Whats Your AC Vent Temperature??

[Supreme Pizza]

I read something interesting a while back. I tried these suggestions, and the result was surprising. It worked very well. Here is a copy/paste of what I read:

 

"for chevy/gm trucks after 1987 psi recommendations as follows. With an ambient temperature of 70f your low side port psi should be between 32-38 psi. And for every 5degreeincrease in ambient temp your psi readings will increase by 5psi. For optimal cooling it is recommended to use the lower psi. So for ambient temp of 70f, you would achieve the best results at 32-35 psi. the more psi with r134 has the effect of blowing warmer air just as if you where low on refridgerant. so more is not better. you can find your optimum psi easily measuring your vent temp. we have found 32psi with an ambient temp of 70f seems to give the best result. with this setting you can maintain a good cab temp of 32-34f with an outside ambient temp of 70f. And when outside ambient temp is over the 100 degree mark, you can still maintain a chilling cab temp rangeing from 48-52f. remember when your ambient temp (outside temperature ) rises, your psi will rise to."

[Dnt]

bump

[Dnt]

You will note on this P&T chart that at around 35psi pressure the R134A temp is right at 40f 35psi is a typical Low side reading so you should have vent temps in the 40's on a properly functioning auto system at approx 1500 rpm and AC set to max with a lower blower setting.

https://highperformancehvac.com/r-134a-refrigerant-pressure-temperature-chart/

Outside ambient temps will affect a Fixed Orfice tube type AC system more than the Thermal Expansion Valve and Variable Volume compressor systems so you might want to check and see what you have. Also keep in mind that if you have bought a used vehicle there could have been improper service done in the past so you may have your work cut out if you are going behind a Jackleg Shade Tree Mechanic.

YOU HAVE TO READ BOTH LOW AND HIGH SIDE PRESSURES TO DIAGNOSE MODERN SYSTEMS. A proper set of gauges can be had for cheap and then you can do a proper diagnosis plus have a easy way to add refrigerant if needed. There is even a simple vaccum pump that is powered by compressed air for cheap. There is really NO EXCUSE for short cutting on proper AC repair. Lots of threads on here about bad GM condensors that leak refrigerant. The automotive systems hold very little refrigerant you do not have to lose very much to affect performance. If you suspect a problem I would take it to the dealer if still under warranty. If out of warranty I would be either finding a good local Auto AC company or studying up on Auto AC and buying some tools. Just be careful who you listen to for AC repair advice I have seen some really crazy posts on Auto AC repair out on the net that are wrong and misleading.

[myGMC2]

I see the same once the system is cooled off, ~45F