Could really use some help - AC

[L31MaxExpress]

Hmmm.... Highly compressed highly flammable gas circulating in passenger compartment. Is this about cooling efficiency or the green left pushing any product to support a green agenda.

R134a is just as flammable in a rapid release scenario. The highly atomizes PAG oil burns.

Also you might want to avoid any vehicle built in the past 6-7 years as they use R1234YF which is flammable as well.

I bought a window unit a couple of summers ago that is R32 as well.

I have never seen a catastrophic leak into the passenger compartment of a vehicle in 25 years. A pinhole in an evaporator core yes, massive sudden release, no.

Antifreeze will burn too if you get it hot enough.

 

[chevman_88]

This is something I need to think about as my new rear lines are rubber and run right next to the 6.5 turbo downpipe (already wrapped in heat tape). I should get some heat wrap to go around the hoses in this area as well.

 

[chevman_88]

Update: System charged with R152 and swapped the compressor to the bigger four seasons unit, still not seeing cold air temps, cool, but not cold. Inspected all my connections and found one that was leaking, this one has been giving me grief as it passed the vacuum check but failed the 100psi pressure test for several different o-ring sizes until I used an oversized ring that I couldn't torque the connection down, but just tighten it enough. It's once again leaking, so I emailed Auto Cooling Solutions (they are the only company providing replacement rear lines for these) and they need some pictures of both sides of the connection. So time to evacuate again (going to wait until after we pass this next batch of triple digit days as the AC somewhat works) and get those pictures.

 

[Coveman]

I had dome light issues in my 99 burb due to the tailgate glass switch. Sumpin that might be worth looking at…

 

[Dariusz Salomon]

I use that Sanden 4440 in my Tahoe with rear ac and it works perfect. Stone cold-my wife gotta wear a blanket on her laps because of a wonderful placement of the vents on passenger side.

 

[Dariusz Salomon]

Quick question-how much r134 did you put in the system?

 

[chevman_88]

Quick question-how much r134 did you put in the system?

No R134, used R152. Ended up being somewhere between 30-40oz as I went off high and low side pressures (couldn't ever get it just right due to my leak). Supposed to be about 64% of what R134 would be at 90% of the pressure. Depending on what you read my burb is between 3.5 (accumulator sticker) to 4lbs (manual) of R134.

 

[HotWheelsBurban]

I had dome light issues in my 99 burb due to the tailgate glass switch. Sumpin that might be worth looking at…

On the passenger side, you're getting the cold air straight off the evaporator core so it should be nice and cold. My crew cab will frost my kneecaps when I ride shotgun, but that nice cold air won't get to the back seat....

 

[chevman_88]

Think I got my leak fixed. Busted out the calipers to measure evap fitting and new hose fitting and then find the o-ring that fit it exactly (apparently there's enough variance from one manufacturer to another that slightly smaller or bigger and it would leak). Passed a 100PSI test for several hours followed by a vacuum test for another several hours.

Started recharging and noticed that at idle and about 35-40psi low side my rear air would cool well, however, front air stayed warm. Bump up to ~45-50psi and front air would get cooler and rear air would start getting less cold (not warm, but not as cold as it was). Rev up to 1500 and pressure would drop to ~35psi and front air would get even colder, 2000 and pressure would drop to 25psi and front air would get even colder. Rear air didn't seem to be affected and never saw any sweating of the lines near the accumulator. Ambient temp was 90-95 (working in the evening and temps started to drop) and RH ~30%. Going to get better data tomorrow after work when I have someone to help out. High pressures never seemed to climb very high (stayed under 300) that I noticed.

Currently have an orange fixed orifice, bigger four seasons compressor, micro parallel condenser, r152 and new four seasons evaporators.

 

[L31MaxExpress]

Think I got my leak fixed. Busted out the calipers to measure evap fitting and new hose fitting and then find the o-ring that fit it exactly (apparently there's enough variance from one manufacturer to another that slightly smaller or bigger and it would leak). Passed a 100PSI test for several hours followed by a vacuum test for another several hours.

Started recharging and noticed that at idle and about 35-40psi low side my rear air would cool well, however, front air stayed warm. Bump up to ~45-50psi and front air would get cooler and rear air would start getting less cold (not warm, but not as cold as it was). Rev up to 1500 and pressure would drop to ~35psi and front air would get even colder, 2000 and pressure would drop to 25psi and front air would get even colder. Rear air didn't seem to be affected and never saw any sweating of the lines near the accumulator. Ambient temp was 90-95 (working in the evening and temps started to drop) and RH ~30%. Going to get better data tomorrow after work when I have someone to help out. High pressures never seemed to climb very high (stayed under 300) that I noticed.

Currently have an orange fixed orifice, bigger four seasons compressor, micro parallel condenser, r152 and new four seasons evaporators.

If the accumulator is not cold and sweating the system is still low on charge.

Because the metering devices operate in different manners the temperatures will not be exactly the same. Fully charged system, my rear ac is slightly colder at idle than the front. At 1,500-2,000 rpm or driving down the interstate my front ac is colder. I charge by superheat and target 6-8F superheat on the accumulator outlet. To calculate superheat, look at the R152a pressure/temperature chart vs the low side pressure and accumulator outlet temperature. I will also say you have to convert from PSIG to PSIA by adding 14.7 to your gauge reading to get the PSIA of the chart. 25 psig, 39.7 psia, corresponds to an evaporating temperature of about 34F. Thus the accumulator outlet on a fully charged system should be 40-42F. Anything less is undercharged. I charge at 1,250-1,500 rpm (the highest I can command the idle to) with recirculate on and both blowers on high fan speed. When you are charging and the suction line off the accumulator starts to get cool, slow down the charging volume and watch for a slight dip in the pressures on both sides of the systems. When cool refrigerant gas starts arriving back to the compressor the cooling of the compressor will cause the high side pressure and thus low side pressure to dip. Stop charging right at that point. Bring the engine up to 2,000 rpm. After ~5 minutes measure the accumulator outlet temperature record it and record the low-side pressure. Sitting stationary, in full sun load wi⁴th an interior that has not had ~20 minutes to cool down or more, I bet the low side pressure is more like 30 psig at that point. If it reads say 30 psig that is an evaporating temperature of 40F . The accumulator outlet should be between 46F and 48F if the system has enough charge in it. It is entirely possible the pressure is lower IF the interior is well cooled at that point. When the heat load reduces from the interior cooling off the system pressures will drop. My compressor cutout pressure is dialed in to about 18 psi which results in the refrigerant reaching a boiling point of about 24F.

As I mentioned earlier this chart is in PSIA. At sea or near sea level add 14.7 psi to the reading of the manifold gauge to convert to PSIA of the chart.

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