Automotive Air Conditioning Information Forum

I have my wife's 2016 Chevy Tahoe that a/c had an evaporator leak. I replaced the evaporator and the expansion valve and seals. Checked the rear evaporator no leaks detected. I did vacuum the system and held a negative 30 vacuum for 30 minutes. The a/c was really cold and then just seemed to die or only cold on driving conditions. The back seems to be colder and lasts like 2 weeks at cold not very cold but ok. I did have to add detector to system and yes did try sealer also. When it wasn't cooling I placed the gauges on the system and low side is holding at 30-35 and highside at 150-200 at 90 degrees. With engine turned off system equalizes to with psi between low and high side. Please help if you can thinking maybe I have to much liquid build up data plate says .92kg PAG Oil this is alot? please help with suggestions or comments? Thank you,

Ouch! I don't know about liquid buildup, but you def, have too much sealer build-up.
Although they seal that sealer stuff in the stores, it is the worst thing by far you can put into your system. It should be taken off the market.
Please, NEVER use sealer. The only substances that should be in any AC system, whether car or house, is the refrigerant and the accompanying oil.

Let's see if the others can offer any hope......

The .92 kilogram specification (34.4 ounces) is a measure of weight, not "fluid ounces" as the oil would be measured. So .92 kg. has to be the weight of the refrigerant, which makes sense. I'm guessing because I don't have the specs for your vehicle, but I'd say that with rear A/C, this system takes around 10 fluid ounces of PAG-46. So if you actually DO have .92 kg. of oil in the system--possibly more than three times the amount that should be in there, depending on how you measure--the first order of business is to get all of that oil out.

Sealer is a whole 'nuther issue. It could very well have clogged up one or more components, compounding the problem of lack of cooling.

Oh didn't mean to imply I added .92 kg, I was trying to put as much info I could. I did notice also front vent tube blowing warm air out and rear is colder and condensate is dripping front is not. A now expansion valve lines are just cool at front and warm going to rear. Pressure is in range for vehicle specs. Idk everything shows it should be ok but it's not. Thinking of maybe flushing system. Unless someone can give me other options or things to try

Sealer likes to clog expansion devices, evaps, and condensers

Does this vehicle happen to "live" in the Rust Belt? I ask because the OEM aluminum lines to the rear evaporator have a habit of corroding and leaking when exposed to ice melting chemicals during the winter months. If inspection and testing indicate the need for new front-to-back lines, barrier hoses to replace the original metal lines are available through the site sponsor.

Regardless of whether the front-to-back lines need replacing, also check the gap between the compressor clutch plates. It should be about 0.020" +/- 0.005". If it's okay, I would consider thoroughly flushing the system to clean-out all the old oil, and hopefully, most of the sealer. Flushing the system would include the evaporators and all lines without mufflers. Lines with mufflers will have to be replaced. Flush the compressor a few times as well using only the appropriate PAG oil--no solvents. Then replace the expansion devices, accumulator, seals and o-rings, and the condenser. Generally speaking, the newer parallel-flow condensers with micro-passages can't be effectively flushed.

After completing all of the above, distribute the correct amount of PAG oil to the compressor and various components; reassemble everything using Nylog Blue (sparingly) on all o-rings, seals, and flare fittings; evacuate for a couple of hours; and recharge to specs.

I'm not even convinced you have an AC problem. You removed the front HVAC, opened it, replaced the evap, put it back in.

Do the heater blend doors function properly? Can you go full hot on the controls with fully warmed up engine and blast hit air out? Can you go full cold and blow a little warmer than ambient air without the AC on? Do all the modes work properly? Did you use a GM replacement evap? Or an aftermarket that didn't fit very well?

JoJo36134 wrote: ↑Sat Apr 30, 2022 4:19 pm A now expansion valve lines are just cool at front and warm going to rear.

With the system engaged and the engine running at about 1,800 RPM, can you clarify which lines are warm and which ones are cool? In a properly operating system, the larger diameter lines should be cold and the smaller diameter lines should be hot. Did you measure the temperatures using a thermometer or just go by touch?