Maintenance

Hate to see this so often and respond to an old thread but few understand how a GM AC of the 80s works.

First the DA6 compressor (early cars) was flawed from the start, Replacement is an HR (Harrison redesign) 6.

Are two levels of warnings:

- low refrigerant - can add more

- very low refrigerant - compressor is off - usually need to disconnect negative lead on battery to clear.

OK any time the compressor is opened for replacement, I flush and replace with R134A. By this time most have already been converted.

- to properly convert usually means replacement of compressor, dryer, oriface tube (white), O'rings, flush, and compatible oil. Missing any usually means going back in again. I then pull about a 50 micron vacuum and leave overnight to remove any moisture evaporates) and leave overnight to make sure are no leaks.

With a "very low" the system is usually empty and needs a full charge. Once negative side of battery is R&Red and before starting car add a can of refrigerant. This will bring the static pressure up to about 50 psi. Can then start engine in auto and add more to suit (usually about a can and 3/4 for R134A and an Allante or Reatta (same HVAC system) compressor should keep running.

- I generally use a 24" shop fan in front of the rad to keep high side pressures from going to the moon.

When done I like so see 35-45F at the outlet on high max cool.

Being a Floridian all of my cars have AC and all work.

If it's starting to blow cold air add additional Freon with the A/c set to auto fan on hi and temp 60. Add Freon until the compressor runs constantly. If you not getting cold air you will need to take it to a pro and have the system evacuated and checked for leaks. The pressure sensors for the R-12 Freon require a little more R-134a will usually fix the problem. If you do have to take it somewhere for repairs. Advise the tech on how to clear the A/c code.


Ross Longo

Thanks so much for all the advice. I finally got the compressor to run, but it runs for 3 seconds and then shuts off and repeats the cycle. R134 pressure seems OK (in green zone) so I still think it might be a faulty component. Frustrating to say the least

Scott you have to clear the BCM code to get the compressor to run.

step 1 Key on engine not running enter diagnostics by pressing the red and off buttons on the a/c controls hold them in for 5 seconds and you will be in the diagnostics mode

# 2 press the lo fan speed control to skip the codes. The Dic will read ECM.

# 3 press the lo fan speed button again. the Dic will display BCM. At this point press the Hi fan speed control to select BCM. Then press the lo speed button until clear BCM codes displays in the DIC. Then press the Hi button again. The display will read BCM codes clear.

Not clearing the code will prevent the compressor from operating.

press reset or turn the key off to exit diagnostics .

Cross your fingers and start the car.



Ross Longo

Scott, There are many other issues that it could be. Get a good air guy to check it out. Bad connection; bad orfacile, bad dryer, bad switch, etc. etc.

Thanks Warren. I'll give that a try to clear the codes. But it does look like I have an AC compressor issue, since it is not turning on even after I refilled the AC coolant.

Scott, Johnny is telling you to click on "Troubleshooting" on this website, then click on Diagnostic codes and go all the way down to "How to clear codes". This site has it all. Good luck.

its in trouble shooting or untill you learn, just disconnect the battery

Since I just got the car, I'm not sure how to clear the code

you will need to clear the code to get it to work then add just a little more 134 because our sensors do not like 134 less pressure. So try to fill if it works see how long add dye

Computer keeps reporting A/C coolant low as well as A/C compressor off. Can the compressor issue be solved by adding more Freon, or does it sound like I'm going to need a new compressor. It's a 92 Allante