AC Trial and Error

[isomswim]

Alright posting some of my trial and error with the AC system.

1999 GMC Suburban 1500 5.7 with rear AC
- Everything replaced, I mean everything
- Sanden style UAC Compressor
- Evaporators front and rear
- Parallel Flow Condenser
- Hoses front to Rear (Auto Cooling Solutions for the Rear)
- Orifice tube Currently installed - Red 0.062
- R152 - Approx. 24 ounces maybe a little more
- HD Clutch
- 11 Blade fan

This is how it currently sits, and by far the coldest, I've been able to get it. It's now comfortable to drive in the TX heat, at least 85-90 right now in the morning. If I try to put more R152 in the low pressure shoots up well over 75-80, I assume this is from the chosen Orifice tube, as High stays roughly steady around 200 or less.

Items to Install
- OEM Condenser Electric fan
- "blanket" for the Accumulator
- Accumulator Pressure switch

I've considered the Smaller pulley Compressor but it makes me wonder if it will do anything as flowing more Refrigerant is going to be limited by the Pressure Devices, Orifice tube and TXV. I know there is a lot of Knowledge here, my background is in Mercedes Benz vehicles, but of course I work on my own stuff.

 

[Coveman]

I have a 99 burb too, still on 134a and gets like a meat locker inside. I haven’t used 152 in a vehicle, but for our trucks a full load of 134a is 3 pounds 8 ounces, should the volume of 152 be that much lower?

Did the system hold a vacuum ok?

 

[isomswim]

I have a 99 burb too, still on 134a and gets like a meat locker inside. I haven’t used 152 in a vehicle, but for our trucks a full load of 134a is 3 pounds 8 ounces, should the volume of 152 be that much lower?

Did the system hold a vacuum ok?

Oh yeah everything is sealed tight. Pulled vacuum this last time about 30+minutes. On the note of 152a charge should be about 60% of 134a charge from the Google and forum research I've found

 

[1998_K1500_Sub]

@L31MaxExpress has posted on his use of R152, you might search for "R152" in posts from him.

He's used the Sanden compressors and recently discussed the use of a higher-displacement compressor, a Four Seasons 10-cyl 210cc/rev HT6. See this thread (if you haven't already):

New Sanden Compressor: High Suction/Low Discharge Pressure?

Followed procedure in FSM which closely matched the Sanden instructions, so I *think* the oil charge is right. The old compressor didn’t detonate. It just leaked. No sign of debris in hoses or accumulator (replaced accumulator with new). 97 burb with front and rear air. Had both on full, the...

www.gmt400.com

This thread covers a lot of ground regarding AC performance (not just compressor pulley size like its title suggests):

Better AC with different size pulley?

With the recent heat wave, the AC once again leaves a lot to desired once idling in the torturous midday sun. Had my AC guy check the refrigerant, pressures, airflow, etc. All was good. The AC is great if it’s below 90 outside. Once it gets over 90 it starts struggling at idle. I can elevate...

www.gmt400.com

 

[L31MaxExpress]

Alright posting some of my trial and error with the AC system.

1999 GMC Suburban 1500 5.7 with rear AC
- Everything replaced, I mean everything
- Sanden style UAC Compressor
- Evaporators front and rear
- Parallel Flow Condenser
- Hoses front to Rear (Auto Cooling Solutions for the Rear)
- Orifice tube Currently installed - Red 0.062
- R152 - Approx. 24 ounces maybe a little more
- HD Clutch
- 11 Blade fan

This is how it currently sits, and by far the coldest, I've been able to get it. It's now comfortable to drive in the TX heat, at least 85-90 right now in the morning. If I try to put more R152 in the low pressure shoots up well over 75-80, I assume this is from the chosen Orifice tube, as High stays roughly steady around 200 or less.

Items to Install
- OEM Condenser Electric fan
- "blanket" for the Accumulator
- Accumulator Pressure switch

I've considered the Smaller pulley Compressor but it makes me wonder if it will do anything as flowing more Refrigerant is going to be limited by the Pressure Devices, Orifice tube and TXV. I know there is a lot of Knowledge here, my background is in Mercedes Benz vehicles, but of course I work on my own stuff.

Mine was running that kind of low-side pressure at idle last summer with the wrong/malfunctioning rear expansion valve in it and the Sanden.

Smaller orifice tube reduces the low-side pressure. I ended up changing the rear expansion valve twice before I managed to get one that operated correctly. The first China made unit was listed wrong interchange wise and had 2x the BTU rating that was needed. The 2nd was a Made In USA Old Air Products valve for their Hurricane unit. My 97 has an aftermarket rear system that uses SAE threads though where the later factory R134a systems use Metric threads.

Is the parallel flow condenser you installed 34" wide at the core. Alot of places as selling a ~26" wide single evaporator truck condenser rather than the correct wider dual air SUV unit.

This is when my 97 would not cool well at idle. Rear expansion valve flowing too much and the weak Sanden.

You must be registered for see images attach

This was after swapping the rear expansion valve and with the 10 cylinder HT6.

You must be registered for see images attach

 

[L31MaxExpress]

The dual air SUVs should not have an orifice tube at the condenser outlet either. It goes inline over the inner fender after the rear line Ts off the liquid line off the condenser. The front orifice location is very close to the air filter housing on the Vortec SUVs.

 

[L31MaxExpress]

I will also add that the Sanden 4261 with the smaller 4.x" pulley struggles at idle even on my single evaporator G20 van I installed it on. I know the 10 cylinder would work noticeably better on it around town as well. I am getting 40F at 1,500 and 35F at 2,000 rpm with the van stationary and the pusher electric fan running in 103F ambient and 35% relative humidity, but idle warms up to 45-50F.

 

[isomswim]

Interesting about the rear Expansion valve issue you had. Mine is an OEM part direct from GM parts store. Iade the mistake of doubling the O-Tubes and that sucked, even tried a white one with full R134 before finally using Red and 152. Maybe I'll swap for the 10 cylinder just not sure I want to make the $200+ investment after all the errors, but what's a guy to do

 

[L31MaxExpress]

Interesting about the rear Expansion valve issue you had. Mine is an OEM part direct from GM parts store. Iade the mistake of doubling the O-Tubes and that sucked, even tried a white one with full R134 before finally using Red and 152. Maybe I'll swap for the 10 cylinder just not sure I want to make the $200+ investment after all the errors, but what's a guy to do

I had a genuine Sanden 4261 and was on the same fence before swapping the 88947 on my 97 Express. I had previously read a lot of positive reviews on the Sandens then realized none of them were in Texas heat. Went to my local Oreilly, picked one up with an extra orifice tube and accumulator so it has an alleged lifetime warranty. I had just been through the whole system prior. Swapped the compressor, vacuumed it out, re-charged it. As soon as I saw the low side pressure holding 40 psi with both blowers on high speed, I knew it was going to cool well.

 

[yevgenievich]

For serpentine condensers I found OSC 4544 to be closest in thickness to original. It is slightly larger than 4721.