Air Con 3008 - is it Coping? Or something else?
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Thread: Air Con 3008 - is it Coping? Or something else?

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    Default Air Con 3008 - is it Coping? Or something else?

    The performance of my aircon on a hot day seems to die as the journey gets longer. Is this a case of an aircon not coping with the heat given out by the occupants, heat leaking in through the moonroof (closed still!) and the windows in the car? It seems to work ok on start of the journey. Could it be a case of an under charged aircon system?

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    Are we talking about the 40 deg or so days we have had lately? In those you'd never get the car down to the low 20s, and the longer you are out in the sun, the harder it is. The compressor output also is related to engine rpm. Condenser coil performance depends on air flow and temperature..

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    Try your air con on recirc and see how you go.
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    ok thanks, i did have previous login, but for some reason it stopped working some time ago,hence analysis, the only one i use. cheers robert

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    Tried recirc as well. Will get it checked by the aircon specialist. (More $$$$s.. :-( )

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    Just a side note. Humidity seems to be a major factor as well. A lot of "air con power" goes into removing the humidity in the interior air.

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    It does indeed. We need to cool hot humid air containing much vapour to the point where the vapour (a gas) becomes water, and drains away. It consumes power. Air conditioning calcs are done on what is called a psychrometric chart, which you can look up online. Tracing lines on the chart between the start point (outside humid hot air) and the desired end point (in the car) will show what is required.

    The suggestion to recirculate is to remove much of the dehumidifying from the problem. After a while the start point is much closer to the desired end point, and you are mainly transferring to the front of the car the solar heat coming through the body.

    Since the power input to the system is engine belt driven, it is very variable, and rarely optimum.

    Chart is here- https://upload.wikimedia.org/wikiped...vel.SI.svg.png
    Last edited by seasink; 23rd January 2016 at 08:54 PM.

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    Quote Originally Posted by french-car-newb View Post
    Just a side note. Humidity seems to be a major factor as well. A lot of "air con power" goes into removing the humidity in the interior air.

    Could the evaporator be icing up?

    This could be caused by

    1. Blocked pollen filter reducing air flow across the evaporator - you do change your pollen filter every 12 months or so?

    2. Refrigerant gas getting low

    "if there is some refrigerant but not enough the coil may become abnormally cold, freezing the condensate that forms on the cooling coil surface as moisture condenses out of air moving across the coil. This freezing condensate liquid can form frost and may build up into a coil icing problem or frost may appear on the cooling coil's refrigerant suction line."
    http://inspectapedia.com/aircond/Cooling_Coil_Frost_Ice.php#CoilIce

    I am pretty sure my Landcruiser has the same problem - I really must get the gas pressure checked!

    Cheers

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    If you decide to get it checked find an a/c guy who'll recharge it with Hychill (sold by Bursons).

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    Quote Originally Posted by dvr View Post
    If you decide to get it checked find an a/c guy who'll recharge it with Hychill (sold by Bursons).
    Respectfully suggest that may not be a good idea for a vehicle designed for R134A.

    I'd use what the manufacturer recommends.

    I'd only ever use Hychill -30 in a system designed for R12 , which or course, is now NLA.

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    HyChill - Home

    Call them if you're unsure. I did and use it in two cars to replace the R134a. Cooler and stopped leaking, I'm happy with it.

    Lots of old info on this forum about it too.

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    Quote Originally Posted by dvr View Post
    HyChill - Home

    Call them if you're unsure. I did and use it in two cars to replace the R134a. Cooler and stopped leaking, I'm happy with it.

    Lots of old info on this forum about it too.
    I still would not use in a R134a designed car. The temperature -pressure curve of -30 is quite different To R134a. So the TX valve will be undersized.

    And R134A is safer

    Perfectly fine to use in R12 designed vehicles, for which is it a drop in replacement. If you are happy to accept the risk.

    http://hychill.com.au/products/minus-30

    The wording of the compatibility sounds a bit vague to me...

    And it's very flammable as Dr Iain Maclaine Cross (Hychill's engineering consultant) demonstrated.

    https://www.youtube.com/watch?v=k0K1WPCWm2k

    Watch the clip right through and then think about the safety of propane/ butane refrigerants.

    TBH I was an early supporter of -30 and lost my mojo after having an incident with leaking flare and arcing plug lead. Fortunately in an engine bay and outside my workshop. It is not easy to extinguish LPG, even at low side pressures
    Last edited by robmac; 24th January 2016 at 01:44 PM.

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    Just shows how safe it is.

    He took the concentration to extremes. Being heavier than air if there was a leak in the cabin only the gas above the leak would escape. The rest would settle below the leak. It also has a smell and when opening the door to get in a lot would fall out. I'm more afraid of the 70 litres of fuel behind me, than 200-300grams of Hychill in my a/c system.

    Its use in this country is more extensive than what you would think. Oka have used it as OEM for several years without any incidents.

    Anyway all the info's available. For those contemplating using it they can make up their own minds.

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    The main market for Hychill -30 product is the DIY market and those that don't have a refrigerant handing license.

    I'm not against using the product to replace R12. Provided the risks are evaluated.

