Automotive Air Conditioning Information Forum

Hello there, I'm new to this forum and I'm here cause I need some guidance from those who are smarter or more knowledgeable than me. I rarely run into something I can't figure out on my own but this one kinda has me stumped and in this case I'm neither afraid or ashamed to ask for help!

The issue at hand is that I have a customer with a 2016 Tahoe that is blowing warm air in the front and semi cool air in the rear. About 2 years ago on the same vehicle I replaced the compressor, condenser, drier, and both front and rear TXV's. Also did a full system flush and replaced all the orings on the system at that time. I did all this because he had a bad leak at the compressor and I got all the above listed parts with the flush, oil, and refridgerant in one complete kit.

Fast forward to today. His system has been working flawlessly and blowing ice cold up until earlier this week. I hooked my gauges up and pressures were about spot on where they should have been for an 87 degree day. 45-50 on the low, pretty steady 200 on the high. Water is dripping like crazy from the condensate drain which tells me that the Evaporator must getting pretty cold however the suction line coming out of the firewall feels warm which has me a bit puzzled. Also on my scan tool, the evaporator core temperature was showing 87 degrees which matched ambient air temp and again has me puzzled....Why is it condensating and dripping so much if its 87 degrees? The blend doors appear to be functioning because I can cycle from hot to cold no problem and I can see on the scan tool that the "desired" and "actual" blend door positions match so I've ruled those out as being the culprit. What could be going on here? Pressures good, dripping like crazy from the condensate drain, blend doors functioning, but no cold air and the suction is warm. Rear blows cool but not cold.....IM STUMPED!

Get'r'done wrote: Thu Jun 19, 2025 6:00 am I hooked my gauges up and pressures were about spot on where they should have been for an 87 degree day. 45-50 on the low, pretty steady 200 on the high.

1. Were these pressure readings taken at about 1800 rpm?

2. Did you pull out the refrigerant and weigh it to confirm correct amount?

Get'r'done wrote: Thu Jun 19, 2025 6:00 am About 2 years ago on the same vehicle I replaced the compressor, condenser, drier, and both front and rear TXV's.

Doesn't this vehicle have a front orifice tube and a rear TXV ?

Cusser wrote: Thu Jun 19, 2025 6:08 am

Get'r'done wrote: Thu Jun 19, 2025 6:00 am I hooked my gauges up and pressures were about spot on where they should have been for an 87 degree day. 45-50 on the low, pretty steady 200 on the high.

1. Were these pressure readings taken at about 1800 rpm?

2. Did you pull out the refrigerant and weigh it to confirm correct amount?

Get'r'done wrote: Thu Jun 19, 2025 6:00 am About 2 years ago on the same vehicle I replaced the compressor, condenser, drier, and both front and rear TXV's.

Doesn't this vehicle have a front orifice tube and a rear TXV ?

I did not pull the refridgerant out and weigh it. I figured since it was dripping so much water and pressures reading so well that it was not a charge issue but i could be wrong i guess. Also the fact that this happened so quickly. Owner said it was blowing cold, parked it for a couple hours and drove it again and immediately noticed it wasnt cooling. Readings were at both 2000 rpm and idle. The high stayed at 200psi with very minimal fluctuation between idle and 2000 rpm. The low would drop from 50 to 45 when revved.

This has 2 expansion valves. 1 mounted to the firewall and one mounted at the rear of the vehicle that can be removed from the bottom.

Any ideas anyone? I'm absolutely stumped and I don't want to throw the parts cannon at this thing. I like to be 100% sure in my diagnosis before I take customers money. Thanks in advance ya'll!!!

Guess I've got everyone else stumped too.
Im probably going to replace the front and rear TXV's since they are under warranty and recharge the system and see what happens

First thing I'd do, as already suggested, is to recover the charge and see what it weighs. If it's low, the system probably has a leak somewhere.

The high pressure seems a bit low to me, further suggesting a low charge.

I'd look up the specs for you, but I'm traveling outside the USA right now and don't have access to my files.

The issue has been resolved. I recovered the refridgerant and it was just a hair low and I mean a hair. Not enough I think to make the system not cool at all. I replaced the front and rear TXV's and recharged the system and it's up and going again blowing ICE cold. Pressures after recharge are almost identical to what I had before. The only thing that changed was the high side was showing 225 now instead of 200 but it was also almost 10 degrees hotter outside too which I would expect this.

I'm still confused as to the readings I was getting before and why the TXV's fixed it. If it was a TXV sticking closed wouldn't I get a really high reading on the high side and a really low reading on the low? Also if it was sticking open wouldn't I have a high low side reading and low high side reading? This is going to be a mystery that haunts me for some time!

Either way, my customer is taken care of and happy. I did this job as a courtesy free of charge since he spent so much money with me to have dang near his whole system replaced 2 years ago.

THANKS TO THOSE THAT CHIMED IN!