quote:



by **********

my air conditioning stopped working. it was working fine last time I drove and used it. Now, the a/c compressor doesnt activate at all. it blows air when you turn the fan on, but no cold air and the compressor is not coming on at all on Normal or Max setting. I checked all fuses and they seem to be fine.

I checked for power at the a/c unit on the motor but i dont seem to get any 12V+ at any of the wires. (should there be actual 12volts+ on one of the wires while the AC is turned on and running?)

is there an A/C relay that could be bad or a switch? I want to make sure its not a power problem before i conclude that the A/C unit or its clutch is the problem.

one last question, if it was low or empty on freon or  134a, would it stop the A/C from coming on?

quote:

  by Stealth;1340801

The A/C  system will shut down if the system is low in refrigerant.

The A/C compressor is basically a piston in a cyl, just like the car's engine.
if the system is LOW or empty of refrigerant, it may also be LOW or empty on OIL.

Would you run an engine without oil? the A/C compressor needs the same thing, oil for lubrication.

There are different types of A/C compressor oils; PAG, Ester and mineral.   
Which one is your system using?   All are not compatible with both Freon-12 or a R134a.
Something to think about?  What do you have?

The oil may or may not leak out with the escaping refrigerant.  That depends on the circumstances
as to  how it leaked, over what period it leaked, or whether it leaked from the high pressure side
or the low pressure side..

If the compressor does not activate, the cause needs to be found before moving on. 
1. Is the system fully charged? 
2. If it is charged, are the controls of the car providing power/voltage to the clutch?

*** need to know this in sequence as #2 may be a consequence of #1 and
cannot proceed to diagnosis until both #1 & #2 are known***.  

quote:

  by Stealth;1340801

Assuming that you know for a fact that the system is fully charged by having pressure tested
the system both without running  and with the system running, provide the data.

It may be that the compressor is leaking between the high side and the low side.
It may be that the compressor clutches are starting to fail and debri is contaminating the system.
It may be that debri is starting to clog and restrict the orifice and need replacement.
It may be that the drier/accumulator needs attention.
It may be that there is AIR in the system.

The pressure data is needed.

quote:



Determine that the compressor did fail and it is not a system control problem
or a low-refrigerant hut down.  See above.

IF you open the system, you MUST evacuate and contain the refrigerant in the system.
IT IS THE LAW!
Auto parts stores rent or loan the equipment.  REMEMBER, IT IS THE LAW
regardless of it being Freon-12, R-12, or R134a !

If you had an internal compressor failure you need a new compressor,  the o-tube,
accumulator and a very thorough flush or you will have repeat failures. 
Auto parts stores carry A/C flush kits with instructions.

IF you are converting from Freon-12 to R134a, you MUST change all the seals and MUST
FLUSH the sytem well.  Should you not do this, the system WILL FAIL!

After all is installed, torqued and sealed, you need to vaccum the air out of the system.
Auto parts stores rent or lend the vacuum pumps to do the job.

After the vacuum,  add the oil + refrigerant per your car model. requirements. For a
complete fill, expect somewhere between 30 oz to 40 oz of refrigerant, depending on car
and model, to achieve proper pressure on the system.  Most new compressors take the
specialty oil BEFORE you install them.
Again, parts stores may sell or loan or rent the pressure gages.

The only thing that sholud be used is Freon-12 or R134a. 
The use of liquid propane products is not adviced -  the are highly volatile and flamable. 
So is R134a, but to a lesser extent.