I need to find a mechanic in SoCal to open my dash and fix the a/c.

 

What's wrong with the AC ? Someone here may be able to help.

 

The compressor works well, the fan is okay, the coolant level is full, but the ducts inside the dash are apparently stuck and cannot redirect the airflow from the heater. Result is a whisper of air only comes out with fan on high.
One mechanic said he did not wish to open the dash for fear of breakage.

 

If it's Electronic, there's not much to take off until you check some things out. Whether it blows through the Heater, A/C vents or Defrost is controlled by vacuum which runs to a Postcard size Processor (Programmer) above and to the right of the accelerator. That's accessed by removing the Driver's side Hush Panel.

Before you do anything, make sure the Blower is working. GM pushes a small amount of air through the Heater (to cool the floor) and Defrost to keep the windshield clear with the A/C on. So jumper the Blower Motor directly to the Battery first and see what it does.

Next, vacuum is supplied to the Programmer from the Intake Plenum next to the Fuel Pressure Regulator Supply. Follow that line over towards the Battery and just past the Distributor, there is a Check Valve. One side of that Valve cuts back behind the Distributor and through the Firewall on the Passenger Side with the ECM harness supplying vacuum to the Programmer. The other side runs to Cruise and then to a tank in the Left Head Light well. Make sure it's all intact and that you can only blow air through the Check Valve in one direction. Make sure the tank can hold 10 inches of vacuum.

Assuming everything checks out, remove the Hush Panel and check the vacuum connection at the Programmer and then the vacuum connections at the 3 Solenoids on the Heater Box. Use a vacuum pump to make sure that each of those solenoids work, but pay attention to the one with the Blue Hose - that's the a/c vents.

If this checks out, it can get tricky - have someone operate the Controls and see if vacuum is supplied on the Blue Line with the a/c on. Then try it for Defrost (usually Pink). If you don't get anything, either the Programmer is toast or there's no signal from the Control Panel. There's no way to tell on the '89, but more often than not, it's the Control Panel Contacts and some have had good success by taking it apart and cleaning them up.

I suggest you try all the other stuff first to try and narrow it down.

 

I stumbled across this thread as I'm looking for answers to my own problem. In my case, I have the electronic Control Head, the compressor works and I can switch between heat/vent/defrost without problem. However, I get only hot air blowing - does the programmer control the air mix? Could a vacuum line be the fault?

 

Yes, among other other things a bad programmer will cause only heat. BUT there are other causes, stuck blend door, bad blend motor, bad control head. Usually, its the programmer.

 

Is there a good source for these programmers? Any idea on cost?