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98 S70 -- Defrost, AC on?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

mar601
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98 S70 -- Defrost, AC on?

Post by mar601 » Sat Nov 23, 2019 11:00 am

It's winter so time for the heater and I've noticed something I haven't seen before. When the fan is on (auto or manual) and the temp control is 72, I can turn the blow position switch to every position and the heater functions normally but when I turn it to the defrost setting (12 o'clock) the AC (green light) comes on. Only on this defrost setting does the AC come on. (Not sure if the actual AC compressor turns on but the green light does). -- thanks for any help



mar601
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Re: 98 S70 -- Defrost, AC on?

Post by mar601 » Sat Nov 23, 2019 11:01 am

and pretty sure it's never done this as I've always used the defrost setting to melt ice.



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amblerman
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Re: 98 S70 -- Defrost, AC on?

Post by amblerman » Sat Nov 23, 2019 11:15 am

That is normal. The AC helps dry out the air and helps get rid of some of the fogging on the windows better than just heat alone.

This is especially useful when you are wet from rain or snow and you get in your car. Then the moisture you brought in with you evaporates and wants to settle on the cold windshield thus fogging it up. The AC combined with defrost helps clear it quicker as the air is drier due to the AC being on. Especially if you use the recirculating feature.

If you don't want the AC to come one, turns your climate mode dial one click away from the defrost setting. It will still (mostly) be on defrost but won't trigger the AC to pop on.



mar601
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Re: 98 S70 -- Defrost, AC on?

Post by mar601 » Sat Nov 23, 2019 12:05 pm

Did not know that ! Thank you -- so which way should I turn 1 click away? left or right or does it matter? I never use the AC at all in the summer -- have always been paranoid about it clicking on in the first place.



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amblerman
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Re: 98 S70 -- Defrost, AC on?

Post by amblerman » Sat Nov 23, 2019 3:02 pm

Having the AC on will definitely help if there is a lot of moisture in the air.
ie: fall with rain, warmish winter with slushy snow that gets in your car, snow on you that melts while in car, etc. ALl of those things will add moisture into the interior of your car and contribute to fogging up your windshield.

However, if it's the dead of winter where the air is dry anyway I don't think the AC contributes anything so long as you aren't adding moisture to the inside of your car.

Why are you paranoid about your AC even in summer? Is there an issue with it? If it works properly, it's meant to be used. :-)
-A



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