HEATER CONTROL VALVE REPLACEMENT

Heater valves fail in several ways. They can develop a leak that appears on the left floorboard. They can become so stiff that the rod will not stay on or become very hard to turn. They can leak internally and prevent the blockage of flow through the core thus heating the cabin even if the temperature is turned to cool. They can also do the opposite and block flow through the core when the temperature selected is hot. 83 1/2 and 84 models may require a accelerator pedal rod modification/replacement to accommodate the new style black plastic heater valve. Factory replacement valves will be if the newest design and contain information about the pedal interference that you should follow. 92 and newer cars may have a problem with the bypass valve located in the heater hoses in the engine compartment, above the alternator. This valve can block flow to the heater core or develop leaks. It is there to prevent loss of cabin heat at idle, something we do not see a need for if the rest of the cooling system is up to par. When we see a problem with this bypass valve, we simply remove it from the car. You can splice in connectors in its place or better yet replace the heater hoses and it with heater hoses from a earlier car without the valve.

Remove the two coolant hoses going to the valve in the engine compartment. You may drain and flush the cooling system at the same time, or just enough to do the job. Then remove the radio and its basket. Use the u shaped tools with the chain between them or some pieces of old clothes hanger to insert in the wholes at the sides of the radio and just pull it out. Remove the ashtray and the two long screws, either Phillips or Torx 20 holding the dash fascia in. The long screws come up from the bottom of the plastic part of the dash, the one farthest right is a bit of a challenge to find, tucked behind the ashtray bracket. This will allow the fascia to come out far enough to get the rod from the temp selector to the valve off the valve. You do not need to remove the dash or fascia, just pull the fascia out slightly to get the rod off.

Saab 900 79-94 Dash Component Breakdown

When working from underneath the dash and/or through the speaker grill, first remove the Phillips or 25 Torx screw at the far left that holds the floor duct and the insulation up. pull the duct down (it will bend) and get to where you can see the four screws, either 25 Torx or 4 mm Allen's holding the valve to the core. Remove them and then remove the valve through the left speaker.

Do not loose the black cover that goes over the left mounting screws, this prevents the cruise chain from hanging on the screws and must be reinstalled.

Clean the heater core mounting area with a pot scrubber. On the new valve, double check the screws in it and apply either Vaseline or silicon gasket sealer to the o rings to hold them in the grooves for them. Then reinstall the valve, being careful not to disturb the seals. Guide the tubes through the grommet in the firewall for the cooling hoses. Remember that the hose coming from the water pump goes to the top tube on the hot water valve. Reversing them can generate a little heat inside the car when the valve is turned off as the bypasses in the valve allow flow through the core this way.

When you get it all together, don't forget to bleed the air out of the cooling system via the bleeder screw on the thermostat housing when refilling the coolant.

Another Way from Joel Giovanni!

Let us start by saying i am no mechanic...I just got a saab last month. I am mechanically inclined. I bought the heater control valve and installed myself. Unplug the negative lead from the battery so you do not get zapped.

I started by removing the 2 hoses that are lined up one on the top of another in the engine compartment and let the fluid drain. Removed the lower plate under the dash...Then removed the fascia screws, 3 of them very long under the control panel. and the one behind the ashtray. This was after the speaker grille was removed the 2 little screws. From there the fascia came loose..The Radio was a chore to get out, put 4 pieces of straight clothes hanger. And shimmy it out till it comes loose.

From there you can loosen the heating vents under the dash and they come loose with the clips...brass, and the 2 screws. Pull down only the drivers side from there the speaker grille can provide good light if you
set the light on top of it. from there if you lay on your back....and peer up you can see the 4 screws...And loosen one at a time. it is hard to reach in there alot of twisting and turning of the hands and the torx
screwdriver. you have to angle on some but use your hands to stabilize the screwdriver. until they are loose and fall out. If you lose them no worries. The newer unit comes with "O" Rings and new screws. Once it is out pull it out through the speaker grille it is easier that way.

Put the newer unit in through the grille too. and drop it into the holes. Through the fire wall. and make sure it seated oin the copper unit where the pipes run up. Once that is done put the 4 screws in hand tight. So they do not fall out.

Go back to the hoses and make sure they are just set on the outside so there is no slippage. Do not tighten them, yet. From here tighten those screws and make sure the O rings are set im place
before you seat it back in. I opted for a hint i saw on another sight. I used 2 dots of crazy glue the slower drying stuff on each O ring. they did not budge at all and it was a nice fit. Tighten up those screws and make sure they are as tight as you can. Twist and turn and readjust your hands. Try other ways if you are having a time of it getting the torx head to sit. till it feels like it is turning. Now put the fascia back into place and make sure the heater vents are aligned. Make sure the arm connecting to the heater control valve is connected internally...It locks in with a flexiable arm. You will be able to turn it by hand and see the know itself turning on the outside. once you have them all tight. Go back to the hoses and make sure they are tight but not over tight. reconnect the battery.

Once that is done. Look for the thermostat. It is towards the front of the car a brass look thing with a valve with no godly reason there, at least it looks like that. Use an open ended wrench. set it on there in place.

Put the coolant back back in the filler and then run the car. Open the bleeder valve half a turn till green liquid starts spitting out. That is what to expect. Run the engine while filling it up at the same time with the engine running. The valve will now spit and foam. Do this till it is a regular flow with no air bubbles. Look back under the dash make sure it is not leaking while it is running and check the hoses. make sure no leaks...

Once you verify all is tight and not leaking. then put it all back together. This will of course be the easy part of all of this. the heater now for me runs like a charm it does not blow out hot air unless i tell it too. feel