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[old cruiser]

Had the air-con on for quite a while yesterday, but needed just a bit more power up some hills so pressed the ECO button and within seconds windows were misting up, so had to press Auto button again, any ideas why this is, is it something to do with residue from aircon in the vents and then not being cooled as it were? just hoping I've got no other issues here; the Pollen filter was changed a while back and no water collecting in scuttle area (drain holes clear)
Cheers Pete

[JamesV6CDX]

No first hand experience, but I'm willing to bet your pollen/cabin filter is completely blocked

[old cruiser]

As said i changed that not so long back, but going to check it again anway

[hotel21]

The aircon not only cools the air in/into the car but it dries it as well.  The interior shouldn't mist up right away but if it does, points to a real wetness inside the car.

Check the nearside carpet and matting beneath, then ensure the scuttle drain is clear and that the pollen filter is dry.  Fair chance thats where the fault is.

If alls clear then the inside must be getting damp from elsewhere.  I have used one of the cheap 9volt damp detectors you get in B&Q to check house walls for damp in car carpets to good success in the past.

[old cruiser]

Cheers Mate, I'll be checking these items tomorrow

[Kevin Wood]

The problem is that once the air con has been running, the evaporator will be damp with condensation. This is the damp it's taking out of the air and normally it drips down out of the bottom of the vehicle. When you turn the air con off, the evaporator warms up as it's not being cooled any more. The water starts to evaporate off it quite quickly giving you an instant steam-up.

You'll probably find that once the water has completely gone the screen will clear once more but air con is handy for keeping the screen clear without having the car heated to sauna levels.

Kevin

[Chopsdad]

Also check the boot.  In the "emergency" hideaway located behind the drivers side tail light you'll find a vent that often gets blocked with spare coats, blankets etc.  It wont make a huge difference but it may help.

[STMO123]

I.ve had two meegas and they just do this. It's no great pain to keep the aircon running.

[TheBoy]

Blocked scuttle drains (leading to wet pollen filters and carpets), and people filling the drivers side cubby hole in the boot with junk are the normal causes....

[Chopsdad]

Blocked scuttle drains (leading to wet pollen filters and carpets), and people filling the drivers side cubby hole in the boot with junk are the normal causes....

Inspired  

[JamesV6CDX]

I.ve had two meegas and they just do this. It's no great pain to keep the aircon running.

Agreed, very common, I've never had a meega that doesn't do it.

I just live with it, climate is always on for my comfort anyway

[Marks DTM Calib]

This is perfectly normal on cars with aircon......the condensator in the car will be drying the air as it passes and condensate will form on it (as per the inside of a window on a cold day), most of this drips out through the drains either side of the gearbox bell housing.

If you turn the aircon off, the air still passes over the wet condensator and hence steamy windows pretty much instantly!

So.....normal working!

[davlad22]

.....needed just a bit more power up some hills so pressed the ECO button

Not sure there should be an increase in power!?! That's a tale of old!  :-?

[Paul M]

.....needed just a bit more power up some hills so pressed the ECO button

Not sure there should be an increase in power!?! That's a tale of old!  :-?

Nope, the air-con compressor uses some of the power from the engine, so turning it off will free up a little more to overcome the load at the wheels. On most larger cars it's pretty negligable, but with a smaller engine it may be noticable.

Saying that, most cars should automatically disable the compressor on full throttle for this reason. Even my Impreza WRX STi used to do it, although I have serious doubts about whether the power loss from the compressor would even be noticable on a 300 BHP car at full chat!

[Marks DTM Calib]

The aircon compressor consumes about 1KW of energy....so just over 1Hp....it might be noticeable on a 1.0 Micra....but its not on a 2.2 Omega!