C5 2.2 HDi Windscreen defrost

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wigelywoo
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C5 2.2 HDi Windscreen defrost

Post by wigelywoo »

I have 2.2 SX and I am wondering how long should it take to clear windscreen of frost in the mornings.Outside temp -6c to -4c.
when I press the switch for the windscreen the fan almost stops, It then increases in speed as the engine warms up. I usually have to clean the windscreen with a scraper.
Thanks in advance
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Clogzz
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Post by Clogzz »

Don’t know about the C5, but the Xantia Mk II with air conditioning automatically turns on the aircon when you direct the air at the windsceen.
When the outside temperature is less than about +5ºC, the aircon won’t start to prevent the compressor from frosting up.
After it’s warmed up under the bonnet from running the engine, the aircon can start and demist the inside of the screen.
The interior fan probably slows down when directing warm air from the heater at the frosted windscreen to protect the glass while it’s very cold.
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Post by bxbodger »

The interior fan probably slows down when directing warm air from the heater at the frosted windscreen to protect the glass while it’s very cold.
I think its more likely theres something wrong with it!!

I'd have thought that the blower fan should operate at full speed to demist the screen whatever the outside temperature-after all, you only need to demist the screen in cold weather....... switch the aircon off and see if that makes a difference.
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fastandfurryous
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Post by fastandfurryous »

Clogzz wrote:When the outside temperature is less than about +5ºC, the aircon won’t start to prevent the compressor from frosting up.
After it’s warmed up under the bonnet from running the engine, the aircon can start
The temperature sensor for this is in the airflow just after the aircon evaporator, so underbonnet temperatures can have nothing to do with whether the Aircon will run or not (other than overheating of course). If the outside air is below +5, then the aircon simply will not run at all.

The climate control in most later aircon pugs/citroens is clever enough to measure coolant temperature, and when it's still cold, the fan (in AUTO) won't run very fast if you have heating selected, as of course you won't get any hot air out!

On top of that, the HDI engine is very efficient, and hence it's heat output is very low at idle, so it will take ages for the heater matrix to warm up, for the system to then recognise that it has heat available, and thus turn the fan speed up.

Either: let the engine idle for longer, such that there is heat available, and the system turns up the fan speed.

Or: manually set the fan speed. The downside of this is that the air coming out of the vents will be cooler than you'd like.

The essence of the problem is that you need heat to defrost the windscreen, and the climate control knows that. The engine would need to be idling for a good 5 minutes or so before there is any decent amount of heat available to defrost the screen.

I think the system is working just fine!
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Post by PowerLee »

The climate control / aircon fitted to my 2003 Pug 206 runs at outside temps below +5 C & straight away from a cold engine start.

You can hear the A/C clutch engage & hear the engine cooling fan running.

When I press my windscreen de-mist button the heater gets louder & rapidly clears the inside of the windscreen.
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fastandfurryous
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Post by fastandfurryous »

PowerLee wrote:When I press my windscreen de-mist button the heater gets louder & rapidly clears the inside of the windscreen.
No doubt, as to clear mist simply requires dry air to flow across the screen. The OP is referring to defrosting the outside of the screen, which needs heat. :wink:
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Re: C5 2.2 HDi Windscreen defrost

Post by Homer »

wigelywoo wrote:I have 2.2 SX and I am wondering how long should it take to clear windscreen of frost in the mornings.Outside temp -6c to -4c.
I would guess at about half an hour, if at all.

There's nothing faster at clearing ice than a scraper (and a good pair of gloves).

Heated front windscreen comes close but AFAIK Citroen don't do them.
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