Talking of Aircon ...

Stick some uv dye in & see where it comes out.

Ah, cool, thanks. I'll run that by him and see if we can give it a go.

Cheers, T i m

Yep, infrequent use causes the seals to dry out. Winter's when aircon's most useful in the UK anyway.

Is this the seals in the joints or around the pump (or both)?

Yes, I think I have tried it for de-misting but not often.

Cheers, T i m

On 27/07/2013 18:48, Adrian wrote:> On Sat, 27 Jul 2013 18:27:55 +0100, T i m wrote: > >> the odd time we use the air con (mainly last year) >> Went to use it this year and nothing. > >> or is there something else known to offer this sort of symptom please? > > Yep, infrequent use causes the seals to dry out. Winter's when aircon's > most useful in the UK anyway. >

I hear that, and i unserstand the Theory.. But whenever I try A/C + Heat

• Windscreen blower my window mists up more...

What am I doing wrong?

Add to that it mists up if I have the AC on during the summer too!

first cause is blocked cabin filter, second is using recirculated air, third is blocked drain for the air con water.

Are you putting it onto recirculate? Don't.

The other thing to check is that the condensate drain's not blocked - with the aircon on, you should quickly gain a puddle of water under the car, as the air is dried and the water condenses out. If the drain's blocked, it's entirely possible that that water (with friends) is then being blown into the car.

I have the same issues. I think that after use, water condenses on the heat exchanger, and the next use releases that water. It clears after a while, but means using the A/C to demist is ineffective if used for multiple short journeys. I also dislike the the drier air created by using heat plus A/C; it always makes my eyes uncomfortable. (For that reason, I have disabled the automatic A/C function in my car.)

The other problem with winter use is that below a certain ambient threshold (4 C for most Fords) the A/C is disabled.

Chris

[...]

None of those problems have been evident in my car, but I still have the issue with misting on first use when having used the A/C earlier.

Chris

In theFocus I don't have any problem with mist on first use, the air con is never turned off. The Lexus however, does do a blast of mist first, sometimes enough to make you pull over till it clears.

I don't think it's quite as simple as purely ambient temp. IIRC humidity and refrigerant temperature are the key factors.

But where does the ECU get a humidity reading from?

Definitely mainstream Ford use the IAT sensor to turn off A/C via the ECU when it registers 4C or less.

Chris

There's a humidity sensor in any climate control setup.

The engine IAT sensor? So not ambient, then. The IAT is going to be a LOT warmer than ambient, even once the car's been running for only a minute or two.

I hadn't spotted any reference to climate control in this thread; not sure it would even be an option on an '04 Meriva.

Chris

This is to ensure that ice doesn't form on the matrix as this could distort the matrix causing damage.

1988 200SX Has a thermistor after the A/C matrix. When the outlet temp drops below 3°C it switches off the compressor. When the temp rises above 7°C it's switched back on. The "thermo amplifier" box with thermistor on a lead that does this trickery is about the the size of a disposable lighter and was £105 in 2000. Mine had suffered a slight calibration drift and was switching off at about 6°C, it was cool but wasn't really cold, so I re-calibrated the thermistor with 10p worth of resistors. No humidity detector needed.

ECU detects full engine power demand and switches the air con off. This is now very common on all cars with air con.

The Japanese version could have digital climate control. That had 2 extra sensors. A cabin temp sensor behind a grill on the centre console. A sun sensor so it could respond to rapid changes in solar load.

The aircon in my Meriva is on or off (although it's only off atm). ;-(

I'm looking forward to running some of the UV dye though it and suspect the condenser. The only time I got any reaction from the electronic sniffer was near the remains of a bug that was stuck on the front of the condenser. Do they have anything in them that could corrode whatever material the condenser is made of (ally?).

Cheers, T i m

I haven't specifically tested that, but at near zero temperatures the first thing I do with a misted screen is to press the magic button on the Mondeo which puts the blower on maximum, heat on maximum (if it's available), and switches on the A/Con. It probably over-rides the sensor to use the A/C, and it clears the screen in less than a minute.

Should be available on all cars.

What Ford have that should be on all cars is a quick clear heated front screen. That doesn't just de-mist but de-ices as well from cold.

The basic patent expired at least 7 years ago.

[...]

+1

Chris