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The mkiv Supra Owners Club

Air conditioning


FCorps

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Hi, as we are approacbhing summer I need to get my long non-working air con looked at - anyone got any experience on whether they are repairable /replaceable etc.

 

Are the spares/replacements easy to get hold of, anyone North London who specialises

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Air conditioning is just like your fridge in reverse so its not especially complex or complicated. It has a compressor, a condenser at the front of the car where the refrigerant liquifies under cooling and pressure (from the air flow and compressor) then an expansion valve leading onto the evaporator inside the car when the refrigerant turning from liquid to a gas removes heat, effectively cooling. Its not rocket science stuff. 

You need first to check your system can hold a vacuum. If it can, great, your plumbing is all good. You then need to see if the compressor works, there are a few aspects to that. The A/C switch to send power to the clutch and the sensor which is pressure regulated. No pressure then no clutch. No power then no clutch. Until the clutch engages you won't get the compressor running. You don't need a full charge of 600g of R134a to persuade the compressor to fire up. 7psi on the suction side of the compressor, the low pressure side, will keep a compressor running. An idle system will sit around 50psi. A running system will be a little over 1 bar positive pressure on the suction with running compressor.

If the clutch doesn't engage when you have pressure in the system then it is either the clutch or sensor not working. the clutch can be hot wired to be always engaged which will help pinpoint where problems lie.

If your system hold vacuum and pressure then it is a simple fix to get up and running again. Most expensive repair will be a new compressor. If it doesn't hold pressure then you have a leak so first task is adding UV dye to track the leak down. If its a core failure you'd be in trouble as Toyota no longer supply parts for the A/C. If it is a pipe leak then any good A/C engineer can mod up a new pipe. 

You don't need any particular A/C specialist to diagnose your problem(s). Armed with a set of pressure gauges and a vacuum pump will tell them pretty much all they need to know. As a final point to note, R134a is being phased out and is no longer used in new vehicles. This has two impacts, one is pricing and the other is reducing availability that feeds back into pricing. So, R134a is getting very expensive (currently around 10 times the cost it was 20 years ago). So, you may want to consider other gasses rather than going with R134a. Some of those are hydrocarbon blend (mainly butane) flammable and some are like R134a, non-flammable HFC's.

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