AC stopped taking R134a

[rcdatadude]

I have 98 k1500 that lost all of it’s refrigerant. I haven’t driven it in a while and high side developed a leak. I replaced the AP connector and drew a vacuum on the system To charge it, and make sure it didn’t have any leaks. The truck shows to take 2lbs of r134a. I had 3 12 ounce cans. It took the first two cans just fine. The compressor started cycling. I got to the third can and I couldn’t get any more in the system. I was looking to add another 8 ounces. Any ideas why it would stop taking freon after two cans went in successfully? The compressor has been changed a couple of times by a dealer over the years. Could it be that replacement compressors take less Freon and it stopped when it got full. That doesn’t seem right, but I normally don’t work on the AC. Thoughts?

 

[Erik the Awful]

Does it blow cold and are the pressures correct? Did you warm the can as you added refrigerant?

 

[1998_K1500_Sub]

I got to the third can and I couldn’t get any more in the system. I was looking to add another 8 ounces. Any ideas why it would stop taking freon after two cans went in successfully?

Put the last can in a pail of hot water. That will raise the can's pressure notably above the low-side's typical operating pressure.

When you tapped the third can, I'm guessing you pulled some vapor and, so doing, lowered the temperature of the contents. Then, the now-cooled can developed little pressure relative to your low-side pressure, which with the existing charge you had put in was probably in the range of 35-40psi... and vapor stopped flowing or flowed slowly.

 

[rcdatadude]

To be honest, I was adding based on weight and what I read about the specs on the system. It was blowing cold air, but I didn’t have a thermometer to read the temp. I want to say The pressures were 25-30 on the low side and 100 on the high side depending on whether the compressor was engaged.

 

[Nad_Yvalhosert]

2 lbs, 16 oz the pound, 32 oz
3 cans, 12 oz each, 36 oz
Took 24 oz but no more

Is that right?
Engine running? A/C on max, fan on low?
What was the ambient temp the day you charged it? If it was too low the cycling pressure wouldn't draw down enough to suck in any more SUVA

 

[Erik the Awful]

25-30 on the low side and 100 on the high side

If that's the case, that's too low and you're undercharged. Warm that can. I like finding a place in the engine bay that is very warm, but not too hot to rest my hand.

 

[rcdatadude]

2 lbs, 16 oz the pound, 32 oz
3 cans, 12 oz each, 36 oz
Took 24 oz but no more

Is that right?
Engine running? A/C on max, fan on low?
What was the ambient temp the day you charged it? If it was too low the cycling pressure wouldn't draw down enough to suck in any more SUVA

Correct with the exception of the fan being on low. My son (he’s driving the truck now) switched it on while I getting everything else ready. I’m not completely sure. He might had it in a higher setting. Just curious what the pressures should be as the compressor cycles on and off.

 

[rcdatadude]

Does it blow cold and are the pressures correct? Did you warm the can as you added refrigerant?

That is something I did not try. I will connect the manifold guages and try to add the last 8 ounces. Thanks!

 

[Nad_Yvalhosert]

Correct with the exception of the fan being on low. My son (he’s driving the truck now) switched it on while I getting everything else ready. I’m not completely sure. He might had it in a higher setting. Just curious what the pressures should be as the compressor cycles on and off.

Hard to say. On-off pressures vary based on current ambient temp and humidity.
25 to 100 sounds low to me. On an 80° day my gauges showed 12 on the low and 120 on the high and my Yukon was... let's just say it was tough to look my wife in the eyes. My attention was, uh, elsewhere.

 

[rcdatadude]

Correct with the exception of the fan being on low. My son (he’s driving the truck now) switched it on while I getting everything else ready. I’m not completely sure. He might had it in a higher setting. Just curious what the pressures should be as the compressor cycles on and off.

Also, I was told to move the can from side to side as the refrigerant flowed. I noticed liquid moving in the viewer of the manifold guages. That’s how I determined that the refrigerant stopped flowing. I’m assuming vapor could still be moving into the system?