Electronic Touch HVAC-control unit

[GregorE]

Hi everybody!
My 84 Regal has the mysterious Electronic Touch HVAC-system which works fine except for one issue. (Thanks to all the people who already shared a lot of information here concerning the regular AC-controls. This really helped me locate the problem.)
If I choose a temperature only one step higher than the minimum, the blend door opens completely and lets a lot of hot air flow into the cabin. (I watched the little motor move the short arm that opens the door. It’s located right behind the glove box just like the mechanical unit/cable from the non-electronic version.)
If I choose the minimum temperature, the blend door closes completely (just like the heater valve in the engine compartment).

Did someone here experience the same problem?
Does anyone know more about this option?
Does anybody know how to inspect and repair the control unit? (I’m quite sure that it’s an issue caused by this device.)

Thanks

 

[GregorE]

Forgot to explain that the blend door does not change position when I choose any higher temperature. It’s either completely closed or opened.

 

[salvageV6]

http://onefootinthegrave.net/filez!/warez!/trservice/enhcdpdf/sec06-a.pdf

Pages 8A-68-5-8 has the tests you need to do on the electronics, could also be the thermistor temp. sensor as described in the tests.

 

[salvageV6]

Try ths link for the full manual.

Electronically Linked and Searchable Manual

Section 8A.

 

[GregorE]

Try ths link for the full manual.

Electronically Linked and Searchable Manual

Section 8A.

This will help a lot, thank you!

 

[GNVenom]

I built a tester many years ago for diagnosing the control head and blower module. Haven't used it in years though.

If a power transistor fails, it could cause your issue. Other component failures, like capacitors, can cause similar issues.

But it sounds like either the ambient temp sensor or the cabin temp sensor is faulty, causing the runaway control problem.

 

[GregorE]

Hey everybody!
I'm happy!
Worked throught the manual yesterday and then started with the Ambient Sensor today. This one is placed on the RH below the right wiper.
One of the connections was loose, the second one came right off when I held it in my hands. I guess somebody working on the AC, wipers etc. got stuck an ripped the connections off.
I soldered both cables to the sensor which has the correct resistance of about 5000 ohms and now the Electronic Touch HVAC works perfectly again. What a relief!

Thank you again!

 

[Blacky]

Nice catch!