R-12 stock, R-134a if modified, vehicles didn't switch till 1993/1994, some '93s were R-12 and some (like a Chevy Lumina APV) were R-134a
To properly convert an R-12 system to 134a you need to upgrade to a parallel flow condenser coil in the largest size you can stuff in there (if not already equipped) as most R12 systems have serpentine, or tube and fin serial flow condensers.
You also need to modify the low side pressure control, if it is a clutch cycling system you need a new pressure switch, preferably adjustable or if it has a variable displacement compressor you have to adjust the control valve on the compressor, this is because 134a is a few PSI less than R12 at around 32°F and if left as-is your vent temps will be a few degrees warmer as a result.
Since 134a has a lower pressure in the evaporator but a higher pressure in the condenser when compared to 12 the compressor will pump slightly less volume and usually won't cool as well at idle.
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does an 89 toyota pickup have r12 or 134?
Linear Mode
