact.

Gas gauge 1/2 tank? That's strange! If completely bad it shows empty, it may be stuck... How is the rest of the instrument panel? All lights come on the way they should? These instrument circuit boards often have to be refloated to work or else give all kinds of crazy readings, like the gauge at 1/2. Worst case, the sender has to come out but if it's only 3 yrs old, I'd look at the board/gauge first.

 

Assuming this is a Manual Climate Control unit, like mine.
As lev noted, the check valve is the first place to start (experience and hindsight), it was the problem with my heater woes, but I checked it last!

Anyway, the heater control valve in the heater hose...
The flow arrow should be "up" into the heater core. Have an assistant turn the heat control ****, you should see the vacuum operated valve open and close. You can also pull the black sound barrier from the passenger footwell and observe the movement of the bellcrank on top of the heater plenum when you manipulate the heater controls.
If you pull the heater control unit from the dash, you will see a harness of vacuum lines connecting to the back, one may be loose.
Getting the MCC out is quite a bit of work, as you have to remove the center console and the forward part of the console too because the MCC is "behind" the radio tray brackets.

 

Wait!
Before you pull the dash, check the ABS pickup in the rear differential. I am assuming that the set up is the same as my 92. There is a 2 wire harness that connects to that and the wires wear and break, killing your speedo and odo.
Disconnect the wire, pull it back through the spare tire wheel well and disconnect the other end in the left storage pocket.
Repair the wire harness, seal up tight and reinstall.