bd0nalds0n

88 S4 Auto. I have been through my climate control system and have replaced all four vacuum pods. The entire system now holds nearly perfect vacuum.

My vacuum solenoids, however, are not receiving the proper electrical signals from the climate control head. Specifically:

1) The only way I can get the (blue) recirc flap to close is to swich the system "off." What are the other conditions that would cause the recirc flap to close? I am thinking about adding a switch so I can open/close the recirc flap at will. I understand that later model cars have a "smog" switch that accomplishes exactly the same function.

2) My comb flap opens when the system is switched to "off," but under no other conditions (e.g., temp slider on max cold, max hot, or anywhere in betwen) does it move. I also noticed that the solenoids seem to be either on or off. For mixing, does the climate control just cycle on and off to open and close the comb flap, as opposed to having a "halfway open" comb flap?

I am also thinking about switching the comb flap. With the comb flap up, it seems to draw a lot more air that was previously directed through the door vents. With the comb flap down, airflow is much more even from the door/center vents.

3) The white (heater control valve) pod closes when the system is "off," but opens when the system is "on," even on max cold. (I have the heater control valve arm disconnected, and the valve pushed to "off" during the summer months as I sort this).

I have tested the internal temperature sensor, and the reistance changes when I blow into the little grate on the console, so I know it works (at least it reponds to temperature changes, anyway).

I can get under the car to test the external temp sensor to make sure its okay too.

Is it reasonable to assume that if the external temp sensor is operational, that the problem lies in the climate control head? Anyone know which pins/areas to test on the climate control head, to make sure that the changing resistance signals at the temperature sensors are making it to the head?

Lastly, assuming it is the head, are there any user servicable parts inside, or for $200+ should I just buy a rebuild unit from 928int'l?

The writeups for the pod changes were very helpful. I would add (but I didn't have the ability to take pictures at the time) that the green (defroster) pod was time consuming to get to (pod and guages have to come out), but once the pod is exposed it was much easier to swap the bladder and reattach it than it was to do the comb flap. The writeups omit the green pod r/r, which seems to imply that it's more intimidating than the others.

Thanks in advance.

bd0nalds0n

Now that I think about it, did I replace five pods? Recirc (blue), Heater Flap (yellow), Defroster (green), Comb (orange), and heater control valve (white)?

2V4V

Brian,

You sound as though you know how to use a volt-ohmmeter, do you know how to work a soldering iron?

If you do, I would suggest resoldering the board in your climate head. This has fixed more than a few cruise control and climate heads. Be careful, and check the microswitches at either end while you're in there.

Do also check the outside temp sensor as well - though they are just lowly thermistors, they have a hard life where they are located.

If you have the manuals, there is a procedure for checking what does what. The wiring diagrams will be helpful in giving you a visual reference point for what switch actually works what solenoid.

HTH,

Greg

bd0nalds0n

Greg:

Thanks for the thoughts about resoldering, I'll give it a try. I noticed on the piece that holds the A/C switch, that one of the wires that causes the seat-belt light to illuminate had broken free from the solder and pulled out from the circuit board completely. I just jammed it back in and the light cycles properly now.

Sadly, I don't have a copy of workshop manuals. I need to work on that.

mounted to the tunnel in the same area are two relays. One of them is the gong for when your lights are on and you open the door, the other one does what? My car only has the gong relay in it, the other relay is missing. Sure would be nice if it had something to do with the heated seats, could be an easy explanation for why mine don't work.

AO

Here's a shot in the dark - it worked for me but then I have an 82. I was experiencing similar problems. I thought it to be either the outside temp sensor or the inside tempsensor, or perhaps the temp slider/"brain". I pulled everything apart. Then someone told me that some of the elec signals pass through a circuit board edge connector directly above the accelerator. I pulled the shelf, got under there and shure as sh!+, the connector was cockeyed. I pressed it on and everything came back to life. Worth a shot. Good luck.