A/C not working... Evaporator temp @18C?

[Welly]

Good advice form Doggy there.

[puggy]

The switch ...


and the reason a/c wasn't working gas was leaking through it


looking from front of car its on lefthand side of a/c rad near the top

[puggy]

Dont remove it you will lose all the gas , its one of those buy one just incase
when you take it off it is leaking followed by a re-gas !!

[fattail95]

Thanks puggy. Was the leaking refrigerant causing the switch to read incorrectly then?

[gumby6371]

I'm watching this thread with interest as my AC hasn't worked since I've had the car.
I know precisely squat about AC systems, not even sure where all the bits are located under the bonnet.
If anyone fancies posting some nice engine bay pics with nice big idiot proof arrows and a simple check list then please do.
Also a guide to any checks using planet would be good.

Apologies for the hijack

[Welly]

I'm watching this thread with interest as my AC hasn't worked since I've had the car.
I know precisely squat about AC systems, not even sure where all the bits are located under the bonnet.
If anyone fancies posting some nice engine bay pics with nice big idiot proof arrows and a simple check list then please do.
Also a guide to any checks using planet would be good.

Apologies for the hijack

Basically:

Compressor (near alternator) turns low pressure refrigerant gas into a high pressure, high temp, liquid.....this goes through the Condenser (radiator-looking) up front and cools into a high pressure low(er) temp liquid it also has any moisture absorbed in the integral 'drier' (basically a desiccant bag)....then it reaches the Expansion Valve and Evaporator (like a heater matrix) the high press liquid passes through a tiny orifice (fnar fnar) into a large open space (the insides of the evaporator) [think: pressing on an aerosol can button] the liquid instantly vapourises back into a gas and absorbs heat in the process (it cools rapidly) the Evaporator goes very cold and air passing over it has its heat removed and thus provides cool air at the vents. The cooler low press gas then gets drawn back to the compressor and repeated....

It is important to remember that car a/c does not add cool air to the cabin but removes heat from.

[puggy]

Yes it is a pressure switch , if the pressure drops it shuts the system off .
There are several reasons for the a/c to not work , it took me £800 and dealing
with several so called profesional a/c technicians to sort mine out and it
was me that finally found the pressure switch was leaking .
You could start by finding a reputable a/c technician and having a re-gas because
they should start by emptying it and vacum testing it for leaks , you need to be there
so that if it is leaking you can tell them dont go any further . You then end up with
an empty system and they can put a dye in that shows the leaks , once you know
there are no leaks they can then re-gas if there are leaks change affected part while
system is empty then start again .

[Welly]

I have had a lot of experience with car a/c and have a range of T-Shirts available to mark various (expensive) mistakes, bullshitters, and other occasions. I too decided to take the bull by the gonads and find out the inner workings of such things for myself.

To that end I'm going to 'school' puggy (with utmost respect ) on his misinterpretation of the testing procedure; the system is firstly subjected to a nitrogen test at approx 300 PSi the operator will then observe the gauge watching for system leaks, obvious leaks will piss out and be accompanied by oil and dye leaks (seen via UV light and special spectacles) tiny leaks can be found by 'soaping' the joints and watching for bubbles.

Once the leaks are fixed ANOTHER test is done, then the system is held under Vacuum using a vac pump for at least 30 minutes this removes moisture in the pipework, any amount of moisture is bad for a/c and can cause blockages but under strong vacuum moisture boils-off and is recovered.

Once vac'd the new refrigerant, lubricating oil and dye is added and you're good to go.

[fattail95]

It's definately under pressure though, because when I depress the filling valve a load off refrigerant shoots out at very high pressure. Puggy do you remember exactly where the switch is?

Thanks

[puggy]

I bow to your superior knowledge Welly

[puggy]

With the engine running reach down get hold of the wires and wiggle
them to see if the compressor kicks in .

[fattail95]

Just given the wires a waggle, but nothing happened. I see the switch is hidden behind a plastic shroud? Is there an easy way to remove it?

And even though the system is still holding pressure, could the switch still be leaking refrigerant very slowly, meaning its a duff switch?

[puggy]

Thats what happened to mine , it lasted several weeks after re-gas till it
finally stopped . Stupidly it was the last thing i checked after several hundred
pound and like welly finding out we knew more about a/c than the technicians .
During the last few weeks of said leak my compressor sounded like it would rather
be somewhere else , the gas carries the lubricant for the compressor and it had
been running dry Remove the slam panel and front grill this will give you a little
more room to look at the condensor for leaks . Also while they are off you can check
the resistor things that control the fan cos if these are bolloxed it wont work either,
they all seemed to be linked up as a safety system .Look around the pipes where the
filler caps are these can leak too !

[rwb]

Well all this is sounding familiar

I was regassed in April, then 6 weeks later it wouldn't blow cold. Evaporator temperature getting down to 14 but no further.

Had it in again yesterday. They said that 450g out of 500g was in the system (and that ought to be enough for it to work), it passed the vacuum test, so we're back to seeing how it goes. There's now 25g of dye in it.

The only other thing that I can think of is the two valves. When the system is being tested they're plugged in and so no leak can be detected.

[fattail95]

Well all this is sounding familiar

I was regassed in April, then 6 weeks later it wouldn't blow cold. Evaporator temperature getting down to 14 but no further.

Had it in again yesterday. They said that 450g out of 500g was in the system (and that ought to be enough for it to work), it passed the vacuum test, so we're back to seeing how it goes. There's now 25g of dye in it.

The only other thing that I can think of is the two valves. When the system is being tested they're plugged in and so no leak can be detected.

Please let me know how it goes! Reeallllllyyyy dont want it to be the relay in the BSI D: