'94 Lesabre AC compressor cycles on and off continuously. Won't blow cold

[Carnie]

My '94 Lesabre AC compressor continuously cycles on for about 1 second then off for about 5 seconds, then repeat. It does this regardless of the temperature selected on the heater controls. I have tried the full range from 60 to 90deg. AC will not blow cold.
I have also noticed an intermitent condition where the displayed temperature on the heater controls blinks on and off.
Any ideas?

Additional troubleshooting info:
Compressor continues to cycle when the temp probe in front of radiator is unplugged. Compressor stops cycling when the #5A fuse (10Amp - ign/auto AC) is pulled (heater controls are also disabled).

[brcidd]

Both symptoms you describe point to an extreme loss of refrigerant- due to a leak- most likely leak location for your make and model is the compressor shaft seal and compressor body o-rings- look for oil/greasy residue about the front of the compressor- and oil sling path on radiator hose and any other nearby objects... The a/c display flashing means a code is set- in your case it probably is the low charge code- and it will turn the compressor off- tosave it from burning up from lack of lubrication- from such a small amount of refrigerant in the system. Find and fix your leak- evacuate and recharge is what needs to be done at this point.

[Carnie]

Thanks for the reply.
AC compressor stopped cycling and behaved after adding a can of R-134a. I will examin further for leaks.
I was a little thrown by the fact that the AC compressor tried to come on even when the heater cotrols were set for max hot. Any ideas why it does that?

[brcidd]

It is designed that way-- all climate control designs will dehumidify the air before heating it- this is supposed to be the "ultimate" in climate control protocol....the only way to disable the compressor is to hit your "econ" button- if you dislike the compressor running with heat request....Manual a/c systems do not do this... so you have the upscale version.....

[imidazol97]

Originally Posted by Carnie

Thanks for the reply.
AC compressor stopped cycling and behaved after adding a can of R-134a. I will examin further for leaks.
I was a little thrown by the fact that the AC compressor tried to come on even when the heater cotrols were set for max hot. Any ideas why it does that?

bricidd is right. The compressor runs unless you push the "vent" button which uses outside air without the compressor running the AC pump
OR the outside temp drops below 50 to 45 degrees and then it turns off to protect the system from running when it's too cold.

Using the "vent" saves gasoline unless you need the humidity control. Try driving with it normal and with the "vent" pushed. When the defrost button is pushed, it always tries to run the compressor unless outside temp is below 45-50.
AND the compressor tries to run in Recirculate setting also, again unless the outside temp is too low.

[Carnie]

Well, learn something everyday, I guess.
Thanks for the responses. Very educational.
-Carnie

[brcidd]

The exact value of the outside ambient air temp cut-off for the compressor is 40 degf - so the compressor does not run when your ext temp display reads lower than 40.....

[DarkerMaster]

I had a similar problem several months ago...turned out to be the shaft seal, and i had to get a new compressor(not a bad price though). Still the best suggestion I can make is, if you have to flush the system completely or even slightly (and i am sorry for the caps) ADD OIL BACK TO THE SYSTEM, if you forget to do this you will more than likly burn the seals on the compressor.

the only problem I am still having is that the AC display will not stop flashing anymore, and it will blow hot (heated, not just uncooled) air until it begins to flash. I have no Idea what is causing it...any help?