I live in AZ and my 98 4.3 blazer is at 130k and still running strong. The A/C wasn't working so I had it checked out and was leaking down to .39kg from the recommended .79 through a bad schrader valve, which was replaced. Now the A/C blows ICE cold in the AM but later on in the day it blows warm and sometimes slightly cool at most. The system is still holding all it's pressure after that valve was replaced. The orifice tube is also clean.

I just replaced a thermostat and swapped all the coolant with the prestone all models all compatible coolant and the engine temps are at factory specs and does not overheat or anything with the a/c on.

Can't figure it out....I would appreciate some suggestions on this.

 

Are you sure it is fully charged, it would not hurt to have it checked again. It may not have been fully charged or could have leaked down again. The unit will ice up and lose it's effectiveness if it has a low coolant charge. When you shut it off do you get an unusual accumulation of water behind the left front tire as it sets for awhile? This can indicate a freeze up in our more humid climates but maybe not yours.When it starts blowing hot again look under the hood at the pipes that go into the plastic air box, you also should not be able to see the fan motor sticking out of this housing. The housing needs to be cut away to change the motor and then replaced to cool properly on the SUV's. I just went through this with mine, not many people know this and maybe the fan was replaced and not reassembled properly.

This advice and a dollar will get you a cup of coffee just about anywhere.

 

Do this FIRST... I think its because its SO hot the system can't cool all the air blowing across the coil. Try turning your fan downandswitching the return setting to Recirculate ( MAXA/C)the and see if you get a teperature drop. If you don't notice a difference... follow Brock's instructions.

 

It is also possible that the condenser isn't able to cool the A/C refrigerant enough and you are hitting the high pressure limit.

If you notice that the compressor is kicking on, then kicking off after running a bit (not very quick cycling, but not staying on constantly), then you may be hitting this limit... This could be resulting from an overcharge or possibly from a clogged condenser... But a clogged condenser usually causes engine cooling system overheating as well...

 

I will definately check everything mentioned and go from there. Thanks for the help so far.

 

Hey, alright someone else from AZ on this forum. If you're in the ever so hot phoenix area (like me) then part of it not working durring the day is the 120* heat, which you would be more than familiar with. What im thinking though is pretty much whats already been said. Either its clogged and shutting down when it heats and expands or its way low and its just crappin out durring the day.

 

The condensor may be clogged up then, but it's definately ice cold in the morning,I can get one cheap, will probably replace the radiator and water pump while i'm at it too as preventative maintenance since I got 130k and original parts.