HELP: How many cans of R134a?

[mmadlang]

Hi,

I just evacuated my A/C. How many cans of R134a do I need on my A4 2.0T 2007? Do you all know what pressure on high and/or low side should I be aiming for?

Thanks!

[DRAKLORE]

Ugh, just please take it to a shop. I've had to replace to many ac components because people thought they could get away with using that stuff :-/ don't get me wrong it can be done. You have a tag probably on your upper grille or hood that will have your a/c systems capacity in ounces or another format. But if you didn't completely remove all of the freeon then you will be shooting in the dark.

Biggest reason why I hate those cans is because most contain a stop leak component which WILL gum up your compressor, condensor, and lines mainly the inline thing(god it's been to many years lol) but yea don't do it :-/

[xKrNxBoix]

Ugh, just please take it to a shop. I've had to replace to many ac components because people thought they could get away with using that stuff :-/ don't get me wrong it can be done. You have a tag probably on your upper grille or hood that will have your a/c systems capacity in ounces or another format. But if you didn't completely remove all of the freeon then you will be shooting in the dark.

Biggest reason why I hate those cans is because most contain a stop leak component which WILL gum up your compressor, condensor, and lines mainly the inline thing(god it's been to many years lol) but yea don't do it :-/

I second that... I also had leaked all my freon on my A4 and thought it was okay to use those cans to fill it up.

Trust me, if you leaked all or most of the freon, it would take alot of those r134a cans to fill it up to optimal level. First, it won't even be cost efficient. Second, you need to vacuum all the old freon out first before filling it up again. Thirdly, those r134a freons and the gauge supplied are awful. I believe I paid around $200 for labor and freon. Get it done right at a shop.

[mmadlang]

Thanks for all your concerns! My A/C's better now. Here's what I did:

DISCLAIMER: Although I was supervised by a certified mechanic, I'm not a mechanic in any shape or form, so follow the information below at your own risk. If you can, just get your car to the shop. I did this, since I have time, and someone looking over my shoulders. :)

1. Rented A/C Manifold Gauge Set from Autozone (Free, just put a refundable deposit).
2. Rented 2.5 CFM A/C Vacuum Pump from Autozone (Free, just put a refundable deposit).
3. Bought a gram scale from Harbor Freight.
4. Bought 2 cans of R134a without additives.
5. Looked at the A/C's capacity under the hood of the car; mine's 500g.
6. Evacuated the system, but hooking up the A/C Manifold Gauge Set to the system, and the A/C Vacuum Pump to the manifold.
7. Checked for leaks, but turning off the vacuum pump, close the manifold valves, and waited for 10 minutes.
8. STOP HERE IF THERE'S A LEAK. THE FOLLOWING INSTRUCTIONS BELOW WILL BE USELESS IF THE AC's LEAKING.
9. If the low-side gauge needled didn't move for 10 minutes, it's a good assumption that there's no leak.
10. Vacuum the car for more that 30 minutes. I didn't do this, but some folks in the Internet vacuumed it for 24-hours to make sure moisture's out the system.
11. Close high and low valves of the A/C Manifold Gauge Set.
12. Weigh the can with the R134a Can Tap Valve-Screw-On in grams.
13. Screw the R134a Can Tap Valve-Screw-On to the yellow line of the A/C Manifold Gauge Set.
14. Release the valve of the R134a Can Tap Valve-Screw-On to release the refrigerant to the manifold set.
15. At this point, there's no refrigerant going to the car's A/C system yet.
16. To make sure there's no moisture and air on the manifold set, release a little bit of refrigerant by loosening the end of the yellow line in the manifold set. It's the end that's attached to the manifold gauge. As soon as a little bit of gas gets released, close it back.
17. Boil water in a pot.
18. Turn on car's engine, and set the AC to LO. At this point, ECON might be lit up. The reason is that the car detected that there's no refrigerant in the system, and turned off the compressor to avoid damage.
19. Open the LOW side of the manifold gauge, releasing refrigerant to the system.
20. Slowly submerge the R134a can to the pot with boiling water. This will help the refrigerant go in the system. I found out that this is needed in the car since the compressor is turned off. I think there's a way to short circuit the compressor to force it to engage, but I didn't go with that route.
21. While trying to fill the system with refrigerant, also look at the low side gauge and make sure the needle's turning clockwise. Note, sometimes the needle will drop. This is normal, the refrigerant traveled to the car's A/C system and the pressure eased. As long as the general direction of the needle is clockwise (increasing), this means that refrigerant is entering the system. You can also feel the metal fitting near the Can tap valve, and it should be cold.
22. If the can's very light, close the low-side valve AND the R134a Can Tap Valve-Screw-On.
23. Remove the yellow line from the R134a Can Tap Valve-Screw-On; leaving the R134a Can Tap Valve-Screw-On on the can.
24. Weigh the can and the R134a Can Tap Valve-Screw-On on the gram scale.
25. Do this math. Original weight - Final weight - 57 grams
26. 57 grams is 2oz that is wasted by releasing a little bit of air and gas that is in the manifold gauge hoses. I found this value in the Internet.
27. EX: 716g - 409g - 57g = 250g
28. Since my car needs 500g, I need 250g more.
29. I added another can of R134a, and did the process again starting from weighing the R134a can with the R134a Can Tap Valve-Screw-On.
30. The value that you're trying to hit is 500g. Since we're dealing with crude tools. We can miss plus/minus 50g, it's noted in the hood of the car.
31. This means that for 500g capacity, you should not exceed two R134a cans. Those cans are rated 356g.
32. FINISH:
33. TIP 1:You might need to turn the ignition on and off in the middle of filling up the 2nd can. This helped me engaged the compressor, and turning off the ECON LED.
34. TIP 2: Your air coming from the A/C vent should start cooling in the middle of the 2nd can fill. NO TEMPERATURE CHANGE SHOULD HAPPEN ON THE FIRST FILL, COMPRESSOR IS STILL TURNED OFF.
35. TIP 3: You might find out that refrigerant is not entering the system. Please double check the line fitting, and make sure it's working properly. For me, I discovered that the manifold gauge set that I rented is defective.
36. TIP 4: Make sure that the low side and high side ports are connected to the manifold fittings well. Mine had a leak, and discovered it when I tried to vacuum, and turn off the vacuum pump for 10 minutes. I thought my A/C system had a leak, it was just the fittings to the high and low side ports.

