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1984 S 5 speed. My heater level slide gives me variable and tremendous heat in the last inch of travel. Before that, the temp is the same from the left position all the way to the start of the last inch. What adjustment do I have to make? While the dash was out, all I did was check the diaphrams and hoses which were all air tight. Thank you all.
1984 S 5 speed. My heater level slide gives me variable and tremendous heat in the last inch of travel. Before that, the temp is the same from the left position all the way to the start of the last inch. What adjustment do I have to make? While the dash was out, all I did was check the diaphrams and hoses which were all air tight. Thank you all.
You may have the same issue that my '85 924S does. Missing outside air temp sensor. That's located on the front side of the drivers side fender liner behind the side marker. There should be a flexible tube running from the alternator cooling intake up to that sensor. Apparently the thermostat only has off (all the way left) and wide open heat (just a notch to the right) as defalt if that sensor is inoperative.
The temp slider manages a variable resistance used to determine the target temperature in the cabin. I don't have a control head in front of me to share the actual connection points for testing or the expected values. The important thing is that there needs to be a connection that varies consistently across the full span of lever motion. If you are familiar with using the Ohm meter function in a simple DMM, you'll be able to find if this is the cause. The HVAC control tead will need to come ut for this testing.
Be aware also that there are limit switches at the extreme ends of travel for that temp slider. Your description of the last inch on the slider being the problem means it's unlikely to be the switch, since the switches are only actuated with the extreme ends of lever travel. You may be able to hear them click as you slide the lever all the way to the ends at cold and hot positions.
Han, I dont ever remember seeing such a sensor.
Dr. Bob, I will wait until you have a chance to guide me further! You are the Doc and Docs orders govern.
Happy New Year to you and the bunch. Thanks for the info!
Han, I dont ever remember seeing such a sensor.
Dr. Bob, I will wait until you have a chance to guide me further! You are the Doc and Docs orders govern.
Happy New Year to you and the bunch. Thanks for the info!
The outside temp sensor is in the alternator cooling hose inside the front wheel well. It's hidden in front of the wheel well liner.
I don't think that it's the issue though.
The symptoms for the outside temp sensor failure are "full cold when all the way left, full hot everywhere else."
You seem to have "full cold until the last inch or so to the right."
I'm very interested in this "fix". I have an 88 S4 with the same symptoms. It makes it very difficult to set the cabin to a comfortable temperature. Either too hot or too cold.
The predominant failure mode for the temp control system is failure of the sensor connections at the left front fender well area under the headlight. The sensor sits in a metal tube that placed in the alternator cooling duct. Failure of that side of the loop means full-hot unless/until the temp slider is in the full-cold position where the little micro-switch "forces" the heater control valve vacuum solenoid to open, and hopefully causes the valve itself to close. Access to the sensor is via the forward wheel-well liner panel. The hose is looped up and back down through a UU bracket that screws through the plastic panel. The wiring to the sensor is unsupported, and over time the motion and the exposure to road crud and water take their toll.
But that's not the issue reported by the OP, based on symptoms.
For Walt's case, the most likely problem is dirt or wear on the resistor strip that's "wiped" when the temp slider is moved. Access to this requires removal of the HVAC controller from the console, disassembly of the controller cover by removing a few screws and prying open the tabs that hold the case halves together. Then carefully clean the wiper and he resistor band it slides on, using electrical contact cleaner. Verify the function of the resistor using a DMM set to measure resistance (Ohms), looking for a smooth change in resistance as the slider is moved end-to-end through its range. Once you've got that, reassemble the covers, and reinstall the controller in the console for a full function check.
The WYAIT list for the controller includes full cleaning, replacement of the bulb (possibly with LED), repair/replacement of any fractured fiber-optic "cables" to the *****, and adding a heavy-duty clutch relay if that hasn't been done already.
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Our favorite vendors offer rebuilt control heads (928 International for sure), and rebuilding/upgrading service is available from Greg Brown. Others may chime in with their offerings. I'll warn you that you want to make the decision to have the head rebuilt --before-- prying the case open and messing with the stuff inside. Several folks shipped controllers to me for the compressor relay "fix", after they'd managed to break light fibers, burn traces off the circuit board, or break the case tabs. If you aren't comfortable with the tools and the procedures involved, do yourself a big favor and have one of our experienced vendors take care of it for you. Mucking around blindly in the controller risks more repairs and more costs to get them fixed.
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Walt, that's the whole treatment protocol. No additional presripshin is needed.
DR. BOB IS THE MAN! Moderators, please dont put that in lower case. I actually took it apart and cleaned it (like every other component when I had the car apart). I didnt think to clean the slides, but did replace the slide ***** and secure the fiber optics. I noticed that there was no light to the slides AFTER reinstalling it. I know what has to be done now. When I do the pod circuit board replacement, I will jump into the heater control and power lock button.
This is the reason for communication. Thank you and have a happy new year (
Could it be?
So while taking the console apart to check what Dr. Bob said and guess what I found? Look at the picture. The prior owner had someone fix a HVAC problem by shorting the two orange wires with a straight pin.....When I removed it, i get heat all the time with the fan off, temperature control set to 65 degrees, and the bottom slide set at any position. I am thinking that I need a new heater control unit.
Well, let me ask you good people if there is an idea concerning the purposeful shorting of the two orange wires? Is the switch N.O or N.C.?
Anyone have a unit for barter?
So your problem is likely with the sensor control loop after all. This is one of the limit switches - they are NO switches. With these shorted together it is as if the slider is either all the way hot or all the way cold all the time (depends which switch it is). These kind of fixes are stupid band aids - you need a real fix to restore function!
As described before - first check the external sensor connections?
Assembled components?
Ok, so one of the first things I did well over a decade ago was to remove the AC compressor and evaporator in front of the radiator (hence, stripped of non-essentials).I did this because I typically dont use AC except in the Cadillac or truck and I wanted to ensure the cool running of the aluminum 928 engine. When I asked about the price for a new block when I bought the car 21 years ago, the dealer told me 30,000 dollars. The parts guy probably was pulling my leg, but I thought about pulling the engine at any price and decided to help the airflow and remove all non-essential (according to me) loading on the engine. So thats why there is no AC system, but would it have any effect on the rest of the system? What I am missing is what is in these pictures, correct?
Hey Walt. Based on your thread, I checked mine. The sensor and hose are mounted on the plastic cover in the drivers side wheel well, in the cavity the headlight rests in. (4) bolts, taken out with an 8mm socket. What is in your picture is what is supposed to be in there. Mine does not look as pretty as the pic tho!
Just to get closure on this thread, I obtained a good head unit that had not been molested and relamped, cleaned and greased it. Also obtained a almost new outside air temp sensor and plumbed it to the alternator. The fan runs faster and the controls give me the air temp selected. Thanks for the advice, you guys sure do know these cars. I will share the knowledge base as is the mission of Rennlist.
12-30-2017, 07:52 AM
Adjustment of heater control slide?
