Jrzvetteman

I have a 1991 l98 coupe. I recently had the ac converted to r134a. before the conversion it did not work so i have no previous experience with performance. Since i had it converted and filled it is poor performance. air is cool sometimes, and i noticed compressor cycles on and off alot. could this be my problem since freon may not be pressurized?? I cleaned evaporator and condensor with little change in cooling. Im reading between 72-80 on middle vent in 100 degree weather. ANy help would be appreciated because c4s are HOT, especially with glass top

oldalaskaman

quick cycle usually indicates low freon, you should take it back and ask them to recheck it.

JackDidley

Need to get a pressure gage on it. Should be below 50° at the vent even if its near 100° outside.

engle1147

If compressor cycles on and off alot and there is no/low condesnation on the accumulator and vent temps are up then you've got something going on there that isn't correct. Compressor short cycle is usually a condition of low freon levels. You should be able to use a AC manifold gauge to get a better idea of what is going on.

I run the same 134a converted compressor as your yourself but on an '89 'vette. My 134A converted system @ idle or otherwise pretty much ejects ice cubes (with vent temps of mid to lower 50's) when outside temps are below 90 F. Once outside temps are in the mid 90's (95 - 99) things are a very different story...@ idle (under drive pulleys) vent temps are right at 65-70 F but once the RPMs come up (normal driving) vent temps will fall to low 60's.
134A in most converted applications will struggle with achieving low vent temperatures once temps hit +95 F.

Jrzvetteman

thanks for the suggestions i will have to buy a gauge set and go from there ive read a clogged orifice tube or dryer could also cause the on off cycling how would i check those out without evacing system

engle1147

If you have a clog in the system it will be pretty obvious when looking at the hi/low pressures (you'll need an AC manifold gauge set for this).
Other than using a manifold gauge set to view the pressures (interpretation)there is really no way to get into a system to check into things without doing an evac and disassembly. System pressure switches can/will/should disengauge the compressor's clutch to prevent damage should the internal pressures get too low/high.