L31MaxExpress
I'm Awesome
Sounds like the cycling switch may be cutting out too early. I have seen numerous examples of the stock switch start cutting out the compressor as early as 60 psi and cooling drastically suffers. Change the switch and the systems will go right back to cooling correctly. I carried a spare stock switch in the glovebox of my Express van for years as it failed more than once. Then I found the R134a thread older style adjustable switch. That switch is still living over 10 years later. I would fit it with an adjustable switch myself and dial it in to cutout just before the evaporator core freezes into a solid block of ice. I checked the 87 G20 van the other day and the cycling switch is cutting the compressor at 18 psi on it. 18 psi is equivalent to the refrigerant boiling at 25F. R134a would need to cutout at 21 psi in theory. R152a has nearly 2x the latent heat of evaporation of R134a requiring substantially less refrigerant to do the same work in the evaporator core.I have the factory coolant diverter valve that seem to be working. My issue comes in specifically at speed. 2krpm in the city is around 4* C colder than 2k rpm on the highway. I get instant couple of degrees of temp drop idling slowing down to less than 45mph off the highway exit.
Four Seasons 36496 is the R134a thread adjustable switch and it is calibrated at 22 psi out of the box. OE application includes a 1994 G10/20/30 van. 37219 is the connector replacement for that switch.
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