I'm looking to replace the low side pressure switch on an 87 305 carb. The listed part number for the switch is 3041336, but everything I'm seeing online says this thing only clicks on at 45 PSI which is the kick on pressure for R12, but my system has been converted to R-134A so I'm thinking I need a different or specialized switch so 45 is nearly in the yellow for an R-134A system. Can anyone offer some guidance on this? Specifically, I'm looking at something like this:

https://www.gmpartsdirect.com/oem-pa...c=YT1wb250aWFj

Thanks!

 

The pressures, and consequently the requirements for the switch, aren't THAT MUCH different. The OE one generally works fine in a conversion application. The purpose of the switch, in spite of the name, isn't so much to "cycle" the clutch, as it is to protect against freezing up.

 

Most of them can be adjusted through use of a flathead screw adjusted with it still installed. Disconnect the plug wire and look under it for the screw. I think the only difference is the setting it comes preadjusted too. They usually print it on the switch body. Hook up a Guage and adjust to your preference, but last time I checked there wasn't much difference between the R12 / R134 settings. Autozone sells both.
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It makes a signifigant difference adjusting the switch when airflow across the condenser is good and the engine has a little rpm in it. Years ago the only change to my G-van was adjusting the stock R12 switch. Dropped the cutout down to the point the R134a pressure/temperature curve shows for 32°F. On the open road on a 105°F day the converted R12 system would get down to 40°F at the vents. Prior to adjusting the switch the best it would get to is about 55°F. HUGE difference in comfort.

 

Do you remember what you set it at? I have a couple old converted systems that I need to tweak. Guess I could just do trial and error if necessary though.