2 hours ago, froggy8 said:

just read that you have to have the AC on at all times,

You don't.

Use it if you need to be cooler than the coolest setting on your temperature dial, or if the car is getting misted up.  No need to use it any other time.

A small amount of refrigerant circulates all the time on modern clutchless A/C systems (like in your car) even when the system is switched off, so the argument about 'seals drying out if you don't use it' doesn't really apply.

3 minutes ago, Wino said:

You don't.

Use it if you need to be cooler than the coolest setting on your temperature dial, or if the car is getting misted up.  No need to use it any other time.

A small amount of refrigerant circulates all the time on modern clutchless A/C systems (like in your car) even when the system is switched off, so the argument about 'seals drying out if you don't use it' doesn't really apply.

thanks for that wino  

2 hours ago, froggy8 said:

ok thank you

 

as long as it is ok to have ac on when i have heat on too  

What does your owner's manual say?

This from the Daily Telegraph's Motoring Correspondent site. 

 

"Excellent explanation of how a/c works from Railroad in The backroom forum:

Air conditioning works by compressing, condensing and evaporating a refrigerant gas R134a. The gas boils at a very low temperature, -26 degrees Celsius. Under normal operation the compressor compresses the gas against an expansion valve (later in the system). The compressed gas becomes hot and at high pressure which then enters a condenser. Air passes through the condenser which allows some of the heat to be dissipated into the air which in turn causes the gas to condense into a high pressure liquid. The liquid the leaves the condenser and passes through a receiver dryer to allow and moisture which could damage components to be safely collected. The moisture free liquid then passes through a tiny nozzle (expansion valve), on the other side of which is a much bigger space. The liquid then becomes low pressure and subsequently the temperature falls considerably. The low pressure cold liquid passes into the evaporator which is inside the car. Heat from inside the car is drawn to the cold evaporator which then causes the low pressure liquid to evaporate into a low pressure gas, which in turn is drawn back to the compressor where the whole process starts over again.

If you don't run the system for long periods of time the gas will never turn to a liquid. The seals in the system can then dry out and deteriorate, causing the gas to be lost."

 

tom

There must be plenty on here that run cars through many years and seasons that had no A/C and yet they did not have steaming / fogging up interior glass and windscreens like 

you get with VW Group vehicles with all the choices of AC / Climatic Control.

Dry fresh car interiors with good ventilation and door / hatch seals.

51 minutes ago, e-Roottoot said:

There must be plenty on here that run cars through many years and seasons that had no A/C and yet they did not have steaming / fogging up interior glass and windscreens like 

you get with VW Group vehicles with all the choices of AC / Climatic Control.

Dry fresh car interiors with good ventilation and door / hatch seals.

Yes I well remember driving with open quarter-lights to keep the windows clear, and the rear window totally misted up (only after-market stick-on window heaters fitted)! And buying clip-on plastic window gizmos so you could drive with the side windows partly open to get a draught. 

If you want to go back to cars built more than half a century ago plus a decade or more then you might well be needing to do that.

But move to 3 decades or actually the 1970's so half a century back and things were improving and that was the past, as it is your stick on rear demister well in the past now.

 

Pity 20 years into a new century and European Car manufacturers have not got to grips with European weather and people travelling in cars and breathing.

Wind Deflectors still needed with many a car if you intend sitting in them when stationary and not getting soaked.

Edited 1 November, 20205 yr by e-Roottoot

A friend bought a new 911 Cabriolet last year and had persistent problems with the interior fogging up.  So much so that he eventually sold it back to the dealership, taking quite a financial hit in the process. 

I have manual aircon and only use it when I needed it, and yes the dehumidifier function works when the heater is set to warm. As a footnote my sister has a similar aged Ford Focus and she never turned the aircon off but she had to have hers regassed before mine.

9 hours ago, froggy8 said:

so i can set the temp knob to middle and i can still have AC on? i have always thought that to have AC on, i would have to turn the temp knob to coldest?

A very common misconception that AC is for cooling only.

 

If you’ve read all the above, you’ll get the idea that most folk leave AC on All The Time.

 

When everything is working properly you only have to tweak the temperature button occasionally and/or dial up the fan speed on really wet, steamy days or when carrying lots of people. Two little adjustments I make frequently and will be so ****ed off when I have to fumble my way through a touch screen to do so. AKA “progress”.

I find having the air con all the time is a bit of a vicous circle, it leaves the evaporator damp which leads to more condensation the next time you get in your car meaning you need to have the AC on again.

 

Since I started to leave it off it probably gets used a handful of times between the end of summer and the start of the next. Only if its a really really wet day or I have a few people in the car do I ever need it.

 

After about five months / five thousand miles the windscreen on my Karoq started fogging up all the time, and I was constantly having to use the quick clear function. I've since cleaned it with some decent glass cleaner and over the last three thousand miles it's been fine. Possibly some coating / product left on the glass from when it was built? 

It is usually the stuff the Dealership staff use getting a car ready to get it ready.

Then what comes from having the AC on.

Funnily non AC vehicles do not get the screen getting hazy inside the screen like A/C cars do.

I always thought the hazy film on the inside of the screen was from the vinyl on the dash.  

 

tom

You have that as well. Chemicals released from the plastics.  But then cars without AC also have plastic dashes and might not get the oily haze on the windscreen.  There were cars not that many years back without AC.