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Ok, this is how to pull a proper vacuum and re-charge your air conditioning system with refrigerant.

This is crucial that you do a good job here; this is where you show your worth. And this step decides how long your compressor will last, so please pull a good vacuum.

Grab a set of digital gauges or at least a set of analog gauges and a micron gauge and a vacuum pump full of fresh oil.

Hook up the Digital gauges and the vacuum pump to the air conditioner.

The middle and usually yellow hose goes to the vacuum pump, the left and usually blue hose goes to the thicker suction line and the right, normally red hose goes to the thinner liquid line.

Now open the gauges open the hoses and open the vacuum pump.

Turn on the vacuum pump and double check every access or hose to be sure there all open and your pulling a vacuum. Also double check that all your connections are tight.

 

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Let the vacuum run until you see 500 microns then close off the vacuum pump hose sealing off the air conditioning system.

(Note: Do not pull a vacuum below 300 microns or you will start to boil off your oil.)

When you see 500 microns and shut down the pump, do not disturb the gauges or touch the hoses for 10 minutes.

If the microns rise up above 1000 then you have a leak, check all your welds or refrigerant hose connections. If leak is not found with this method then a more technical approach is needed so go do a leak search and repair now.

Let’s go find your refrigerant leak now

Once leak is located and stopped, move to the top of the page and re-start your vacuum.

But, if the microns rise up a little at first but then stops and level off and stay below 1000, you’re ok and can continue to charge the system below.

Charging an air conditioning unit is a beautiful thing if done right will make the difference between a compressor that lasts 3-5 years and a compressor that lasts 15-20 years.

Close your gauges and all your hoses now. Then remove the middle hose usually it’s the yellow one from the vacuum pump and put it onto the refrigerant tank now

Now open your tank, open your red high side gauge and start filing the system. The refrigerant will flow in fast at first but, just keep jamming it in until it slows down and starts taking refrigerant slowly.

When the system starts taking the refrigerant more slowly, close down your gauges.

Now plug in the power and turn on the air conditioner, then let it run for at least 30 seconds and you’ll probably see that it’s still a little low on charge. According to your pressures, but I want you to switch you digital gauges over to display superheat and sub cooling.

You’re looking for between 5 to 20 degrees of superheat and between 5 and 20 degrees of sub cooling

In a perfect world we would aim for 10 degrees of superheat and 10 degrees of sub-cooling. But common installed units are not normally perfect so we have to charge to get both the superheat and the sub-cooling as close to the ideal 10 and 10 degrees as possible.

If you need to lower the superheat to get closer to 10, add refrigerant but do not add so much that the sub-cooling gets over 20 degrees. If you need to lower superheat, remove refrigerant. As long as there is at least 5 degrees of superheat out compressor will be ok. Determining superheat is easy with digital gauges as they do all the thinking for you and just display the superheat.

  • Adding refrigerant will lower superheat and raise the subcooling
  • Removing refrigerant will raise superheat and lower subcooling

So throttle the gauges open charging the air conditioner slowly through the suction side only. Keep charging for 10 seconds then off for 30 seconds until you drop down as close to 10 and 10 as you can get.

(Note: A low charge would be indicated by 20+ degrees of superheat. An over charged system is indicated by 5 or less degrees superheat.)

If you’re looking at 5 – 20 degrees superheat you have cold air blowing inside.

You could be done but before we give a system the all clear we always need to go inside and take the temperature split to be sure.

I think i‘m done / Let’s go take a temperature split now

If you cannot obtain that superheat and sub-cooling you need to go back and re start the matrix because you may have another problem.

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