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[philayl]

Hi All, the air con does not blow very cold air out. I took it to be checked to Halfords, they said it was o.k. it did not need gas. The engine note changes when you switch between eco and air con on, so I assume the compressor is working, the air temperature changes from hot to cold if you alter the setting, so I assume the flaps work as well. I know the gas has never been changed since the car was new, could this be affecting it, does the gas need changing or is it a case of if there is gas there it should work?

[Matchless]

Engine note change indicates that the compressor is starting up but check under the bonnet, front face of compressor pulley should be spinning when 'on' not just the pulley rim.
Only needs 30 psi for compressor to switch on and that isnt enough refrigerant to produce any cooling. Did hafords give you any system pressures or empty and refill the system with 950g of refrigerant?

[philayl]

No, just connected a lead on a can to the system and said it is in the blue zone on dial, so gas is ok

[Big_Roger]

Hi All that are puzzled by the mysteries of the gas in air con systems. And from the previous reply, this would seem to include some Halfords "mechanics" !!

A simple check on pressure in a system does not indicate all is well. It just means there is probably some gas in the system.

It requires sufficient refrigerant to make the system work properly, that is enough volume to cary the heat away from the evaporator.

The best equivalent I can think of is like when a camping gas cylinder is getting low, you can only get a low flame on the stove burner. This is because the small volume of liquid gas left doesn't have enough latent heat to keep the evaporation pressure of the liquid gas up to normal. It still works, but not at correct pressure.
You will get exactly the same pressure reading from a gas cylinder whether it is full or almost empty.  This is what your Halfords man has done.

Or, think of it as if you dont have enough water circulating in your engine cooling system. It will work to some extent, but not properly.

It's all about the volume of whatever medium available to transfer the heat.

The only way to be reasonably sure the system has enough gas is with a gauge set to read the high pressure coming from the output of the compressor, and the low pressure on the suction side of the compressor.
A certain range of readings on both gauges will show if the system has sufficient gas to work, but not how much gas (in weight) is in the system.

The only way to know that is to evac the gas from the system and weigh it, or on refill, with a known  amount in weight of refrigerant

If your air con seems to be nice and cool when you first switch it on, but after a while it is still cool, but not as cold as you think it should be, then it's a reasonable guess it's getting low on gas, and needs a trip to an air con specialist.

You need to remember that the compressor oil circulates with the refrigerant, and low refrigerant circulation also means low volume of oil circulating.

Roger

[philayl]

Hi, have just taken it to Kwikfit (I know ) It was 24 degrees at the face vent before, and 10.5 degrees after, so a result  

[dbug]

Hope its still cold in the morning!  Mine lost all its gas on the 10 mile journey home from Kwikfit.  Bunch of to**ers.

My mobile guy aims for 7ºC at vents - on the Estate (the Kwikfit cockup) he achieved 5.7ºC

[feeutfo]

in my experience 5c at the centre vent. Was like that for 5
Years, until the condenser got a hole in it. Just topping
Up the gas, is not even half the job.

[philayl]

Hope its still cold in the morning!  Mine lost all its gas on the 10 mile journey home from Kwikfit.  Bunch of to**ers.

My mobile guy aims for 7ºC at vents - on the Estate (the Kwikfit cockup) he achieved 5.7ºC

Still cold

[dbug]

Hope your luck holds