[DRAKLORE]

Good writeup, and good luck...
Tho I hope you saved some considerable amount of money, just saying we never charged that much to recharge an a/c system I think 40-60$ and then you'd have someone elses name on it, there time and their tools.. And their know how.
But if your happy with your results and you saved 20$ good for you.

[Stewy]

Wow, great write-up. But I agree with what's been said above, pay the small amount of money and have a certified shop re-charge it for you.

[mmadlang]

Thanks Stewy and Draklore! I strongly agree. I will not recommend this procedure if you know that your car's leaking, or you replaced a component. The reason is that the tools I used are not enough to totally evacuate moisture out the system that has been repaired or components replaced. Professionals will do multiple stages of evacuation, vs single-stage. Some will pump nitrogen into the system to remove the moisture out. They actually have special tools to precisely know the weight being pumped in the system, and make sure that the oil in the compressor is enough.

Having said that, if you want to save, or want to learn more, then one can follow the procedure for simple refrigerant replacement. Instructions came out an HVAC book, with supervision from a mechanic friend.

NOTE: Please don't release the refrigerant into the atmosphere; save the Earth.. :) Don't be like me who accidentally released it to the atmosphere by unknowingly unhooking one of the ac tubes.. :(

Thanks!

[fly300kts]

So, is your AC finally working? Was I right ...again

Phil

[mmadlang]

Yeah, AC's working great again!

Not to jack my own thread... but thanks Phil for selling me the bumper removal tool, and DIY timing belt. Saved me a lot of mulla, and learned a lot about my car! I tried giving a positive feedback on your DIY, but I don't have write privileges on the Tech forum.

So, is your AC finally working? Was I right ...again

Phil

[fly300kts]

No worries Man, it was my pleasure

Phil

[aa2by2]

a little off topic but

hello
i am topping off the R134a in my 2010 audi a5

on max ac, with recirculation, 90 degrees F ambient, the center vent cant get down to 39 degrees F. which is great
however, the low side pressure only gets up to 28 psi. the chart indicates that the low side pressure should be 45 psi.

hence: low side pressure too low, but center vent temperature ok

question: does the system still need more R134a?

[onedumslack]

a little off topic but

hello
i am topping off the R134a in my 2010 audi a5

on max ac, with recirculation, 90 degrees F ambient, the center vent cant get down to 39 degrees F. which is great
however, the low side pressure only gets up to 28 psi. the chart indicates that the low side pressure should be 45 psi.

hence: low side pressure too low, but center vent temperature ok

question: does the system still need more R134a?

If you're not having a temp problem then I would not add any more. Psi is relative to the ambient temp outside. There is no set pressure unless you have a set temp. The only way to tell you have the correct amount without calculating for temp is to empty the system and meter the correct quantity back in.