Air con: it's not working...but it works!

[Thom]

When I got the leak repaired the chap told me a thing called the "détendeur" is out of order.
Sorry, even in french I have no idea what is

I was told this device is supposed to regulate the gas pressure in the air con system; the problem is it is located behind the engine and is a bit** to get to.

Meanwhile, the guy told me I could drive with the air con on, but not too fast, namely below 4000rpm.
This is fine for B-road use, but I neither see myself cooking in the car when I visit Germany next summer nor being thrashed past by the inevitable 5-series on the Autobahn because of having to behave below 4000rpm...

Any thoughts? Have I been told boll**** about this so-called "détendeur" or can I drive in a peaceful mind?

Thank you for your advices

[mondeoman]

Hmmm, interesting..... Not sure what the translation is, but there aren't that many components on a fridge system that can go that wrong.. Mostly they are gas temp/pressure sensors. This could be the main regulator (unlikely tho - wrong name?!)which measures the "superheat" coming from the evaporator (main chiller matrix) and if that failed you could get liquid refrigerant into the compressor - BANG. Other one could be the condenser fan controller (measures liquid temp from the condensor) if that went wrong, ummm, damn inefficient and possibly burst the condensor matrix with over-pressure.

How any of this relates to engine speed I've got no idea - the compressor normally has an electro-magnetic clutch controlled by the air-temp setting..which in turn looks after the expansion valve... Its not a complicated bit of kit.

Was the chap who fixed it an air-con specialist??

[Thom]

quote:
components on a fridge

That's a jem; until I read this I thought my car was just a dishwasher...just joking

Seriously, the chap knows very well about air-cons; he used to work on Bus air-cons and now has his own air-con company.

I don't think the "main regulator" as you call it has passed away: before the leak appeared the air-con worked perfectly for several months, whatever the revs.
Had it been wrong, it would have gone bang as you just pointed out, which it has not.

As far as the condenser fan controller is concerned, very cold air is blown out the vents, so it might not be out of order.

But now that makes me think of something else: had the leak acted as a "auxiliary security pressure valve"? I mean, do you think it could have gone bang if there had been no leak at all?

The link with engine speed is that the higher the engine revs, the more cold is produced, because (?) of the magnetic clutch.

Thank you for your reply; I will work out your thoughts...

>> Edited by Thom on Thursday 27th June 13:27

[JSG]

Thom,

I'm far from being an expert on air con or French language but I'd assume détendeur is from détendre meaning to release / relax and therefore he is refering to a pressure release valve in the system. As you point out this could be what caused the leak if it was faulty and allowed too much pressure to build up.

[mondeoman]

quote:
Thom,

I'm far from being an expert on air con or French language but I'd assume détendeur is from détendre meaning to release / relax and therefore he is refering to a pressure release valve in the system.

That would explain the reference to maintaining a slower engine speed - as the speed increases, the output pressure from the compressor increases, which could take you beyond the limits of the faulty PRV and either it operates at a lower pressure and you lose refrigerant or the weakest link is found and a leak develops elsewhere in the system.

So, that being the case, you are limited to 4000 rpm or you pay to have it fixed...... what price comfort???

[Thom]

quote:So, that being the case, you are limited to 4000 rpm or you pay to have it fixed...... what price comfort???

Yes, anyway I get hot each time I rev it beyond 4000tpm
I will make do with it

[v8guinness]

Some A/C systmes de-clutch at higher engine speeds (side benefit allowing more power to road wheels) mainly to preserve compressor, which needs to be geared to work well at idle, but shouldn't be over revved...

So just a thought, but he doesn't mean clutch???

[Fatboy]

If you're doing over 4000 in top gear surely you can just switch off the air-con and open a window?

Could save you a packet...