How to disable V90 air conditioning in winter?

[martin calva]

My Question:
What fuse (or relay) can I pull out that will disable the air conditioning, yet leave the rest of the heating and ventilation system in operation?

Background:
Evidently, with the V90, if you direct the air to the windscreen, irrespective of the temperature your have set the control to, the air conditioning comes into operation and the little blue light behind the air conditioning button lights up. So far as I can see, there is no combination of controls that allow you to blow hot air on the windscreen without having the air conditioning coming into operation.

In winter I have no need for air conditioning but I'd like to be able to blow hot air onto the widscreen - for example when someone with a wet coat has got into the car - without the A/C operating.

(I have looked at the page in the V90 electric manual but I cannot make any sense of the diagrams.)

[CoopsSA]

Can't see why you wouldn't want the air conditioning on - it's draws the moisture from the car thereby assisting the heating?

My air conditioning is on all the time, it is never switched off.

[martin calva]

Originally Posted by CoopsSA

Can't see why you wouldn't want the air conditioning on - it's draws the moisture from the car thereby assisting the heating?

My air conditioning is on all the time, it is never switched off.

Having the air conditioning on is not cost free. The air conditioning increases fuel consumption - and no doubt wear and tear on the compressor.

I'm not sure that cooling the air (admittedly dehumidifying it) then passing it through a heater will then result in air that is more effective in clearing the windscreen in situations where there is copious emission of water vapour from inside the car (from the passengers' wet coats).

I can see that, if you are blowing on the windscreen and not drawing in external air, it would make sense to use the A/C to remove the moisture from inside the car but that's not what I do.

In another Volvo, without A/C, having the fan on full and the temperature at max very quickly clears a fogged windscreen, even with wet passengers on board. That's all I want to do in the V90 but without the thought that I'm paying to have the A/C running against my wishes.

[Laird Scooby]

The reason the A/C automatically switches on when you set the controls to demist the screen is so it blows conditioned (dry) air onto the scren to demist it quicker.

Nothing special about the V90, every car i've ever known has done this.

In other words, it's common practice, you could potentially over-ride it by hitting the "Economy" button if you have one or perhaps the A/C button to switch it off manually but it is good practce to run the A/C at least once a month for at least 20 minutes to prevent the seals drying out and leaking, which lets the gas escape.

That will cost more to have fixed than any (very slight) decrease in economy you may suffer from the A/C working when you don't think it should.

[CoopsSA]

Originally Posted by martin calva

Having the air conditioning on is not cost free. The air conditioning increases fuel consumption - and no doubt wear and tear on the compressor.

I don't think you'll even notice having the A/C on or off, any increase or decrease in fuel consumption is negligible.

Likewise the compressor, there will barely be any wear and tear on it. They are designed to remain on. On a previous Skoda, I ran the car for 4 years and 124k miles with the A/C always on with no effect on the compressor.

[Rversteeg]

With an almost empty AC system it could make sense to switch it off, otherwise it will keep on switching on and off very quickly.
On my 940 I switched it off by pulling the low pressure sensor connector on the drying unit. I guess it will not be much different on a 960.

[Laird Scooby]

Originally Posted by martin calva

Having the air conditioning on is not cost free. The air conditioning increases fuel consumption - and no doubt wear and tear on the compressor.

I'm not sure that cooling the air (admittedly dehumidifying it) then passing it through a heater will then result in air that is more effective in clearing the windscreen in situations where there is copious emission of water vapour from inside the car (from the passengers' wet coats).

I can see that, if you are blowing on the windscreen and not drawing in external air, it would make sense to use the A/C to remove the moisture from inside the car but that's not what I do.

In another Volvo, without A/C, having the fan on full and the temperature at max very quickly clears a fogged windscreen, even with wet passengers on board. That's all I want to do in the V90 but without the thought that I'm paying to have the A/C running against my wishes.

When fresh air is drawn in from the oustide and passed over the A/C evaporator, it causes the moisture content of that air to condense on the evaporator - this air is then heated by the heater (without its moisture content) to demist the screen.
The condensate is drained off through the channels built into the system for this purose and exits below the car - that's why you will often see a puccle form below and A/C equipped car.

If you set the HVAC controls to Recirculate, it will pull all the moisture it can from you, from the seats, from your passengers and distriute that moisture on the inside of the galss, thereby misting it all up.

If you're really that bothered about the minimal cost of the extra fuel, either stop picking up soggy passeners or sell it and buy a non-A/C equipped car. By the same token, if a compressor is not used/used minimally, it can lead to premature failure for other reasons - the cost of a new compressor plus fitting, plus oil plus new gas plus testing and all other labour costs involved far outweigh the cost of running the A/C in the first place.

Also, it's cheaper to run the A/C in hot weather than driving along with the windows open!

[Clan]

Originally Posted by CoopsSA

I don't think you'll even notice having the A/C on or off, any increase or decrease in fuel consumption is negligible.

Likewise the compressor, there will barely be any wear and tear on it. They are designed to remain on. On a previous Skoda, I ran the car for 4 years and 124k miles with the A/C always on with no effect on the compressor.

Indeed the difference will be negligible considering the shocking fuel consumption of these cars anyway compared to the newer volvos which use half the amount of fuel ...

[Tyron760]

Originally Posted by Rversteeg

On my 940 I switched it off by pulling the low pressure sensor connector on the drying unit. I guess it will not be much different on a 960.

Thats the way to do it.

[Baxlin]

Partly tongue in cheek, but partly not.....

I would have thought that if you are that worried about the effect of th a/c on fuel consumption, you would also worry about carrying around all the unused a/c equipment throughout the winter....

Just put an extra lb pressure in the tyres, drive a few mph slower, and wear softer shoes so you don’t have such a heavy right foot when accelerating. These should more than make up for the a/c being on.

And enjoy the benefit of having air conditioning in your car.

But then I’m in the "a/c on all the time" camp. Oh, except when I have the top down. And the latter really does affect mpg!