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Disco 3 (LR3) AC Hack? Help!

Discussion in 'Land Rover Discovery' started by Charles Banbury, May 21, 2020.

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  1. Charles Banbury

    Charles Banbury Member

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    So, my discovery 3 2007 HSE with rear AC went warm. I took it to a chap who is a lifetime AC guy now semi retired to have a re-gas. He vacuumed the system, did a test, checked everything, including the rear setup, added dye and concluded there was a potential tiny leak in the evaporator. He Re-gassed the system and everything worked. However, he warned that it was not a complete fix. Today, (2 months later) it’s failing again. The car is a truly immaculate vehicle full and complete LR history and just shy of 150k (belts and water pump done) my thought is that the gas has dropped to a level that prevents the compressor from doing its job and to fix the evaporator will be very expensive. So, my thought is to buy a canister of refrigerant and just top it up every few months. Is this a mad idea? I am a scientist so understand the gasses but not a mechanic and unsure how to pressurise the system. Basically, which valve should I connect to? High or low pressure? Could anyone send me a picture of the correct valve? With that info I could probably sort the rest out.
    Any advice or help would be excellent.
    Many thanks.
     
  2. freelance

    freelance Well-Known Member

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    A scientist? But you’re happy to release air con gas into the atmosphere via a leak ?
     
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  3. biketeacherdave

    biketeacherdave Well-Known Member

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    Oh dear
     
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  4. Charles Banbury

    Charles Banbury Member

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    Fair enough, you are quite right. Get it fixed properly. Good call.
     
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  5. Avocet1

    Avocet1 Well-Known Member

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    I take it you have checked to see what sort of a job it is to change the evaporator? Is it really that bad a job?

    To answer your question, most aircon systems have a pressure switch in them which cuts the power to the clutch on the aircon pump if the pressure drops below a certain threshold. This is to protect the pump (which can be damaged if run without enough refrigerant in the system, because the lubricating oil is dispersed in the refrigerant.

    It is very rare for an evaporator to leak, as they're so well protected from damage and the elements. It is usually the condenser that cops for it first. However, it's possible for the o-ring seals in the pipe unions to fail. Might be worth getting a second opinion if it's a big job.

    Environmentally, R134a (your refrigerant) is much more benign than the stuff it replaced (R12), which was a vicious ozone depleter. R134a is OK for the ozone layer, but is a greenhouse gas about 1400 times worse than CO2. However, it's worth keeping things in perspective. If your car averages (I dunno, say), 200g/km of CO2 and your aircon system takes (say) 800 grammes of refrigerant, then total loss of all your refrigerant will have a global warming potential of (say) 800g x 1400 = 1120000g of CO2. That, in turn, is about the same amount of CO2 as you'd create by driving it about 5600 miles. (You can get more accurate figures for CO2 emissions from your fuel consumption, and there might be a sticker under the bonnet saying R134a and quoting the mass of gas needed for a recharge, in grammes).

    The recharge bottles are expensive (about £50 with a £10 deposit on the bottle) plus about £20 for the connector and gauge to connect the bottle to your aircon system. Simple to use, the high and low pressure ports are different sizes, so the connector will only fit on one of the ports (the low pressure one). However, they're not as good a solution as a proper regas.
     
    Last edited: May 21, 2020
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  6. Henry_b

    Henry_b Rover V8 Powered

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    [​IMG]
     
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  7. gstuart

    gstuart D3 Grandad

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    hiya

    the system indeed has a low pressure switch that will turn it off, personally wouldn’t keep topping the system up

    normally the pipes that are near the passenger side wheel are capped off to disable the rear AC

    funny enough it’s normally the rear pipes that leak, haven’t heard of a rear evaporator leak before

    don’t know how expensive they are , cheaper of course if u do the work urself, if the system is empty can then do the work and get ur mate to redo a vacuum/ refill



    hope that helps
     
  8. gstuart

    gstuart D3 Grandad

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    Just checked , rear Evaporator are £230.00
     
  9. lynall

    lynall Well-Known Member

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    Yes you can bodge it as you say, but I would spend a few quid and find the leak, not guess but find the leak, as you have rear a/c it will be one of two things going, 1 the condenser rad, or more likely the rear a/c alloy pipes that run along the passenger inner sill.
    Most a/c guys will pressurise the system with nitrogen and go around with their soapy water botttle looking for the leak.

    You can buy reifll gas cans with a gauge, you can refill via either port, the refill can will have the fitting on it.
    You can also buy cans of R134 with leak sealer built in.
    The models with rear a/c hold a lot of gas 850 grams Iirc
    The alloy pipe sections for the rear a/c are expensive, circa 150 quid per section, and there are four of them.
    If it is the rear pipes, the cheap dodge is to fit the std front a/c only pipe for about 70 quid.
     
    Last edited: May 22, 2020
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