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Following a very costly surgery, I'd love to save several hundred bucks with a DIY kit for the car's AC system. A recent shop diagnostic discharged the line and also determined a leak near the high side valve, but they let me know it will be around $400 USD to replace the hose and recharge the system.

Hoping I could pick the brain of the community here with 3 questions as I consider investing $150 USD instead into a DIY kit:

  1. With the line being discharged, does this mean I would need the line vacuumed to remove atmospheric air (moisture) before I use a DIY recharge kit? Would a drying additive work instead of vacuuming? Or is this something that can wait and be checked on later?

  2. Regarding the leak, the DIY kit optionally includes an aerosol-based leak sealer (provided the leak is small and repairable in this way). Product info says the sealer is moisture activated: so would this mean I should use the sealer 'before' using a drying additive/vacuuming the line? Afterward?

  3. If the above additives are a good idea, I believe they are to be added before the r134a-equivalent ("12a") recharge kit (and then I would tally the amount of grams/ounces provided by additives (1) and (2), and then subtract that from the amount needed from the r134a-equivalent (12a) kit. But it's hard to find info on how to calculate the weight... am I to use a scale? (Saw a guy doing this online)

The kits are actually 12a which people keep telling me are the "same" as r134a (provided that you convert the math correctly)... but if that produces red flags I'd love to hear your all's thoughts on that too.

Appreciate the help immensely and look forward to reading your comments - thanks!

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  • Products mentioned in links below: Drying additive (mentioned in 1): REDTEK Dry12 A/C Dehydration Treatment 4 oz. can... Sealing additive (mentioned in 2): RED TEK ProSeal12 A/C Seal Treatment 4 oz. can... And r134a-equivalent kit (mentioned in 3): Another brand is available at my auto parts store but same idea as: REDTEK A/C Refrigerant 6 oz cans & Installation Hose w/Gauge - 2 Cans
    – Fig Newton
    Commented Jul 7, 2022 at 20:04
  • Magic sealer probably won't work. The leak needs to be found and fixed. The one I repaired turned out to be 2 cracked "O"" rings where the two lines connected to the compressor. Then the cost new rings was less than a dollar. I evacuated , refilled with refrigerant, with no magic additives ; It ran fine for years. Commented Jul 7, 2022 at 22:00
  • Lol thanks for looking out for me @user-whose-post-disappeared. Nope, that's why I ask, don't want to make a bigger problem, which in the end would be the complete opposite of cost savings. So yes the shop discharged the R134A, and the DIY kits are indeed 12A (I didn't clarify that until the end of the question)... but all in all this is a bigger subject than the kits make it out to be, so I appreciate everyone's advice. I had a hunch it might be a good idea to ask first (rather than afterward!)
    – Fig Newton
    Commented Jul 8, 2022 at 5:56

1 Answer 1

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It sounds like you have a serious case of the cheap's, and I think you know how that tends to turn out.

It is an offence for unqualified people to handle most refrigerants.

With the line being discharged, does this mean I would need the line vacuumed to remove atmospheric air (moisture) before I use a DIY recharge kit?

Yes, it does mean that. In order to service an A/C system, you must pull a vacuum to remove all gases that are not the correct refrigerant (so basically: all gases). It is also absolutely essential to remove ALL water.

So you will need an A/C vacuum pump and a gauge set. This is not optional.

Are you sure you want to do this?

The latest trick I have seen in DIY A/C servicing is to draw a vacuum, then charge the system with canned nitrogen. Nitrogen is harmless, and does not hurt the system. Then, they hold the pressure on the system for awhile to confirm they have abolished all leaks. If it has failed, they vent the nitrogen and keep repairing the system. Once the system is tight, they take it to the pro to have freon added, or they use a DIY-legal refrigerant.

Would a drying additive work instead of vacuuming?

LOL no, that will not work.

Or is this something that can wait and be checked on later?

I don't see how. Even if you pressurize your system with something else for testing, you'll need to get and keep water out of the system.

I suppose you could pressurize the system with nitrogen just to make sure you've solved the leak problem, and then take it to the mechanic to have them vacuum it and recharge it with Freon, but that will still be a hefty bill.

Make sure to tell them it's nitrogen so they don't try to recover the nitrogen lol.

If the above additives are a good idea

LOL they're not. They're marketed as a "Hail Mary" play to people whose A/C just isn't going to work at all without them. The problem is, if they're moisture-activated, well your system is chock full of moisture, and everywhere there's moisture, that stuff will turn solid. That will be many parts of your system that don't respond well to having solids in them. It could do much more damage to your system, destroying all hope of ever fixing it.

I wouldn't touch any of that stuff with a 10 foot pole. As always, if it worked, the OEM would use it.

It's really that simple, forget those conspiracy theories about the manufacturer holdng out on us with secrets. The only thing the OEM cares about is the car making it through the warranty period uneventfully. They'll use any tech THAT WORKS, and no tech that doesn't work.

I believe they are to be added before the r134a recharge kit

It's illegal for you to use R134A. You do not have the certification, special recapture equipment, or supply relationships to get the recaptured stuff destroyed (or re-refined and reused; reuse is now the ONLY source of R22 for instance).

The kits are actually 12a which people keep telling me are the "same" as r134a (provided that you convert the math correctly)... but if that produces red flags I'd love to hear your all's thoughts on that too.

Propane is R290. It's actually awesome because it's non-ozone-depleting so it's legal to DIY. No cert, no recovery pumps. Only problem is, it's flammable. Same is true of R600a (isobutane). Your "12A" is a mix of those two, designed to behave like R12. Neat idea, but your system is tuned to R134A.

Every refrigerant has different ideal pressures, different vapor points, different latent heat. The system has to be designed and tuned for the refrigerant. R12 and R134A are different, and required redesign of A/C compressors and expansion valves. If you change refrigerants it won't perform as well. Well enough for you? Maybe.

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  • Thanks @Harper, gotta tell you this is so valuable. Ha, a simple case of the cheaps sounds like a dream, but it happens to be a case of the brokes :-} after three huge medical surgeries which couldn't be avoided. The timing of the AC is just bad as it happens to be summer but with a family member with pretty serious heat intolerance. Definitely don't want to make things worse or more expensive by a DIY job gone bad, so I appreciate you taking all that time to write here.
    – Fig Newton
    Commented Jul 8, 2022 at 6:28
  • While I agree with pretty much everything you've said, the part about "It's illegal for you to use R134A" confuses me, as I can go down to the store and buy a can of 134a, no questions no certifications needed. I have a can on my desk right now.
    – Glen Yates
    Commented Jul 8, 2022 at 22:47
  • @GlenYates sales because of an exception. The exception DOES NOT nullify the other rules, requiring non-venting and refrigerant recovery. Commented Jul 9, 2022 at 7:55

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