1987 auto heater controller - a few questions

[avale]

Hello, I have a 1987 with the automatic heater controller. My last time using the car, I noticed that the heat was on no matter what I set the controls to. I checked the heat valve and it moved pretty freely by hand but was opened somewhat at rest. Changing the setting on the auto heater controller didn't cause the heat valve to move.

I looked inside the auto heater controller and found the cable disconnected. It appears there is a clip for the ball socket that is missing. I found another post that stated that John Walker said the replacement part is: 999-168-021-40-M100


The cable appears to be wedged/stuck. Can someone tell me where the cable is suppose to be?


In order to help others out, you can remove the rubber boot for the e-brake to peak in and see if your cable is disconnected. If you need to get in there you remove the 4 fasteners, lift up the front of the auto heater control and disconnect the 2 plugs. The controller will rotate up and out of the way.


Oh, I dropped one of the washers and while looking for it, I found this piece under the passenger seat. It appears to be hard rubber or plastic. Anyone know what this is?


BTW, I never found the washer that goes on the fastener that holds the auto heater controller in place. Anyone know the size or part number of that washer?

[avale]

I found this thread very helpful. DIY fixing heater blower. Where to start? I didn't realized that the servo was actually in the top of the auto heater controller cover. So the arm is wedged in there and both sides of the arm are disconnected.

[T77911S]

its been a while since I have been into mine.

first the default position for heat is off. the heater boxes are spring loaded so they open to turn off the heat. take a look and see if they are open or closed. theyshould be completely open for the heat to be off. also make sure your footwell blower motors are off with the heat off. there is a micro switch that goes bad that will keep them on low when the heat is off

you may have to unbolt the Ebrake to get the lever unstuck. also may be a pain as I think there is tension on the Ebrake cable.

I was going to say the arm with the rod on it is upside down but looking at the pic again I am not sure. I do know the rod should be on top and the bottom of the arm is connected to I want to say a bracket that the cable for the heater boxes loops through, as in that cable is just one piece I think. its been a long time since I looked at it. I see a small cable running under the Ebrake and I don't remember that. anyway. if you remove the Ebrake you should see how it works.

there is a cover on the side of the heater controls that you need to pop off. you access that hole to connect the rod to the servo arm. I had my seats out when I did mine so I don't know hard it will be to do with the seat in.

[T77911S]

ok I looked at the PET and it helped a little.
the lever on the Ebrake is oriented correctly but the rod is wrong. the rod goes on the ball on the top of the lever then to the arm on the servo motor.

the cable from the heater boxes has a twist in it (it is only one cable). and a rod hooks to the cable then attaches to the bottom of the lever on the Ebrake.

[avale]

Thanks T77911S! I think I have found the correct parts and once they show up I'll update this thread.

[JK930]

does anyone know who rebuilds these autoheat units
or
has a schematic on the inner workings.

my heat has been backdated to a lever control
but
it would be nice to get it working the way it was intended
thank you

[speednme1]

Originally Posted by JK930

does anyone know who rebuilds these autoheat units
or
has a schematic on the inner workings.

my heat has been backdated to a lever control
but
it would be nice to get it working the way it was intended
thank you

Keep the backdate. Easier to control.

[speednme1]

Originally Posted by avale

Hello, I have a 1987 with the automatic heater controller. My last time using the car, I noticed that the heat was on no matter what I set the controls to. I checked the heat valve and it moved pretty freely by hand but was opened somewhat at rest. Changing the setting on the auto heater controller didn't cause the heat valve to move.

I looked inside the auto heater controller and found the cable disconnected. It appears there is a clip for the ball socket that is missing. I found another post that stated that John Walker said the replacement part is: 999-168-021-40-M100


The cable appears to be wedged/stuck. Can someone tell me where the cable is suppose to be?


In order to help others out, you can remove the rubber boot for the e-brake to peak in and see if your cable is disconnected. If you need to get in there you remove the 4 fasteners, lift up the front of the auto heater control and disconnect the 2 plugs. The controller will rotate up and out of the way.


Oh, I dropped one of the washers and while looking for it, I found this piece under the passenger seat. It appears to be hard rubber or plastic. Anyone know what this is?


BTW, I never found the washer that goes on the fastener that holds the auto heater controller in place. Anyone know the size or part number of that washer?

