I have the car booked in for the air conditioning to be regassed, as the car is no longer cooling but would this also affect the lack of demisting of the windscreen today in the rain? I was wondering if demisting is solely the function of the AC compressor so maybe that has failed?
Misty windscreen despite A/C.
- Thread starter Ltnman
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Using AC can hugely decrease the time that it takes a windscreen to demist.
Some cars have a demist button - this will usually adjust the vent positions, set the fan and heat to maximum, whilst running the AC.
The warm air can hold more moisture, its then passed through the AC coils, cooling and drying the air, allowing the condensate to drip out of the car.
So, if your car does have a 'magic' demist button, without AC, the demist performance will be reduced.
Some cars have a demist button - this will usually adjust the vent positions, set the fan and heat to maximum, whilst running the AC.
The warm air can hold more moisture, its then passed through the AC coils, cooling and drying the air, allowing the condensate to drip out of the car.
So, if your car does have a 'magic' demist button, without AC, the demist performance will be reduced.
The A/C isn't working.
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Do you 'clear' the windscreen by rubbing your hands on the screen as well? If so then degrease to screen by cleaning with a good glass cleaner. That will speed up demist time.
The question is based around does the gas, the compressor or both contribute to the demisting of the windscreen?
I don’t want to pay for regassing if the compressor, which is covered by an exstended warranty is faulty. As part of a compressor repair the gas would then be covered by the warranty.
I don’t want to pay for regassing if the compressor, which is covered by an exstended warranty is faulty. As part of a compressor repair the gas would then be covered by the warranty.
Yes.
The compressor compresses the gas. It then passes through the condenser (the radiator in front f the car's actual radiator), where it turns into a liquid. It then goes round to the expansion valve at the entry to the evaporator, where it turns back into a gas. Just as an aerosol gets cold as you use it (because the liquid propellant inside is expanding into a gas, taking heat from its surroundings to do so), the refrigerant in the aircon system expands into a gas in the evaporator, dropping the temperature of the evaporator as it does so. This takes heat out of the incoming air, passing over the evaporator fins. The gas then carries on back to the compressor, where the cycle begins again.
So the compressor is just one part of the system, as is the refrigerant gas. All the parts need to be there and working, for the aircon system to work. (and yes, it does massively speed up demisting, for the reasons explained by RandomGrinch). Compressors rarely fail in this country. If they fail, they usually make a knocking noise when they're running. All aircon systems have a safety pressure switch that cuts the power to the compressor if there's insufficient gas pressure, because the compressor could be damaged in that situation. Don't assume, therefore, that just because the compressor isn't turning, it's broken.
Lastly, if you have a pollen filter (sometimes called a cabin filter) that hasn't been changed for a while, that can make demising a bit harder.
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