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Messing around with Red Tek r12a A/C recharge - not getting anywhere

Discussion in 'LH: Large Cars, 1993-2004' started by MoPar~Man, Jun 20, 2015.

  1. Tomguy

    Tomguy Well-Known Member

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    Making the system last longer is a worthwhile endeavor. After my evaporator sprung a leak in 2011, a mere 12 years after the car was built, I replaced it, vacuumed the system down, and re-filled with R134a and I'm dreading the day I need to do the job again. It's only been 7 years without having to add a drop of refrigerant or touch the system.

    While you can tout the benefits of a swap to a non-factory refrigerant, the fact is that its benefits of being in an R12 system aren't there in R134a systems. R134a systems are designed with parallel flow condensers, expansion valves (in the case of the 300M) designed for R134a (not R12 or R12a) pressures, and a swash plate compressor built for R134a. When swapping from R134a, for optimal cooling, the expansion valve would need to be replaced, or else the evaporator will freeze (likely the real reason a converted system shuts off more, because the temp sensor in the evaporator says it's a chunk of ice and needs to defrost).
     
  2. manybrews

    manybrews Well-Known Member

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    I’m kinda confused by the post.
    At first it seems you think extending the life is good, then you say it’s not worth it.

    But it is worth it, particularly in a r134 system. Because r134 is not a very good refrigerant.
    And it is harmful to the environment.
    And it can be damaging to the system if any moisture manages to enter.

    It condenses poorly, hence the reason for increased efficiency condensers. But these also will benefit any refrigerant you use.
    You’re right about the evaporator freezing, and I’ve already touched on that. But most cars today already use thermal control of the evaporator to prevent freeze up. They have to, because modern AC systems work so well that any of them will freeze if allowed to run constantly. Any of them. That’s always been a problem with ac systems, and there have always been some way to prevent that from happening.

    The improved cooling of the evaporator using HC refrigerant allows the system to shut off more frequently.
    That’s the entire point of thermostatically controller evaporation. The load on the evaporator is always changing due to ambient conditions, required cooling or dehumidification, etc. it may never shut off on 100 degree day. It may barely run on a 70 degree day.
    The evaporator will freeze with 134 refrigerant as well. It just takes longer.

    I personally don’t care what anyone uses for a refrigerant. But I do want people to know the benefits and drawbacks of each.
     
    GLHS60 likes this.
  3. Tomguy

    Tomguy Well-Known Member

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    The benefits and drawbacks are what I'm trying to outline as well. We're on the same page with the goal, where we differ is the science behind the scenes. From the FSM:

    "High-pressure, high temperature liquid refrigerant from the liquid line passes through the expansion valve orifice, converting it into a low-pressure, low-temperature mixture of liquid and gas before it enters the evaporator coil. A temperature sensor in the expansion valve control head monitors the temperature of the refrigerant leaving the evaporator coil through the suction line, and adjusts the orifice size at the liquid line to let the proper amount of refrigerant into the evaporator coil to meet the vehicle cooling requirements. Controlling the refrigerant flow through the evaporator ensures that none of the refrigerant leaving the evaporator is still in a liquid state, which could damage the compressor."

    R12 (and thus presumably R12a designed to replace R12) is still a liquid at the higher pressures that an R134 evaporator and its expansion valve are designed for. In other words, R12 (and R12a) will still be in liquid form and thus can hydrolock the compressor in a system where the expansion valve wasn't changed out. A system with an orifice tube (A "Dumb" / cheap control system) may not be as effected as it's a fixed venturi that controls the flow and is passive, IE it depends on the physical properties of the fluids passing through it and is self-regulating in that manner.

    I'm not arguing about one being better in general versus the other. I'm saying that R12a is not a suitable substitute for a 300M's AC system for several reasons. I'm sure it's fine (and likely superior) to R134a in systems designed for R12. I will admit I've never played around with anything other than R134a. When my R12 system in my 1992 XJ Cherokee died, I grabbed the compressor, condenser, expansion valve, and all the lines (including the attached dryer I replaced) from a 1995 R134a Cherokee, and converted the system after flushing the evaporator thoroughly.
     
    GLHS60 likes this.
  4. manybrews

    manybrews Well-Known Member

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    I understand your concern.. but that’s not really how a refrigerant system (at least in a car) works. At least in regards to the three refrigerant types were taking about.

    The 3 refrigerants (r12, r134, r12a) all have pretty similar boiling temperatures and pressure/temperature points. R134 generally has higher high side pressures because it’s reluctance to condense, but that’s about it. Hence the reason for high efficiency condensers.

    The evaporator (low) pressure side of all three is almost exactly the same. Within 10 psi dependent on ambient temps, so the functionality of the system is basically unaffected.
    An evaporator from an r12 and r134 system should be practically identical.

    So the r12a and r134 boiling point is close enough that system redesign isn’t needed.

    As I said, I don’t really care what refrigerant people use in their systems.
    But if you have a r134 system that is subpar (particularly in high temp areas), switching to r12a would reap benefits due to its improved heat removal and condensering capabilities.

    Of course, it’s all moot for most people since very few know how refrigeration works and shouldn’t be touching theirs anyway!
     
    GLHS60 likes this.
  5. MoPar~Man

    MoPar~Man Active Member

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    Hi guys. I'm just jumping in here (haven't been here for a while). I started this thread way back (I guess 2015). Just wanted to say I haven't touched the AC system in the past 4 years - and it's still working great. Gives me very fast defogging / defrosting in the winter and great cooling in the summer.
     
  6. GLHS60

    GLHS60 Well-Known Member

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    But, but, you contaminated the system !!!

    LOL

    Red Tek is a winner...

    Thanks
    Randy
     
  7. manybrews

    manybrews Well-Known Member

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    Glad it still works.
    I had to jump into this older thread because I feel as though HC refrigerants get ignored due to nonsense government lobbying and false information.
    People that THINK they know ac systems will scream “you just made your ac system into a bomb!” if you tell them you have used an HC refrigerant. They apparently don’t realize HV refrigerants are used in 50% of the worlds cooling systems and work better than any other type of refrigerant, period.

    They also seemingly ignore that the fuel tanks in their cars have 150-200 pounds of highly volatile HC fuel rolling around which is combined with oxygen! So I snicker at how they can think that 6-10 ounces of HC in a closed system is somehow a rolling time bomb.

    I’m glad your red tek conversion worked and is still working; it’s simply one of the best choices out there for older cars and for people that understand how an ac system is supposed to work. Or for systems that have mediocre hvac systems to begin with.
    All my cars are converted to r-12a and they work incredibly regardless of what they came with.
     
    ka9yhd likes this.
  8. GLHS60

    GLHS60 Well-Known Member

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    I wouldn't have functioning A/C on my 1986 Omni, 1986 Chevy van, 1989 Voyager or 1997 Astro Van if not for Red Tek!!

    Thanks
    Randy
     
    manybrews likes this.
  9. GLHS60

    GLHS60 Well-Known Member

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    Some American friends on another forum are using Dust Off Electronics Duster as refrigerant.

    What will they think of next!!

    Thanks
    Randy
     
    RalphP likes this.

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