Connect everything minus the rod and turn your heat on, if the arm goes up on your unit then you only need to replace the plastic ball sockets. You need two of those plastic ball socket tips( I suggest order 4). They should snap right on to the levers and your unit should work as intended. Oh and the little plastic washer looking thing you posted, may be the tip of the original plastic ball socket.

[cpa]

JK930, Contact Kris Rose, JamesDean59@gmail.com He specializes in M-B, BMW electronic repairs. After a few emails he agreed to tackle mine. He did a great job and the price was reasonable.

[avale]

Originally Posted by speednme1

Connect everything minus the rod and turn your heat on, if the arm goes up on your unit then you only need to replace the plastic ball sockets. You need two of those plastic ball socket tips( I suggest order 4). They should snap right on to the levers and your unit should work as intended. Oh and the little plastic washer looking thing you posted, may be the tip of the original plastic ball socket.

I should have indicated that the plastic washer thing is a little larger than in diameter than a quarter. I don't think it has anything to do with the heat controller - I just happened to find it while looking under the passenger seat.

[spyerx]

FWIW, if the rear sensor on the exhaust 'breaks' the heat will go full heat when turning on, no matter the temperature. This sensor checks if the car is warm, if not, it opens the valve all the way until the car warms up.
On my car, the thermo resistor was fried.
I simply jumped the wire at the controller between the seats, so it works now as if the car is warm, always.
The resistor can be replaced but it's a bit of a job to get the old one out and re-rivet the housing back in under the car.

On yours, the control arm broke, just replace it. Turn the car on and it will park itself in the right spot. Make sure your heat boxes are working freely.

[T77911S]

just unplug the temp sensors if they are bad.

when I was testing mine I had all sensors unplugged and it worked fine

[HaroldMHedge]

What you found under the seat may be part of a broken shift rod bushing, 950-424-224-03.

[spyerx]

Originally Posted by T77911S

just unplug the temp sensors if they are bad.

when I was testing mine I had all sensors unplugged and it worked fine

This did not work for mine. When the connection was "open" to the exhaust sensor it opened the valve fully even at 1 and would keep it there. My interior sensor works fine and I didn't try unplugging that. The car actually regulates the temperature pretty nice now.

[T77911S]

just to be clear on our terms.
full heat has the heater box valves closed and the actuator arm in the controls fully rotated. this closes a sw that sends power for the fans to run.

with the EX sensor not connected you will have full heat due to the heater boxes being closed.
(when open the hot air is diverted down and outside the car.)

I did not test it for this but my speculation in how it works is the heat sensor t the heater boxes is only there to "delay" turning on the heat (closing the heater boxes) until the engine or heat is up to temp.
the reason I say this is because if you turn the heat/temp down the fans should still be on but if the arm moves at all the fans will turn off.

[spyerx]

^^^ I think we are saying the same thing. :-)

Meaning: my auto heat was fully functional, except the rear exhaust sensor was "open" (not providing resistance). As a result, when I turned setting to 1, the heat boxes fully direct heat to the cabin, even though fans would be low/med/high depending on dial setting. Meaning, the heat boxes did not vary. When I shorted it, they vary with the dial.

That sensor is there so that on a cold start, it will allow full heat to the cabin, as the car exhaust warms up, it then varies it. Does this to allow quicker cabin heatup.

I think I have a post here where I Showed the process I used, I rigged up a variable resistor to test its function.

[T77911S]

yes,
it just keeps from blowing cold air on you

[avale]

Ok, it took me a while to order the parts and get the time to work on this but I finished it today. You don't have to remove the passenger seat to do this. I added the new sockets to the rod - spaced 118 mm center-to-center of the ball cup sockets. I did drop the motor assembly from the plastic housing (removing the 4 fasteners on the outside) in order to attach the arm to the ball on the motor assembly. There is NO WAY you are going to push this together with your fingers or using a screw driver for leverage. You need to get enough access to squeeze it together with pliers. I hope this helps someone as this site and the people have been incredible for me. Happy to answer questions!

[70tangerine]

Im in search of the rod
Part # 911 659 303 00
My local Porsche shop says its still on back order from Porsche.
Anyone have one for sale ?
I am just now putting more time to find part as 1 year has gone by since we diagnosed the rod is broke. Apparently a common failure.
With mine I can hear the motor working and can see it moving through the Access hole.

[proporsche]

I think you just need the ball joint..i have to look if i still have some..

Ivan