My 99 Tahoe's AC is cold up front but hot in the rear

[L31MaxExpress]

Automotive air conditioners will only cool to 30° below ambient temperature, and the average car AC could cool a 3 bedroom house. Don't know for sure that these things still are completely true, but these are two things that that they taught us in the AC Delco training courses back in the 70s and 80s. This was before R134a, still R12 back then, and the newer refrigerants are supposed to be more effective and efficient.
A lot of shops back then would have a big box fan, like you'd use to cool the shop, in front of the car, blowing on it. Dad did this on several of our family's cars when recharging in the summer, and he felt that it helped.

Mine cools more than 60°F below ambient in 102F weather. R12 was a much better refrigerant. I remember riding around in the 83 G20 van I still have as a kid. It would nearly give you frostbite during the summer.

 

[HotWheelsBurban]

Mine cools more than 60°F below ambient in 102F weather. R12 was a much better refrigerant. I remember riding around in the 83 G20 van I still have as a kid. It would nearly give you frostbite during the summer.

Yes I agree, a properly working AC should get plenty cold. That's the sad part about the '06 not being usable; the freaking AC would about freeze you out, and the Bose stereo worked great. Everything that makes it driveable quit working or broke.....

 

[L31MaxExpress]

Yes I agree, a properly working AC should get plenty cold. That's the sad part about the '06 not being usable; the freaking AC would about freeze you out, and the Bose stereo worked great. Everything that makes it driveable quit working or broke.....

My 97 van and 99 Tahoe will both freeze you out. The 83 would also freeze you out. My brothers 99 suburban would freeze you out too.

 

[Eveready]

As I mentioned in another post. In the South a working AC is non negotiable. Mine will work in every vehicle if I have to mortgage the house. I might sell the kids and the dog, but the AC will work!

 

[Erik the Awful]

Automotive air conditioners will only cool to 30° below ambient temperature, and the average car AC could cool a 3 bedroom house. Don't know for sure that these things still are completely true, but these are two things that that they taught us in the AC Delco training courses back in the 70s and 80s. This was before R134a, still R12 back then, and the newer refrigerants are supposed to be more effective and efficient.
A lot of shops back then would have a big box fan, like you'd use to cool the shop, in front of the car, blowing on it. Dad did this on several of our family's cars when recharging in the summer, and he felt that it helped.

When I was a tech, the manual's A/C test said to park the vehicle in the shade for half an hour with the windows down, then run the A/C with the engine at 2000 rpm for fifteen minutes and take the temperature out of the center vents. On a 100° day it should be blowing 40-45°. We had customers bringing in brand new black Maximas with un-tinted windows complaining the A/C wasn't working. We run the test and the cars would blow 37° air. The customers wanted to turn the A/C on and have the car immediatley chilled. All we could do was give them a business card for the nearest tint shop.

R-12 was significantly better than R-134a for cooling, but old school A/C techs were just venting that stuff all the time. I think the switch to R-134a was partly done just to institute new tools and procedures to get people to be more conscious about conserving the freon and reusing it.

 

[HotWheelsBurban]

When I was a tech, the manual's A/C test said to park the vehicle in the shade for half an hour with the windows down, then run the A/C with the engine at 2000 rpm for fifteen minutes and take the temperature out of the center vents. On a 100° day it should be blowing 40-45°. We had customers bringing in brand new black Maximas with un-tinted windows complaining the A/C wasn't working. We run the test and the cars would blow 37° air. The customers wanted to turn the A/C on and have the car immediatley chilled. All we could do was give them a business card for the nearest tint shop.

R-12 was significantly better than R-134a for cooling, but old school A/C techs were just venting that stuff all the time. I think the switch to R-134a was partly done just to institute new tools and procedures to get people to be more conscious about conserving the freon and reusing it.

I have heard that too, about 12 being better. Also heard that the patent Dupont had on 12 expired, so they came out with 134a so they could control the market. Now there's a R1234, I have heard the same thing about it....One of the reasons my cousin bought the particular 2015 Silverado he did, was he checked it out and it was set up for (and had)134a. He's been servicing car AC since he was 13(he's 59 now) so I believe him on AC stuff.

 

[Erik the Awful]

Yeah, I don't doubt that DuPont's trying to control the market by making the manufacturers upgrade to the latest. If only there were anti-trust laws in place to keep companies for monopolizing the market...

 

[L31MaxExpress]

I have heard that too, about 12 being better. Also heard that the patent Dupont had on 12 expired, so they came out with 134a so they could control the market. Now there's a R1234, I have heard the same thing about it....One of the reasons my cousin bought the particular 2015 Silverado he did, was he checked it out and it was set up for (and had)134a. He's been servicing car AC since he was 13(he's 59 now) so I believe him on AC stuff.

My mom's 2019 Titan has R1234YF as well. The thing has a massive condenser and a PWM electronically controlled fan clutch that stays engaged while the ac is cooling the interior in hot weather. Works very well but it has a giant flame emblem on the ac label and the manufacturers could have just used R152a instead.

 

[L31MaxExpress]

So much for the 30°F difference, that is one weak AC. I did the R152a swap in the 2011 Pathfinder today. It was 109°F in the shade with 111°F heat index and the ambients in front of the condenser were 116-118°F over the asphalt in bumper to bumper traffic on the way home. Previously with R134a it was getting down to 44°F in 102°F temps with the ambients 105-108°F.

Just showing typical pressures I mentioned before getting over 300 psi in hot weather. 1,500 rpm while charging. My thermometer was showing 112F in the grille inlet.

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Immediately after pulling into the driveway on my way home this evening. Both front and rear blowers on high fan speed. It was down to 36-38F while driving at no more than 45-50 mph, will get colder running 70-80 mph down the highway.

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After the temps stabilized, idling for 5 minutes.

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[1998_K1500_Sub]

I added three 12oz cans and stopped there because the low pressure gauge was at 75psi and the high was at 225-230psi. I didn't want to overfill or cause damage.

Your high-pressure reading doesn't suggest "overfilll" to me.

The suction pressure seems high. Is there any reason to suspect your compressor has been compromised, that it's not pumping like it should?


One other thing: Evidently there's some confusion about where the orifice tube resides on the Suburbans with rear air. See here:

Suburban rear A/C expansion valve location?

We put the orifice tube in the line by the evaporator core just like on pickups, but there wasn't one in there to begin with. So are the Suburbans not supposed to have one there and have it instead in the location of that diagram or should it be in both? (for someone's benefit in the now or in...

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