OT Another Air Conditioner Problem

I recently bought a 2013 Silverado 1500. At only 40,000 miles, there is a strange air conditioner problem.

There is a leak "somewhere" that I can't find. It appears someone has been fighting this before me, it has dye in it, probably why they sold it...

But even when I add refrigerant, the pressures don't come in right. To get the high side up to where it needs to be, the low side is way high. This evening, at about 98-100*, engine revved up to 1500RPM, I added 12 oz. to get the high side up to around 300, the low side went up to 65! The cooling is minimal.

When I first bought it, I drove it on a cool day, around 85*. It worked well. But later discovered if it was warmer, mid 90s or above, it was slow to cool and only got slightly cool. A couple days ago, it rained on the way home, the air was basically just air, little cooling. I thought it must have lost the charge, but the next day, it was blowing cool again.

I suspect the leak is in the evaporator since I can't find any thing with the UV light. I also suspect it may have air in the system.

But then I found this article. Not sure if mine is equipped with this or not, but sure sounds like my symptoms.

Any ideas?
Thanks!
refrigerant control valve

If it has dye in it an evap leak will show up at the drain with the light.

You probably are overcharged,and that article/tech tip could be correct.You overcharged it trying to compensate for the lack of cooling most likely.If you replace this valve,you would need to evacuate the system,and weigh in the correct charge.Mark

Sounds overcharged to me. I have issues with replacing individual components on compressors. Example; The compressor clutch died on my old Geo. Shopped all around for a clutch and the cheapest I could find was something like $100. A complete rebuilt compressor with clutch cost only $35. Needless to say I bought the compressor and swapped the clutch to avoid discharging the system. Under these circumstances (valve) forget the components and replace the whole thing.

What are the pressures at idle? Also a static reading of the pressures with the engine off?

You are way overcharged. Evacuate and add the proper amount. In most cases I pay no attention to the high side when charging ac systems. As long as the low side hangs around 30-40 psi it will cool. 300 sounds way too high anyway. Bearing in mind that the ambient temp is 100 I still would only like to see around 200 on the high side.

EXACTLY. The condensing pressure of R-134a at 100? F is only 125 psi. Don't know why the OP "wants" to see 300 psi on the high side.

I'm going by this chart.

Is this incorrect?
134 pressure chart

Hello Steve@Advance,

The article you linked to is garbage. Pressure readings with out ambient temp are useless! Your pressure chart seems correct. Look at your low side pressue chart, and look and your low pressure reading. A bit overcharged for the ambient temp? Or heat intrusion. Weak suction side of the compressor is also a possibility. If was overcharged, first thing that suffers is the compressor. The Reason I say that, high side is also low for the ambient temp. Vice grips and a couple of washers to the coolant line feeding the heater will prove heat intrution. Another clue would be tons of condensate, and higher then normal vent temp. High side pressure is all about proper air flow. Keep me posted, I have more........................... Have fun fin ding the leak,

GUIDO.

I'll add a couple of things to look into. First, your pressures are WAY OFF. You do not need to go up to over 300 on the high side under ANY circumstances. Low side should run around 25 to 50. Compressor should cycle off at around 22 to 24, high side should run around 300 to 250 depending on ambient temperature. On a cooler day, it may run as low as 175.
I suspect due to the poor cooling, you have either air in the system or too much oil in the system. I suggest that you have the system recovered and evacuated. This will pull most of the oil out of it.
With dye in the system, you should also look it over with a black light in an indoor environment where the ambient light is well below daylight level. A leak will show up quite obviously.
There is more to an A/C system than just having the pressures right.

Poor cooling can also be caused by a heat/cool door not operating properly.