    But when the system is designed for R134A there is no real reason not replace like with like. Unless the technician doesn't have a refrigerant handlers licence.

    Who is OKA - OK they are small Australian company that design 4wd and Off road vehicles which are largely manufactured in India.

    Current name is Reymer P/l
    Last edited by robmac; 24th January 2016 at 02:48 PM.

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    Design engineers actually know a bit about what they do, and component makers spend a fortune when designing things like mass produced AC systems. Then every backyard mechanic knows better, whether AC refrigerant, suspension, exhaust, etc. A cynical comment I admit, but I would not change refrigerant to something not envisaged at the component design. Unintended consequences tend to happen.
    robmac and Whippet like this.

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    To return to the core topic, it's worth understanding that modern, variable displacement air conditioning compressors run constantly when the AC is "on". This opposes old style compressors which didn't clutch on until the pressure switch dictated.

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    We have a VE Commodore that did the same thing. Air con started out cold but progressively lost its cooling. It was worse (happened quicker) on hot humid days. As little as 30 mins to the point where it was hardly worth having on. When I noticed that the condensate puddle on the garage floor was much bigger than normal, I started to do some research. Took a while to pin down, but the cause was the temperature thermistor was placed a little to far away from the evaporator. The control signal sent to the computer said that the Evap was warmer than it really was. It would attempt to rectify by allowing more gas to flow through the Evap which led to icing up. The icing would all but completely block airflow. So it was actually trying to be too cold. Thermistor placement was apparently critical within a few mm.

    The dealer repositioned the thermistor and all was fixed. Turns out it was a known problem, although we were amongst the first wave of customers to complain.

    And a comment on HYCHILL. I converted the CX and got reasonable results. I did the research and bought all the gear. I was comfortable with the safety aspect. You are dealing with a small amount of gas and the real risk of fire is minute. But the CX had inadequate air-con by design. So it needed all the help it could get.

    If the air-con in a modern car is not working, the problem will be a leak or something to do with the control system. Not the actual gas in my use. Find and fix the problem before you even consider changing the gas.
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    I haven't looked up what is in a 3008, it may be smaller, but this graph shows the performance of a variable displacement car ac compressor, and how output varies with the pulley rpm.
    Air Con 3008 - is it Coping? Or something else?-compressor.jpg
    The system is designed for this large variation.

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    Quote Originally Posted by addo View Post
    To return to the core topic, it's worth understanding that modern, variable displacement air conditioning compressors run constantly when the AC is "on". This opposes old style compressors which didn't clutch on until the pressure switch dictated.
    Are you sure old style compressors would clutch in and out based on temperature? I thought they would mix cold air from the evaporator and hot air from the coolant. A waste of energy I know - but this was my observation.

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    Quote Originally Posted by seasink View Post
    I haven't looked up what is in a 3008, it may be smaller, but this graph shows the performance of a variable displacement car ac compressor, and how output varies with the pulley rpm.
    Click image for larger version. 

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    The system is designed for this large variation.
    Very informed educated replies.

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    Quote Originally Posted by Rob T View Post
    We have a VE Commodore that did the same thing. Air con started out cold but progressively lost its cooling. It was worse (happened quicker) on hot humid days. As little as 30 mins to the point where it was hardly worth having on. When I noticed that the condensate puddle on the garage floor was much bigger than normal, I started to do some research. Took a while to pin down, but the cause was the temperature thermistor was placed a little to far away from the evaporator.
    I do see similar puddles even with short trips. I am not sure the thermistor can be placed "where every you like". The thermistor was replaced a year ago and that time it was faulty and the air con was not working at all. This problem seems to be different as the air con does cool but not quite useful as in your case.

    From my observation (during my marine engineering days at sea) was that an overcharged system would cause icing before the evaporator and an undercharged after the evaporator. Of course there are optimum high pressure and low pressure parameters for any refrigerant or air con system.

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    Quote Originally Posted by french-car-newb View Post
    Are you sure old style compressors would clutch in and out based on temperature? I thought they would mix cold air from the evaporator and hot air from the coolant. A waste of energy I know - but this was my observation.
    It was not strictly temperature as pressure that called the shots. Pressure critically low meant the compressor never clutched in, pressure too high and it clutched off, they only pulled in when within acceptable high side ranges. The TX valve allowing more or less compressed refrigerant flow, effectively controlled this pressure at the switch. Now there's still a high side pressure reading to the AC control module but the decisions are usually made remotely based on the value returned.
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    Quote Originally Posted by addo View Post
    It was not strictly temperature as pressure that called the shots. Pressure critically low meant the compressor never clutched in, pressure too high and it clutched off, they only pulled in when within acceptable high side ranges. The TX valve allowing more or less compressed refrigerant flow, effectively controlled this pressure at the switch. Now there's still a high side pressure reading to the AC control module but the decisions are usually made remotely based on the value returned.
    Yes that makes sense. I was talking of temperature control in oldish cars where you have just one dial. Turn left it is max cool and turn right max hot. Anywhere other than max cool it would open the flow of hot water coils to the air intake.

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