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General Recharge Question

jed1154 on Thu June 26, 2014 11:13 AM User is offline

I was reading and watching videos about recharging a system and checking pressures. I was also doing some reading about how to add oil to a system if you replace components, like a compressor, and it looks like its added directly to the compressor.

But what if you have your system evacuated? Does all of the oil remain in the sytem and only the refrigerant separates and comes out?

GM Tech on Thu June 26, 2014 12:17 PM User is offline

A/C terms 101:

evacuated- means a vacuum pulled, no air in system- ready to add refrigerant- oil cannot be pulled out with vacuum

recovered: means all refrigerant has been sucked out of system by a recovery machine- and a good one has an oil separater that will measure the oil removed with recovery- if any

and yes, the oil typically stays in the system- unless your recovery ports on low and on liquid line- which is rare to be low- (factory uses this to fill system)

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

jed1154 on Thu June 26, 2014 2:10 PM User is offline

OK, so, if you had a leak for instance, say a fitting or a line...and the system was empty, you evacuated (as per the terminology), then you would not need to add oil back in?

Second question: I understand that it is best to evacuate a system and refill it. However, what about a system that has no leak, but has the potential to be underfilled or overfilled (due to previous work)? Would it be suitable to simply add or remove based on 'pressures'?

Dougflas on Thu June 26, 2014 2:38 PM User is offline

Quote
Originally posted by: jed1154
OK, so, if you had a leak for instance, say a fitting or a line...and the system was empty, you evacuated (as per the terminology), then you would not need to add oil back in?



Second question: I understand that it is best to evacuate a system and refill it. However, what about a system that has no leak, but has the potential to be underfilled or overfilled (due to previous work)? Would it be suitable to simply add or remove based on 'pressures'?

no, the best thing todo is recover the charge and weigh the correct amount back into the syatem.

jed1154 on Mon June 30, 2014 12:50 PM User is offline

What is the procedure for removing pressure from your gauge set after checking the vehicle out? I have manual QD connectors, so once I sever the gauges from the vehicle, the lines themselves still have pressure. The last time I did it, I just unscrewed the yellow hose a little and eased out the pressure. Lots of oil and dye though this way.

GM Tech on Mon June 30, 2014 12:56 PM User is offline

I make sure low side port valve at car is open, then I close high side valve at port on car, then open both crank valves at guages ,with car running and a/c on that then allows the system to suck in the refrigerant from both high and low sides of my gage set- which was also considered as part on the "weighed-in" charge.

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

jed1154 on Mon June 30, 2014 2:53 PM User is offline

OK, so my yellow hose will not suck 'air' if its not on a can? The end of that is sealed?

Cussboy on Tue July 01, 2014 2:28 PM User is offline

Quote
Originally posted by: jed1154
OK, so my yellow hose will not suck 'air' if its not on a can? The end of that is sealed?

The yellow hose will not suck in air if the two service manifold gauges are closed. Once the yellow hose is attached to a source of refrigerant, bleed that air out of the hose by loosening the connection of the yellow hose at the manifold end SLIGHTLY for a FEW SECONDS.

Of course, always wear eye protection when around refrigerants (or the battery).

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