AC issue on my ISX

[Rawze]

(08-27-2019 )SquareOne Wrote:  .... Somone who knows how to read the gauges properly can usually hit the nail on the head in just a few minutes.

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I am no A/C person at all, this is second hand info that was said to me from old-school A/C person who does cars and household units. He said there are some general rules for R134, they are ...

when monitoring the low side, the low side pressure is usually about/roughly equal to the evap core temp in Fahrenheit.

* If it is reading less than 33 psi, then there is too little in the system and its going to freeze up all the time.

* If it is more than 40+, then it is not going to get very cold inside the cab of the truck.

- Ideally a person wants to see it at about 33 - 36 range for coldest performance without worrying about it freezing up. Removing refrigerant will make the pressure drop, adding some will make it go up. <- This is only accurate when there is nothing else wrong with the system though...

-- High side is Dependant on heat exchanger efficiency/ health/cleanliness of the condenser on front of truck. roughly 350psi is the highest you should see on most trucks, fan should kick on to reduce it below this. The more efficient you can get the condenser (ensuring it is clean, fan works properly, etc), the more heat it will pull away and the colder and more efficient the cold side becomes.

A person should always ensure the system is working properly and the condenser and evap are very clean. Start there first. Next is to empty the system, pull a hard vacuum on it and leave the vacuum pump running for an additional 20+ minutes to burn off all the moisture as well. Moisture will not burn off until you have a really high vacuum on it, and that moisture, even a little, causes a lot of problems if not completely removed. After that, put in an exact amount (by volume or weight), recommended by the manufacturer. This should get it close enough to work most of the time. After that, it can be adjusted as stated before by a little bit up or down, but this adjustment should never be more than about 15-20% of the volume that is supposed to be in there. If it has to be adjusted more than this, something is wrong with the system somewhere.