2012 GMC Yukon AC + chiller mess

[randeez]

thread resurrection... its a long one, but this is literally the only site that ive ever found that offered meaningful information, and i really appreciate it!

I have recently jumped back onto this project..it got to where it worked ok and i quit messing with it.

currently:
new compressor, packing oil drained and oil added
new condenser, oil added, is in front of radiator - havent specifically cleaned the fins out in a while but I will also try that
new dryer on liquid line to chiller, chiller (heat exchanger) flushed, blown, oil added. TXV could it need to be replaced?
new accumulator on vapor line after cabin evaporator
evaporator was flushed, blown out, oil added.
new fixed orifice tube and holder, just before evaporator
all barrier hoses and oring fittings, nylog blue on orings and threads
system vac'd for roughly an hour, left for 24 hours before charging.
charging with 12oz cans, gauges connected, connect can/flip can, purge line till liquid release, repeated for each can.
electric fans are completely functional and on high speed when ac on.

I only have test ports on the hoses to/from the evaporator, and there is a pressure sensor between the compressor and the condenser that i can see with hptuners.

compressor to condenser, after condenser line immediately splits with a tee - one #6 hose to the dryer>txv>chiller and return line goes back to a tee just before the compressor. the "priority" side of the liquid line tee goes to test port>orifice tube>evaporator>accumulator and back to the tee before compressor.

no solenoids, it goes everywhere all the time.
intercooler pump is pwm controlled so i can adjust flow through it/chiller.

I can, and have, idled for hours and system will cool cabin to 40s at the vent and intercooler coolant into the 40s and have no issues. 90-95° ambient temps (south florida) this is where gauge/port placement skews the info i can see. in either case it works perfect at idle. i havent tried holding rpm at 2000-2500 parked to replicate the same issue as driving, but that may be next step so i can connect gauges and see what low side is doing at that rpm. theres quite a bit of condensation after the orifice tube, on the return hose from the evaporator to accumulator, and even leaving the accumulator to the compressor - which im not sure if thats good or bad?

havent had any "slugging" issues in a long time i would say that have been resolved.

my issue only comes when driving, truck cooling system has upgraded radiator, oem fans for theses are some of the best out there. no overheating problems what so ever will cruise at 200° without ac on.

with ac on 70mph+ puts me about 2100rpm and anything above - the pressure sensor after the compressor starts climbing and after it gets over 270psi or so the ECT starts to climb not rapidly but itll take maybe 15-20minutes before the ect gets to 220+ and thats when i start playing with slowing pump down, slowing blower down and psi will come back down some, but ultimately it will work its way back up. if i turn off ac all together ECT will drop back down within a few minutes.

too much pressure with sustained 2000+rpm, the 270psi doesnt seem all that high but it just seems to start shedding so much heat off the condenser

so tried mechanical fix:
truck is pretty well modified, gears, trans, etc...so cruising it does turn more rpm than stock which would in turn spin the compressor more than normal. so i venture off to try and repulley the compressor or the crank, luckily, I have an aftermarket crank balancer and the ac have a dedicated pulley - called them up to see if they had any options to underdrive the compressor which they did, ordered, installed, same exact scenario happens. ends up changing pulley ratio from 1.7 to 1.5, basically at 2200rpm it slows the compressor down about 800rpm. and puts it closer to where stock pulleys at cruising rpm would have been.

I guess next step is to get system up to temp and hold 2000+rpm in park and rear gauges and see what low side looks like? possible its just over filled but only n issue with higher rpm?

not having a real idea of how much charge the system should hold - ball parked it off a no rear a/c yukon to start with - 25.60oz of r134a/7.10oz of PAG46
i spread the 7.10 oil around as i put it all back together, compressor getting about 4oz and the rest split up. added maybe an oz to the chiller. r134a i start with a solid 2 can charge - then after about half of the third i'll add very slowly, cut it off, let run, check temp at vent and intercooler.

i guess what i need to know if how to determine correct charge
any help guys please!

thanks

[bohica2xo]

You are moving a lot of heat. The refrigeration system seems to be settled at this point. 275 psi on the high side is no issue at all for an MVAC system.

You are getting a cool cabin and IAT. I would not reduce the compressor speed if it is working well.

The angry snail makes a lot of heat. Assuming a water cooled cartridge, some of that goes in to the coolant. Your ECT climbs when you load the engine pushing that barn door down the road at 75mph. This would suggest you may need more radiator area.

Pay attention to the water pump speed. Do not reduce it below OEM speeds. Since you are not swinging a fan, you can increase it a little too. One of the jobs of the water pump is increasing the coolant pressure in the block. This prevents nucleation of the coolant at the surface of the hot metal.

What is the ambient temperature for you right now? And what sort of ECT's are you seeing?

You can always road test the system with the gauges duct taped to the passenger side of the windshield - use a helper or a gopro and jump on the highway