AC does ok in town but on the highway on long trips it will eventually just kind of lose pressure. It will be on the highest setting but just barely blow, even though it is still cold. Any ideas, I know nothing of these systems other than it really stinks not having one. Thanks.

 

on your 96 you should have a on and off switch to shut your ac down,next time it does what you say,less air comming from the vents,just click the ac switch off,the system probably froze up on you,by shutting it of it will thaw out and the air will blow as normal again, then turn the ac back on,cause for freezing are faulty low pressure switch,too much freon,did you add any recently, dirty evaporator or condenser.

 

No service to system since I bought it in 04.

 

My 98 will kind of do the same thing. Work fine just goofing around slow but get out on the highway for 15 minutes and it will stop blowing cold. Turn the air off and wait a few minutes and it will blow cold again. I've checked the temp of the air when it is cold and it will hang around 38F to 40F. It also will only do this on days when the humidity is high and temp is over 90F. Any ideas. It has never had anything added to the a/c since it was built.

 

As I said in my above post,faulty low pressure switch or low on freon or freezing up due to improper cycling of the compressor , dirty evaporator and or condenser.If the proper amount of freon is in the system the compressor will cut in at appox 40 or so lbs and as the comp. is running it will pull down to 25 lbs at which time it will cut out and start the cycle again.If the system has too much freon in it, it wont drop down to 25 lbs and therefore wont cut the comp. off and if it hot out and the comp runs continuasly the system will freeze up. A faulty low pressure switch,(stuck in the closed posistion) will also cause it to not cut out,and then freezing of the system will occur, and of course a faulty low pressure switch could stick in the open posistion and not let the comp. cut in,but not cutting in is not the cause in this case,it is cutting in the comp.Poor circulation of air thru the evaporator and or condenser will also cause it to freeze.When the evaporator under the dash freezes up(forms frost over the fins) then the blower motor cant blow air thru it, and thats what you said,slowly gets less and less,once you shut the AC off the ice thaws off and air then blows thru it again.I you scroll down you'l see another post about AC,it may be on the second page by now but look it up,I posted in that thread also. One more thing, if your fan is on and it gradually moves less air as you go along,( not the fan slowing down, just less air comming out of the vents) then you can bet it is your evaporator freezing up.

 

If it's the evaporator freezing up, it may be dirty. I had one get filthy, the condensation would saturate the dust/dirt, then freeze. The coils are not THAT hard to get at, to wash it out. I would put some plastic down to cover the carpet though, as it takes a long time to dry out.