What's wrong with my A/C in 1993 Toyota Corolla?

Tractor

I have a 1993 Corolla. I've had it for about a year and have used the A/C on and off since then. On days when it was below 85 degrees outside, the A/C would work great and blow cold. On days where it was above 90 degrees or so, it would only blow hot air. It would sometimes blow hot air even when the compressor was in fact on and engaging.































Okay, so I thought it was possibly low on freon which was causing it to work inconsistently. Since it was charged with R12, I decided to have it converted over to R134a. I bought the adapter fittings and the correct amount of freon. I took it to a shop and had them evacuate the R12 and make sure it held vacuum... it passed, so they installed the correct amount of R134a freon. The gauges showed that it was where it was supposed to be and cold A/C was coming from all the vents in the car and the compressor was kicking on as it should. It worked.































However, after 1 day of having cold A/C it starts doing that same thing it did before with the R12. It blows cold A/C inconsistently. Even with the compressor working and kicking on it will sometimes blow warm.































What could be the problem? When I was at the shop the machine showed that it held vacuum as it should and that it was loaded with the correct amount of R134a. If anyone has any info or suggestions, I'd be glad to hear 'em.

Salina Shakya

change it out

mark32937

If you used 75% of the R12 spec weight and know for sure the radiator fan is up to speed, your next step is to get a high side pressure reading. If on a hot day it's under 200 psi this could be a bad expansion valve. If the differential across the compressor is less than 100 it's a bad compressor. R12 oil is not compatible and you are sitting on a sludge time bomb if moisture ever finds a way in there, but after all it is a 93 corolla...