Hi all its the pest again, I have just had the air con refilled due to the fact i changed the radiator some two months ago, the mobile air con gent called, did all the checks, removed all the moisture ect, filled the system great no problem. Started the Rav. inserted his thermometer in my air vent great he said, working fine, now what i cant understand ( and what the gent says is normal) why is it that the compressor runs for a short time stops for a minute starts again stops, and so on and so on, please gents put me out of my misery. regards John

It is perfectly normal. The pump is simply maintaining a pre-determined pressure and how long it is working will depend on how hard the aircon is being worked.

The compressor builds up pressure in the pressurised side of the system and then it is forced through an orifice so small that emerges from the other side as a low pressure gas. It works on a similar principle to a fridge in that opposite to compressing a gas the temperature rises (like in an engine or even a bike pump) if you depressurise it the temperature will fall. This cold gas is then fed through a radiator which does two things. Air diverted from the heater over it will be cooled for use in cabin air temperature control. Secondly, moisture in the incoming air condenses on the outside of the radiator and this has the effect of dehumidifying the air - great for demisting windows and avoiding drowsiness. The residue of the moisture is piped outside which is why you can see water dripping on a warm day. After leaving the heater the gas is fed through a condenser which converts it back to a low pressure fluid and back to the pump where the process starts again. This is a simplified account but I'm sure you would find something in wikpedia or some similar site.

Hope this helps.

[quote name='anchorman' post='694191' date='Nov 18 2007, 01:20 PM']and avoiding drowsiness.[/quote]

Important at our age!

[quote name='anchorman' post='694191' date='Nov 18 2007, 01:20 PM']It is perfectly normal. The pump is simply maintaining a pre-determined pressure and how long it is working will depend on how hard the aircon is being worked.

The compressor builds up pressure in the pressurised side of the system and then it is forced through an orifice so small that emerges from the other side as a low pressure gas. It works on a similar principle to a fridge in that opposite to compressing a gas the temperature rises (like in an engine or even a bike pump) if you depressurise it the temperature will fall. This cold gas is then fed through a radiator which does two things. Air diverted from the heater over it will be cooled for use in cabin air temperature control. Secondly, moisture in the incoming air condenses on the outside of the radiator and this has the effect of dehumidifying the air - great for demisting windows and avoiding drowsiness. The residue of the moisture is piped outside which is why you can see water dripping on a warm day. After leaving the heater the gas is fed through a condenser which converts it back to a low pressure fluid and back to the pump where the process starts again. This is a simplified account but I'm sure you would find something in wikpedia or some similar site.

Hope this helps. Thanks anchorman, you have put my mind at rest, one of the reasons that concerned me, the air con on the vauxhall vectra (family car )
the pump never stops ( when it is switched on) thanks very much for the reply regards John[/quote]

[quote name='Johnmerc' post='694273' date='Nov 18 2007, 06:50 PM'][quote name='anchorman' post='694191' date='Nov 18 2007, 01:20 PM']It is perfectly normal. The pump is simply maintaining a pre-determined pressure and how long it is working will depend on how hard the aircon is being worked.

The compressor builds up pressure in the pressurised side of the system and then it is forced through an orifice so small that emerges from the other side as a low pressure gas. It works on a similar principle to a fridge in that opposite to compressing a gas the temperature rises (like in an engine or even a bike pump) if you depressurise it the temperature will fall. This cold gas is then fed through a radiator which does two things. Air diverted from the heater over it will be cooled for use in cabin air temperature control. Secondly, moisture in the incoming air condenses on the outside of the radiator and this has the effect of dehumidifying the air - great for demisting windows and avoiding drowsiness. The residue of the moisture is piped outside which is why you can see water dripping on a warm day. After leaving the heater the gas is fed through a condenser which converts it back to a low pressure fluid and back to the pump where the process starts again. This is a simplified account but I'm sure you would find something in wikpedia or some similar site.

Hope this helps. Thanks anchorman, you have put my mind at rest, one of the reasons that concerned me, the air con on the vauxhall vectra (family car )
the pump never stops ( when it is switched on) thanks very much for the reply regards John[/quote]
[/quote]

John

I think it must have stopped because you would have to find some other way of regulating pressure. However, on some pumps the pully rotates continuously and it only engages the drive shaft intermittently. These pulleys especially on petrol engines help to reduce the ***** you sometimes feel when the aircon cuts in as they engage progressively.

Cheers

[quote name='anchorman' post='694284' date='Nov 18 2007, 05:21 PM'][quote name='Johnmerc' post='694273' date='Nov 18 2007, 06:50 PM'][quote name='anchorman' post='694191' date='Nov 18 2007, 01:20 PM']It is perfectly normal. The pump is simply maintaining a pre-determined pressure and how long it is working will depend on how hard the aircon is being worked.

The compressor builds up pressure in the pressurised side of the system and then it is forced through an orifice so small that emerges from the other side as a low pressure gas. It works on a similar principle to a fridge in that opposite to compressing a gas the temperature rises (like in an engine or even a bike pump) if you depressurise it the temperature will fall. This cold gas is then fed through a radiator which does two things. Air diverted from the heater over it will be cooled for use in cabin air temperature control. Secondly, moisture in the incoming air condenses on the outside of the radiator and this has the effect of dehumidifying the air - great for demisting windows and avoiding drowsiness. The residue of the moisture is piped outside which is why you can see water dripping on a warm day. After leaving the heater the gas is fed through a condenser which converts it back to a low pressure fluid and back to the pump where the process starts again. This is a simplified account but I'm sure you would find something in wikpedia or some similar site.

Hope this helps. Thanks anchorman, you have put my mind at rest, one of the reasons that concerned me, the air con on the vauxhall vectra (family car )
the pump never stops ( when it is switched on) thanks very much for the reply regards John[/quote]
[/quote]

John

I think it must have stopped because you would have to find some other way of regulating pressure. However, on some pumps the pully rotates continuously and it only engages the drive shaft intermittently. These pulleys especially on petrol engines help to reduce the ***** you sometimes feel when the aircon cuts in as they engage progressively.

Cheers
[/quote] Thanks once more for your time and trouble regards John

[quote name='anchorman' post='694191' date='Nov 18 2007, 01:20 PM']and avoiding dozyness.[/quote]

Best get the wife to put the A/C on all the time then

[quote name='wack' post='695345' date='Nov 20 2007, 07:42 PM'][quote name='anchorman' post='694191' date='Nov 18 2007, 01:20 PM']and avoiding dozyness.[/quote]

Best get the wife to put the A/C on all the time then
[/quote]


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