Automotive Air Conditioning Information Forum

Hot under the collar that is. I need help.

20107 Ram 1500 3.6.
Checked the R1234YF pt table and i was a bit over charged. Adjusted PSI but no improvement.


Here is my issue and fustration.

Vent blows at 47 degrees on the road, hign noon in the sun, high fan and system recirculate.
If I lower the fan speed the vent temp does not change.

So why is it when im driving in 90+ Degree weather in the morning i get 47 Degrees and on my return trip at night
with the ambient air at 80 and no sun traveling same roads and speeeds the vent temp goes UP to 51?
Should it not be going down?

Is that a 2017 RAM, and are you sure that it takes R-1234yf? Does the under-hood decal specify that? My reference sources say 23 ounces net weight of R-134a, and 6.0 fluid ounces of PAG-46.

Regardless, let's start off with the correct amount of refrigerant, precisely weighed into a well-held vacuum, before trying to diagnose the system.

Post the high-side and low-side pressures (after recharging) at about 1,800 RPM and maximum heat load on the system (doors and windows open, A/C on Max, blower on Medium or High). Also post the center vent temperatures and ambient temperature.

This OE compressor appears to be a variable-displacement type with an electronic control valve, so you won't get proper testing results unless the system is under maximum heat load on a day that's about 90°F or above.

Are the fans in the engine compartment working?

yes 2017 with R1234yf.

low psi is 48
high is 210

With a low side of 48 PSI with R-1234yf, the evaporator is going to be operating around 50°F when it should normalize at ~30 PSI on a 90°F-plus day, corresponding to an evaporator temperature of about 33°F. The 48 PSI/50°F reading obviously isn't cool enough to provide a center vent temperature of ~40°F on the aforementioned hot day, along with a comfortable cabin.

The high side of 210 PSI seems a bit low at 90°F-plus.

My guess is that the refrigerant charge is "off", the control valve on the variable-displacement compressor isn't functioning correctly, or both.