Air Con

[allanmc]

My car 2000 Xantia 2Ltr HDI 110 bhp I have a question about the AC System some people say leave it switched on all the time others say just switch it on when you need it what do you think.
Thanks

[MJM]

Switch it on when you need it. Mine doesn't get used for months at a time, not even the odd 10 minutes or so and is still cold at 11 years old.

[citroenxm]

The reccomended procedure to keep the system in working order is to use it once for 10 mins a week AT LEAST!

This keeps the system all running and seals lubricated.. You WILL find though being a 2000 model that everytime you select Windscreen Demist on the heater slider it Will automatically switch the air con on Regards to the dash switch being on or off... this is to speed up demisting as REMEBER: Air con is also a de-humidifer or if you like an "Air Dryer"

This feature was only added to 2000 late W, X and Y plate cars..

Paul

[allanmc]

Thanks for your reply Ill give that a try.

[John Plum]

I wonder, apart form rifing in someone elses xantia with ac, how could I get an idea of it's present performance.

Example: mine cools down to 17 - 18 C on the cabin temp meter, I feeel the cool, biut in the sun find myself thinking i wish it worked better, and open the windows. On the motorway, I shut them and it's just OK. I wanted COOL.

Does 17 C sound right? Is there some tweak or test for performance?

[addo]

The high side and low side pressures need to be read with correct gauges.

I'd suggest (unless you have 100% confidence in the mechanic's integrity) having this test done as a freestanding procedure - stops dishonesty.

[xantia_v6]

If you can measure the temperature of the air coming out of the face vents with the slider at minimum temperature, this should after a couple of minutes drop to less than 5 degrees. On mine, on a hot day it can get as low as -11. If the distributed air is cold (on a hot day) then the refridgeration system is OK.

If the distributed air is fairly cold on a warm day, but not very cold (above 5 degrees) on a hot day, there is a very good chance that your system needs more R134. I think the system gets into a state where nearly all the R134 is pumped into the HP side of the system, but the pressure there is still too low for it to condense properly on a hot day, but the pressure on the low side is too low for the pump to scavenge much gas, and the systme just limps along.

My late Mk1 system (which may have different software to yours) has an odd behaviour in that it works really well when the outside temperature is over 30 degrees, but when the outside temperature is only in the low 20s, even if the indside of the car is hot (due to solar gain), it won't cool the car to the desired temperature, you have to move the slider down a few dergrees. This is obviously a software quirk.

BTW, I run my A/C all the time when the outside temperature is over 7 degrees. When it is not doing much cooling, it is not using much power.

[DickieG]

On mine, on a hot day it can get as low as -11.

Are you sure about that, as such a low temperature will cause the system to freeze up, IIRC the lowest temperature out of the vents should be around 5 degrees.

[cachaciero]

On mine, on a hot day it can get as low as -11.

Are you sure about that, as such a low temperature will cause the system to freeze up, IIRC the lowest temperature out of the vents should be around 5 degrees.

That sounds right to me, as has been said the system is also a de-humidifier water condenses out of the incoming cabin air on the evaporator, hence the water dripping out underneath. If the evap gets down to 0 degrees ice will start to form in the matrix and eventually choke up completely, you will get very cold air for a while and then none . With an evap at close to 0 degree 5 degrees at the outlet sounds about right.

And yes, as has already been said, the system should be run regularly specifically to keep the compressor seals in good shape.

cachaciero

[xantia_v6]

On mine, on a hot day it can get as low as -11.

Are you sure about that, as such a low temperature will cause the system to freeze up, IIRC the lowest temperature out of the vents should be around 5 degrees.

It takes a surprisingly long time for the evaporator to get choked with ice, even in a humid climate, so these computer controlled systems can deliberately take the evaporator temperature very low for a few minutes for maximal cooling, then let them recover to just above freezing to thaw out.

[DickieG]

On mine, on a hot day it can get as low as -11.

Are you sure about that, as such a low temperature
will cause the system to freeze up, IIRC the lowest temperature out of the vents should be around 5 degrees.

It takes a surprisingly long time for the evaporator to get choked with ice, even in a humid climate, so these computer controlled systems can deliberately take the evaporator temperature very low for a few minutes for maximal cooling, then let them recover to just above freezing to thaw out.

I've never heard that IIRC correctly the original Citroen W/S manual gives the lowest output temperature as 5 degrees and makes no mention of briefly going to such low temperatures on startup, no Xantia of mine ever has and I'm very fussy when it comes to the efficiency of how well A/C works on my car's, so should I suspect the system on one of mine isn't working well I check the output temperature with a thermometer probe.

The A/C fitted to BMW 5 Series E39 onwards is very effective but even those don't peoduce air at minus 11 degrees

[Kowalski]

On mine, on a hot day it can get as low as -11.

Are you sure about that, as such a low temperature will cause the system to freeze up, IIRC the lowest temperature out of the vents should be around 5 degrees.

It takes a surprisingly long time for the evaporator to get choked with ice, even in a humid climate, so these computer controlled systems can deliberately take the evaporator temperature very low for a few minutes for maximal cooling, then let them recover to just above freezing to thaw out.

Isn't the TX valve mechanical and thermostatic?

[cachaciero]

Isn't the TX valve mechanical and thermostatic?

Yes if it has a TX valve and not some other kind of throttling device.
The valve controls the superheat of the refrigerant i.e the difference between the actual gas temperature and the gas temperature expressed as pressure. It's usually adjustable within a narrow range.

cachaciero