No heat control- Please Help....... UPDATE April 21
04-16-2011, 11:38 AM
#31
Rennlist Member
Rennlist Site Sponsor
Go to your local lumber store and buy a 10' 1"x12" board. Have them cut it in half. Get a small quantity of 1 3/4" sheet-rock screws and a small bottle of yellow wood glue.
Cut one of the boards to the same height as the door sill of your car. Glue and screw it to the remaining long board to make an "L". Use the remaining short scraps to make braces to hold the L securely.
Put a pad of some kind (a small bathroom rug works well) over the door sill to prevent damage and lay the board on the door sill. Use another rug to pad the board if you want more comfort. Lay down on the board, using your feet to steady the board if necessary.
Much more comfortable working under the dash!
Cut one of the boards to the same height as the door sill of your car. Glue and screw it to the remaining long board to make an "L". Use the remaining short scraps to make braces to hold the L securely.
Put a pad of some kind (a small bathroom rug works well) over the door sill to prevent damage and lay the board on the door sill. Use another rug to pad the board if you want more comfort. Lay down on the board, using your feet to steady the board if necessary.
Much more comfortable working under the dash!
04-16-2011, 12:29 PM
#32
"The most common problem for full heat and no control is an open circuit of the outside
temperature sensor. A test of the sensor at its location (generally near the alternator)
doesn't assure that it's properly connected to the servo unit."
As stated above, it's not the sensor that's usually the problem. It's usually the
a connection problem in the harness from the sensor. A simple resistance test
will check for this.
"I believe the mixing motor has failed giving constant full heat."
A simple power test would easily verify the functionality! But then again, if one continues
to randomly replace parts, when the next CCU problem occurs one can always eliminate
those parts as being bad.
temperature sensor. A test of the sensor at its location (generally near the alternator)
doesn't assure that it's properly connected to the servo unit."
As stated above, it's not the sensor that's usually the problem. It's usually the
a connection problem in the harness from the sensor. A simple resistance test
will check for this.
"I believe the mixing motor has failed giving constant full heat."
A simple power test would easily verify the functionality! But then again, if one continues
to randomly replace parts, when the next CCU problem occurs one can always eliminate
those parts as being bad.
04-16-2011, 12:35 PM
#33
Rennlist
Basic Site Sponsor
Basic Site Sponsor
I also got a control unit that had been just rebuilt back for testing...not sure if this one was yours, or not. This one came from a Porsche dealership. It was good, of course (they all get throughly tested, before they leave). I'd guess that this car also has a bad setting motor.
__________________
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
greg brown
714 879 9072
GregBBRD@aol.com
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
04-16-2011, 01:20 PM
#34
Maybe rebuilders need to sell a 928 complete climate control kit to include
the CCU, the servo unit, and also the water valve & "throw-in" the outside
temp sensor for good measure. That way the 928 owner doesn't really need
to do any real troubleshooting
the CCU, the servo unit, and also the water valve & "throw-in" the outside
temp sensor for good measure. That way the 928 owner doesn't really need
to do any real troubleshooting
04-16-2011, 06:55 PM
#35
Rennlist Member
Thread Starter
"The most common problem for full heat and no control is an open circuit of the outside
temperature sensor. A test of the sensor at its location (generally near the alternator)
doesn't assure that it's properly connected to the servo unit."
As stated above, it's not the sensor that's usually the problem. It's usually the
a connection problem in the harness from the sensor. A simple resistance test
will check for this. What is your test proceudure for this?I followed Wally's tips
"I believe the mixing motor has failed giving constant full heat."
A simple power test would easily verify the functionality! But then again, if one continues
to randomly replace parts, when the next CCU problem occurs one can always eliminate
those parts as being bad.
temperature sensor. A test of the sensor at its location (generally near the alternator)
doesn't assure that it's properly connected to the servo unit."
As stated above, it's not the sensor that's usually the problem. It's usually the
a connection problem in the harness from the sensor. A simple resistance test
will check for this. What is your test proceudure for this?I followed Wally's tips
"I believe the mixing motor has failed giving constant full heat."
A simple power test would easily verify the functionality! But then again, if one continues
to randomly replace parts, when the next CCU problem occurs one can always eliminate
those parts as being bad.
04-16-2011, 08:36 PM
#36
Testing of the 928 Climate Control Servo Unit
1. Place the unit on a bench with the control arm facing up and away
from you, i.e. The 12 pin connector should be pointing toward you.
The 10 connector should be pointing to your right.
2. The pin orientation of the 12 pin connector is with pin 1 to the farthest right.
When looking closely, you'll notice that pins 3 & 4 are one contiguous pin.
Those pins (3 & 4) are ground.
3. The second pin from the far left is pin 11 and that's the power pin (+12V).
4. The first far left pin is pin 12 and that's the control pin.
Before powering the unit, notice where the arm is:
a. at about the 10:00 a clock position (fully CCW) is where full heat occurs
and results from when the control pin is 'open' or if the outside temp sensor
input is 'open'.
b. when the arm is fully CW (about 2:00 a clock) is where full A.C. occurs,
i.e. This occurs when the CCU micro-switch closes at the lowest temp setting.
