A/C low side pressure
Thread Starter
4th Gear
Joined: May 2017
Posts: 4
Likes: 0
A/C low side pressure
Hi guys, I'm new, and first post. I did work as an automotive diriveability tech for many years, so hopefully my questions and comments won't sound too goofy. I have a 2001 Z06, and it recently leaked out the freon. This took a number of years, with very little driving/use, so I'm assuming it ranks among the world's slowest leaks. Anyway, it worked GREAT when it was working, so I am pretty sure everything is in order. I tried using the easy R134 loading, with only the low side guage the other day. My label says it takes 28 oz. After only about 6, it started working again. I had depressed the low side needle valve before hand, just to see if it hissed, and it did. So I don't know how much was left in the system, when I started the process. It was 100* ambient temperature, and according to my guage, I couldn't get past 40 lbs, even after about 18 oz, which is all I had. It now works wonderfully, but I just wanted to verify from the guys who should know, if these A/C systems are like the others, as far as low side pressure goes. Should I leave it alone, or add more until it comes up to the 45-50 lbs, you would normally see?
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
Refrigerant expands with heat and builds more pressure when the ambient temperature is hotter so the pressure varies. I put a meat thermometer in the vent with the windows down, ac on max and engine at operating temperature. The thermometer should read around 42-45 deg F.
Thread Starter
4th Gear
Joined: May 2017
Posts: 4
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Hey, thanks for the reply. The question here isn't really how well it works. It works exceptional, compared to other automotive A/C systems I've felt. One factor on the low side pressure, has to do with the slow leak. The more I add, the longer it should work, in theory. I just want to know if I can safely add, until I reach 45-50 lbs. If this system is like most others, I should be able to do that.
Safety Car
Joined: Mar 2016
Posts: 3,534
Likes: 432
From: Atlantic Beach FL.
A little extra shouldn't hurt if the compressor is in good health. When the temps go up then there is too much.
I have see people over fill the crap out of them thinking more is better. When the temps go up they can't figure out why lol.
I have see people over fill the crap out of them thinking more is better. When the temps go up they can't figure out why lol.
Instructor
Joined: May 2006
Posts: 202
Likes: 16
The best way (only real way) to check the amount of 134a in the system is to remove & measure it in an A/C charging station.The machine will allow you to put the correct amount of refrigerant in the system. Another advantage of using a machine is that you will also dry out the system using a high vacuum. That said, it is unlikely that you could have overcharged it using the low side & compressor vacuum.
Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
...I tried using the easy R134 loading, with only the low side guage the other day... ...It was 100* ambient temperature, and according to my guage, I couldn't get past 40 lbs, even after about 18 oz, which is all I had. It now works wonderfully, but I just wanted to verify from the guys who should know, if these A/C systems are like the others, as far as low side pressure goes. Should I leave it alone, or add more until it comes up to the 45-50 lbs, you would normally see?
Refrigerant pressures depend not only on the ambient temperature, but also on humidity and the RPMs of the engine.
Take a look at this post. It has detailed instructions to check/add refrigerant and a pressures chart that take into consideration all relevant parameters.
