A/C pressure switch problem(i think)

[Ryann]

I recently evac'd and charged a '91 16v car that had a dealer 134a conversion sticker on the strut tower with 32oz (as indicated on the sticker) and high and low side pressures were both through the roof, continually bouncing off of the high limit switch with the aux. fan wired for high speed.

Evac'd and recharged to 16oz and pressures were closer to normal but still not quite right, suction a little low and discharge a little high. Vent temps were decent.

[markt51]

Ok so yesterday i got the system charged pretty close or right at 28-30oz. Pressures were still in the 38-40psi for low side, i lost the adapter for the high side, so i havent gotten a reading for that yet, but i would assume its good.

I think i figured out why the switch isn't working. Its because the little metal pin, that opens the schrader valve on the dryer, isn't long enough. I removed the o-ring from the shrader valve and put the switch back on, no leaking at all, which means to me means its not long enough to open the valve to get the pressure. Oh and i used a wrench to tighten it down more, which did nothing.

EDIT: yea with mine at about 15oz it worked, but just wasn't cold enough. Now that its full, it seemed pretty cold when i first charged it to 30oz but now doesnt seem as cold, idk probably just me though.

[mrgraphics]

Yes this is an old thread, but when doing this conversion, this is probably the one thing that will drive you crazy. Indeed, when you get the dryer canister, and one of these pressure sensors, ultimately it never fully depresses the valve to measure pressure when you screw it down. You'll wonder why your compressor doesn't kick on . . .maddening.

I took a solder iron, and made a small ball, then let it drop on a flat surface. I made it a little smaller than the opening of the valve so that air could still get past. The dome of the drop served to touch the sensor at just the top, allowing maximum air flow. Then when I tightened it all down, I heard a little "hisssss" then nothing as the seal engaged. Perfect.