Recharging Air Conditioner A/C

[RedBeard.45]

MY QUESTION: Why is the low pressure side (Blue Gauge) reading in RETARD? I know that is the gauge max to not damage the gauge, but why is it so high after evacuating and refilling? How much would too much refrigerant be to cause extremely low side high pressure? Maybe 2 to 3 oz? I would appreciate any help.

1st Attempt

• A/C was working, but only getting down to about 59-60°
• Checked Pressure with a DIY recharge Kit (AC PRO)
• I set the arrow on the ambient temp (80°)
• It was in the Green, but not in the Red “V” section.
• So, I began to add a 12oz can of R134a and as I was adding, the gauge went up just slightly, almost so it didn’t appear to move.
• I noticed no change in a/c temp in vehicle

2nd Attempt

• Purchased a Harbor Freight Vacuum pump and Gauge Set
• Hooked up the gauge to read and the low side was in “Retard” meaning pressure was too high. (I’m thinking because of the 12oz can I added in my first attempt)
• I began to evacuate the system which pulled both gauges down to 0.
• This took about 10 minutes to evacuate
• I left the air compressor sucking for 20 to 25 minutes after it reached 0.
• It never went below 0

Recharging the System

• My Vehicle is supposed to use 1.9lbs of r134a
• I did not have an attachment for the refrigerant can to gook to the yellow intake on the Gauges, so I disconnected it to use the a/c pro gauge
• I began to add the first can with the vehicle NOT running and it took about 8oz.
• I then started the vehicle and resumed filling with refrigerant. I continued until I felt I had put in the necessary 30.4 ounces…. Which should have been just over 2.5 cans.
• The gauge went up to the original reading that I had in step 1, and didn’t go over that spot (which was in the lower side of the green)
• The air is cooling down to 49° with the rpm’s up to 1k to 1.5k, goes down to 54-57 at 500 rmp (IDLE)

Additional Details
2006 GMC Envoy SLE 4.2l - 200k+ miles
Interior Fan blows hard
Vehicle was running with a/c on and doors open when gauges were read

 

[xavierny25]

1. It would go into retard if the compressor isn't running.
2. Compressor pump seals are shot.
Check evap coil for debris. Clean if needed.
Check condenser coil clean if needed.
Recover old freion.
Vacuum system to -30 both high and low sides. 45minutes-1hr should be more then enough.
Charge system to 1/4 of the needed amount.
Turn car on and run the a.c..
Close all doors.
Run fans at high speed DON'T FORGET THE REAR FAN.
Add Freon till compressor kicks on and continue to add freon slowly till it's at level and should be right.
There can also be other internal issues with the system.

 

[Mooseman]

Maybe the orifice tube is blocked. What about the receiver/dryer? Did you replace it? Might not be a bad idea to evacuate, replace the receiver/dryer and orifice tube. Get a can tap you can hook up to the gauges, vacuum and refill by weight.

Are you putting the right amount? Is yours an XL (7 passenger)? If not, use the smaller amount on the under hood label.

 

[fetchthecomfychair]

R134a is incredibly sensitive to over/undercharge. Meaning, the "half a can" part of your 2.5 cans charge amount is nowhere near accurate enough to get it working right. Spec is 1.9lbs, it won't cool at 1.8lbs OR at 2.0lbs, and you can't estimate +/-1oz by hand. Also, diagnosing things is about impossible unless you have real gauges with real numbers on them and can see both high and low sides at the same time under different conditions. In short, (this is an answer that I personally hate), R134a systems really need a professional with professional equipment for the recharge portion of HVAC repairs (replace the parts yourself, have a pro do the recharge).

 

[Mektek]

I have both the vacuum pump and the freon can connected at the same time. When I finish evacuating and have a vacuum that stays I close the valve on the pump and open the freon valve. That gets the first can in. For the last can, I weigh the can/tap assembly when full and leave it on the scale as I'm filling. When the weight drops to the calculated value I shut off the freon valve.
You should also have the freon can in a bowl of hot water - that helps to empty it.

 

[16vcabman]

Playing with refrigerant, you really need to know what you are doing. Freon is a trade name for R12, I think you guys are talking about r134A and it is called refrigerant. Absolutely not getting down just trying to help educate!

 

[xavierny25]

Playing with refrigerant, you really need to know what you are doing. Freon is a trade name for R12, I think you guys are talking about r134A and it is called refrigerant. Absolutely not getting down just trying to help educate!

Excuse my ignorance since I've been out of school over 22yrs. Freon aka r12 was spoken about so much when I was in school that I offend refer to all refridgerants as Freon.

 

[djthumper]

Playing with refrigerant, you really need to know what you are doing. Freon is a trade name for R12, I think you guys are talking about r134A and it is called refrigerant. Absolutely not getting down just trying to help educate!

Freon is a brand name like Kleenex, and is trademarked by The Chemours Company. Technically it is all refrigerant.

 

[16vcabman]

Yep used to be Dupont but they wanted out after the damage done. Did you put oil in the system? Usually when I recharge a system I add two onces of oil to make sure all the seals get lubed. This has worked for me for many years

 

[fetchthecomfychair]

Yep used to be Dupont but they wanted out after the damage done. Did you put oil in the system? Usually when I recharge a system I add two onces of PAG

This is terrible advice. If you don't instinctively know why it is such a bad idea, you shouldn't be working on HVAC systems.

 

[16vcabman]

This is terrible advice. If you don't instinctively know why it is such a bad idea, you shouldn't be working on HVAC systems.

I edited the oil and it didn't save the edit. As for not working on AC systems I have been doing it for 40 years and I am EPA and ASE certified. So the name of the oil name was a mistake. But if you know, why didn't you correct it instead of being nasty.

 

[fetchthecomfychair]

Adding oil without a valid reason is what's a terrible idea. That's the part you should know, and don't. Countering bad info isn't being nasty it's being correct. Nothing personal about it.

 

[16vcabman]

Well, your way may differ. If I evacuate the system I can measure what to add that's fine but if I don't know what was lost then I do two ounces. It has always worked for me. Your welcome to your opinion. I have an EPA card for 608 and 609 and I am Ase certified in 11 automotive areas but it is my opinion.

 

[Mooseman]

Now now boys, play nice. There are reasons for and against adding oil so lets leave it at that.

 

[16vcabman]

I respect your reply mooseman.

 

[fetchthecomfychair]

...and this is why the 'net is so full of wrong answers such that anybody can find an answer they like for any question, right or wrong. We must be respectful of incorrect information.

IF you know how much oil has been removed, then of course replace that amount. If your machine says none was removed then it's a safe bet none was - so don't add any! Even following the service manual's guidelines for how much oil to add for each component replaced is iffy and can easily end up with those 'problem cars' that don't work right and end up bouncing from shop to shop to shop, never getting truly fixed. I have been burned by those 'problem cars' where somebody (or a succession of somebodys) all thought it would be a good idea to add a little bit of oil just 'cause, and after a couple years of a little bit here and a dash there, the condenser ends up 3/4 filled with the crap. What then?

Don't add oil unless you have removed oil. Not an opinion.

 

[16vcabman]

Okay but at the top of this thread, the person evacuated the system and based on that there should be oil replenishment for that evacuation. That is all. Please read the above thread. And I didn't get my info from the internet.

 

[Mooseman]