AC Pressure Questions late model R134A conversion

[Kosty23]

Hi all,

I have a 1986 944 that I converted to R134A. I replaced the compressor, TEV, and drier (and the o-rings) I used POE oil.

I put 2 cans of R134A (24 oz) but my pressures still didn't seem right. It took most of a 3rd can to get to the pressures I've uploaded, meaning it should be definitely overfilled.

My vent temps are in the 40s.
Ambient temp was about 80°.

I've attached my readings at idle with the AC on for about 15 minutes.
High side seems to be around what is expected but the low side seems like it should be higher.

I didn't flush the lines, which I'm wondering if I should have.

I pulled the vacuum for 3 hours, let it hold for 45 minutes with no change.

Are my pressures worrisome?

*Edit, photo didn't upload. Pressures are 25 PSI low side, 220 PSI high side*

[originalowner]

The pressures look good based on this website https://ricksfreeautorepairadvice.com/normal-ac-pressures-r-134a-pressure-gauge-readings/

I found an online citation of the factory conversion process that called for 2 and 1/4 lbs of R134A, though I have not seen the TSB myself. Based on this, your fill is close, if slightly high.

High side pressure is highly dependent on ambient temperature and radiator airflow, so not the best measure of fill. The low side pressure you cite is slightly below freezing, but will probably work well as the low side switch has hysterisis above freezing. Adding more refrigerant to get the pressure up to 27 PSIG will prevent freezing of atmospheric water vapor, which blocks airflow on the evaporator coil (the inside part.)

The website above indicates that these measurement should be made not at idle, but at an engine RPM of 1500 RPM. Perhaps, based on the anemic performance and normal operating range of these older cars, 1800 RPM might be a better model of normal operation of the A/C.

[djnolan]

As I recall from the days when I kept my A/C charged, a 2lb R134a charge would get vent temps in the low 40's when highway driving.lb.

The Porsche TSB called for 860 grams or 1.89lb.

http://www.944time.com/porsche/2005images/944_ac.pdf