So to test the unit:
1. Power pin 11 and ground pin 3 or 4.
2. With pin 12 open, the arm moves fully CCW.
3. With pin 12 grounded, the arm moves fully CW.
Note: Sometimes the motor inside gets stuck and one needs to open the
cover under the arm and power the motor directly both ways, i.e. by reversing
the polarity as it moves to free it up. Some light oil is advisable too. This is
done with the circuit board REMOVED, so only the motor pins are fully
accessable and are ONLY being powered.
1. Place the unit on a bench with the control arm facing up and away
from you, i.e. The 12 pin connector should be pointing toward you.
The 10 connector should be pointing to your right.
2. The pin orientation of the 12 pin connector is with pin 1 to the farthest right.
When looking closely, you'll notice that pins 3 & 4 are one contiguous pin.
Those pins (3 & 4) are ground.
3. The second pin from the far left is pin 11 and that's the power pin (+12V).
4. The first far left pin is pin 12 and that's the control pin.
Before powering the unit, notice where the arm is:
a. at about the 10:00 a clock position (fully CCW) is where full heat occurs
and results from when the control pin is 'open' or if the outside temp sensor
input is 'open'.
b. when the arm is fully CW (about 2:00 a clock) is where full A.C. occurs,
i.e. This occurs when the CCU micro-switch closes at the lowest temp setting.
So to test the unit:
1. Power pin 11 and ground pin 3 or 4.
2. With pin 12 open, the arm moves fully CCW.
3. With pin 12 grounded, the arm moves fully CW.
Note: Sometimes the motor inside gets stuck and one needs to open the
cover under the arm and power the motor directly both ways, i.e. by reversing
the polarity as it moves to free it up. Some light oil is advisable too. This is
done with the circuit board REMOVED, so only the motor pins are fully
accessable and are ONLY being powered.
04-16-2011, 08:58 PM
#37
Rennlist Member
Thread Starter
Great, Thanks, shall try to power unit and see.
Wally, you may want to add this to your 'Tips'
Wally, you may want to add this to your 'Tips'
Testing of the 928 Climate Control Servo Unit
1. Place the unit on a bench with the control arm facing up and away
from you, i.e. The 12 pin connector should be pointing toward you.
The 10 connector should be pointing to your right.
2. The pin orientation of the 12 pin connector is with pin 1 to the farthest right.
When looking closely, you'll notice that pins 3 & 4 are one contiguous pin.
Those pins (3 & 4) are ground.
3. The second pin from the far left is pin 11 and that's the power pin (+12V).
4. The first far left pin is pin 12 and that's the control pin.
Before powering the unit, notice where the arm is:
a. at about the 10:00 a clock position (fully CCW) is where full heat occurs
and results from when the control pin is 'open' or if the outside temp sensor
input is 'open'.
b. when the arm is fully CW (about 2:00 a clock) is where full A.C. occurs,
i.e. This occurs when the CCU micro-switch closes at the lowest temp setting.
So to test the unit:
1. Power pin 11 and ground pin 3 or 4.
2. With pin 12 open, the arm moves fully CCW.
3. With pin 12 grounded, the arm moves fully CW.
Note: Sometimes the motor inside gets stuck and one needs to open the
cover under the arm and power the motor directly both ways, i.e. by reversing
the polarity as it moves to free it up. Some light oil is advisable too. This is
done with the circuit board REMOVED, so only the motor pins are fully
accessable and are ONLY being powered.
1. Place the unit on a bench with the control arm facing up and away
from you, i.e. The 12 pin connector should be pointing toward you.
The 10 connector should be pointing to your right.
2. The pin orientation of the 12 pin connector is with pin 1 to the farthest right.
When looking closely, you'll notice that pins 3 & 4 are one contiguous pin.
Those pins (3 & 4) are ground.
3. The second pin from the far left is pin 11 and that's the power pin (+12V).
4. The first far left pin is pin 12 and that's the control pin.
Before powering the unit, notice where the arm is:
a. at about the 10:00 a clock position (fully CCW) is where full heat occurs
and results from when the control pin is 'open' or if the outside temp sensor
input is 'open'.
b. when the arm is fully CW (about 2:00 a clock) is where full A.C. occurs,
i.e. This occurs when the CCU micro-switch closes at the lowest temp setting.
So to test the unit:
1. Power pin 11 and ground pin 3 or 4.
2. With pin 12 open, the arm moves fully CCW.
3. With pin 12 grounded, the arm moves fully CW.
Note: Sometimes the motor inside gets stuck and one needs to open the
cover under the arm and power the motor directly both ways, i.e. by reversing
the polarity as it moves to free it up. Some light oil is advisable too. This is
done with the circuit board REMOVED, so only the motor pins are fully
accessable and are ONLY being powered.
04-19-2011, 11:03 AM
#38
Rennlist Member
Thread Starter
I replaced motor and the arm moves with temp slider. I only had a chance to check if any different from origianl motor.
I would highly recommend others to check "setting motor" functionality with another motor or Lorenfb Testing of the 928 Climate Control Servo Unit procedure.
I would highly recommend others to check "setting motor" functionality with another motor or Lorenfb Testing of the 928 Climate Control Servo Unit procedure.
04-21-2011, 05:32 PM
#40
Congrats, glad it's working out.
