A while ago my AC stopped blowing cold and I put off fixing it until recently. I brought on of those AC Pro recharge bottles to check the level and it turns out my freon was still in the green zone. My AC was converted to R-134 professionally but I think they only vacuumed the R-12 out and changed the nozzle on the accumulator and put the R-134 in.

I read a few old threads that suggested that when your AC blows but blows warm replace the low pressure switch. I brought an R-134 switch (factory air brand) and I replaced the o-ring on the nozzle. However, the new switch would not fit on the nozzle all the way and the valve was still opened to where I could here a hiss. I put the old switch back on.

A friend of mine who is a machinist, measured both switches and said the new one was slightly larger in every way (width and depth) by a thousands. I'm going to return it tomorrow and get the R-12 switch to see if that let's my air blow cold.

Was the accumulator suppose to be replaced when converting to R-134. Do R-134 and R-12 use different accumulators?

 

The accumulator should always be replaced when ever you open the system. The accumulator needs the new desiccant, designed for r134. Be on the look out for that. If the R12 oil (mineral oil) was not flushed, it can clog things in the system as it will find places to settle in the system. GM believes that it will settle in places that will be OK, others, say flush it. I say, why not flush and be on the safe side. There are several reasons why you may be blowing warm air, you first need to get a proper set of guages and hook them up to see what is going on. w/o knowing that, you're shooting in the dark.

What brand of low pressure switch did you buy?

 

The shop who did it, did a budget conversion since they new I was broke at the time. They charged me $112. I'm guessing they brought one of those DIY kits you see next to the AC Pro bottles in the store.

I figured the accumulator was suppose to be replaced. I know they said they flushed it and I do believe them because the owner is a friend of a close friend of the family. He originally said he doesn't like to do it that way but made an exception for me. It was blowing cold until a few months ago.

The brand of the new switch is Factory Air.