Temperature Door/Programmer

[Chris Kennedy]

Concerning the C68 eletronic AC/Heating system (1989): Are the circuits that are grounded in order to cause the temperature door electric motor to move the temperature door one way or the other to the desired temperature located in the programmer unit or the main (push button) control unit? The factory service manual text and wiring diagrams appear to conflict, and I now think that, in addition to controling vacuum functions, the programmer also controls the ground which switches the electric motor one way or the other depending upon temperature desired. Is this correct?
Thanks,
/s/ Chris Kennedy

 

[ecss]

If you have the Helms manual, it describes how to test the voltage going to the motor that moves the Air Mix door in either direction. (I believe at 75F the door should be in the middle position).

The unit must be in Auto mode to do the test!

Page 8A-68-4 Test A4

At the Air Mix door motor Connector, measure the voltage to ground at Pin D (Tan/Black) wire. Put the ignition switch to run and set the Heater and A/C control to Auto mode. Keep pushing the cool button until the display reads 60F. Now increment the temp. by pushing the Warm button until you reach 90F while monitoring the voltage at terminal D.

Temperature mix door moves from fully open to fully closed as temperature setting is changed from 60F-90F.

Between 6 and 12 volts should be present at terminal D in one direction of valve movement and 0 volts on Pin D when the motor reverses direction.

Now move the test lead and measure the voltage at terminal C (Yellow wire) and ground. Press the Cool button until you reach 60F. Voltage should be between 6-12 volts and 0 volts on Pin C when the motor reverses direction.

If the voltage does not follow the above, replace Heater and A/C Programmer.

Also note if you disconnect the battery and reconnect it, the Air Mix door motor will recalibrate itself to a known position which can take up to 1.5 minutes.

 

[Chris Kennedy]

Thank you very much for this detailed description and reply----this is certainly a much clearer description than the one I was trying to decipher. I will work on this problem and report back.

/s/ Chris Kennedy

If you have the Helms manual, it describes how to test the voltage going to the motor that moves the Air Mix door in either direction. (I believe at 75F the door should be in the middle position).

The unit must be in Auto mode to do the test!

Page 8A-68-4 Test A4

At the Air Mix door motor Connector, measure the voltage to ground at Pin D (Tan/Black) wire. Put the ignition switch to run and set the Heater and A/C control to Auto mode. Keep pushing the cool button until the display reads 60F. Now increment the temp. by pushing the Warm button until you reach 90F while monitoring the voltage at terminal D.

Temperature mix door moves from fully open to fully closed as temperature setting is changed from 60F-90F.

Between 6 and 12 volts should be present at terminal D in one direction of valve movement and 0 volts on Pin D when the motor reverses direction.

Now move the test lead and measure the voltage at terminal C (Yellow wire) and ground. Press the Cool button until you reach 60F. Voltage should be between 6-12 volts and 0 volts on Pin C when the motor reverses direction.

If the voltage does not follow the above, replace Heater and A/C Programmer.

Also note if you disconnect the battery and reconnect it, the Air Mix door motor will recalibrate itself to a known position which can take up to 1.5 minutes.