Anyone a guru on air conditioning? Golf MK4 GT TDi **SOLVED**
 

This is on a Golf GTTDI by the way...

A/C light comes on, get nothing.

Have it regassed - No leaks, told problem with compressor.

Give compressor clutch 12v, awesome cold aircon :DD:

After about 1 minute of enjoying my coldness, POOOFFFFFF - a shed load of refrigerant comes out the engine bay. Leave it for 5 minutes, try again, same thing..

I know there is a controller unit under the battery somewhere as the compressor was seeing 4.2V whether the engine was on/off or the aircon on/off

Any ideas? I've probably knackered something running it for a minute working :wall:

Sounds like you may have a blockage in the pipework to me or the pump is overpressuring the system but that could only be caused by a blockage really

possibly pressure switch (or sensor) failure. doesn't see pressure in the system so doesn't switch on the compressor and maybe didn't run the fans at full chat to keep the pressure down in the condensor so it vented out of the pressure relief valve.

at the very least you will need to have it recharged, and you should have some oil added now that you've vented a load.

as you've found out, overriding the circuit controls for some time is not a good idea, but can be useful for a moment to test compressor operation.

sounds like you should find a local expert to check it rather than a kwik fit recharge monkey

when you say re gassed did they who ever did it put it under a pressure test first

never done car stuff my self so cant belive (not saying there isnt) a pressure relief valve that dumps refrigerant into the atmosphere:wow:

thats the biggest no no in the aircon industry

I believe he did do a pressure test, I guess I'm just going to have to take it to someone to have a look.

Thanks for the replies though

:DD:

get someone with vagcom to check it for error codes

believe it :DD: i worked for the worlds largest automotive air conditioning compressor manufacturer for 12 years testing them, i should know

I'm going to have to pay for someone to come have a look I think..

From the various forums ive posted on, no one has a clue....

:(

you didn't find my post useful then :roll: have you checked it?

if you can give us more details on the car we might be able to help further using autodata with wiring diagrams, fault codes etc.

The climatronic system on that car is not so difficult to fault find, if you where near me i reckon i could give you the cause/fix in 30mins or so.

As Nick has stated, it has a trinary pressure switch, they leak through the switch into the wiring connector, actualy pressuring the multiplug onto the switch.

I could go on, but something for you to look at. by powering the compressor you have already told me the clutch is ok, and the compressor can generate high pressure, though by running it without fan control you have overloaded the system and the compressor blow off plug has blown out hence the refridgerant, big fan for knowingly releasing refridgerant to the atmosphere mate.

* big fine

why people no listen to people like us who actually know what we are talking about with this stuff? don't know why i bother with the ungrateful cunts sometimes :wall:

you know what you are talking about, but obviously the guy down the pub "knew something about something a while ago" and is a more trustworthy source of information than you are :cry:

i've got a leak on the mondeo that i'm pretty sure was when i dislodged one of the pipes when i changed the clutch on the compressor

a regas gave cold air but a few days later it was dead again so i'm getting someone who is an air con specialist to have a look at it for me before going to the pub to find someone who will fix it for 10p and a packet of pork scratchings :cry:

Thanks people, yes I did find your post helpful, ForeignRS .. and others..
Where is the pressure sensor switch and is there a way to bypass this as a test?
I think it may be underneath the wipers on the Golfs..

Just had a look on eBay and for the sake of £5-£10 it might be worth me just changing this..

Switch is £18.50 + VAT and can pick one up Monday.

Is it possible that this switch could cause 4V to the clutch to never change whether the car is on or off? Could there be a problem with the control module that sits under the battery?
Cheers
:smile:

Couldnt find the hi/low pressure switch, but I think this is it

http://shyde1.webspace.virginmedia.com/sensor.jpg

If thats it, how do you get to it to remove/test, I can barely get my fingers to it!

:?

that's it. test it at the other end of the wiring. autodata has wiring diagrams etc if you know anyone with it. otherwise tell us the year, engine code etc as i asked earlier and we might be able to help more. i won't be on here for the rest of the day probably though.

Hi there..
I'm having difficulty actually getting to the sensor. I can barely get my fingers to it.
Surely I dont need to remove the turbo inlet pipe?
Car is 52 plate ASZ engine (PD130)..
Thanks!

You have already proved that by-passing safety features on your a/c system results in over pressure of your system, resulting in the release of *refrigerant to atmosphere. Imagine if any part of your body was in close contact to refrigerant at high pressure.
You are not trained to work on this system, and your actions may result in injury to yourself or others.
PLEASE stop messing around with it, and take it to someone who is trained to work on it.
*there is no "d" in refrigerant or refrigeration.;-)

plus 1 on that

high pressure refrigerant shouldnt be messed with

it could leave you with very bad cold burns and its also an offence to knowingly let refrigerant leak to atmosphere as already mentioned
big fine and or prison

do you (the op) know there are refrigerants than can kill you with out you even knowing it :poke:

hence the long expensive courses we have to go on :tiff::cry:

just take it to somewhere that is aloud to work on these systems
not worth the risk mate

Yep, good point well made. Just trying to save a bit of money just like the next guy.

I'm in talks with a local aircon guy so will see what he comes back with.

r-e-f-r-i-g-e-r-a-t-i-o-n.

Got it. :grin:

Good man.:king:

No point in changing or testing the low/high pressure switch just yet.

Do you know how long the car has ran without a/c not working?
Has the filter dryer ever been changed?

If i was to look at it this is what i would do in order..

Recover gas left in system,
Fill with nitrogen and check for leaks (even tho it sounds like you dont have any)
Then change the dryer filter and vac down for a minimum of an hour,

Refill with refrigerant and check system... Once at this stage if its still not working i would the Go on to check wiring faults and pressure switches

Biggest failure i find to do with a/c is no one ever seems to change the dryer filter! This shoud be done at least every 2 years to keep the system from sludging

generally good advice, but he's already had it emptied, leak tested and refilled as stated at the beginning of the post, and it didn't work, although the compressor clutch does when powered directly. this already indicates a problem with the controlling circuit.

by the way, what would the system sludge up with? an r134a system with PAG oil unless messed around with in some way will remain clean internally for many years and that is based on seeing warranty returns from a wide variety of vehicles over the years.

the most likely problem that you might have with an old filter drier that has not been dried well enough by vacuum is moisture in the system that can freeze at the expansion valve and block the flow causing a high pressure cutout.

i just checked autodata and unfortunately that model does not have any self diagnosis features unlike later models, so it will be a case of using the wiring diagrams to find out what's wrong, or replacing components.

my advice would depend upon your capabilities. as already mentioned, you need to be careful with this stuff as you have already found out that running the compressor without the electrical safety circuits in place can lead to high pressures and refrigerant discharge which is unlikely to be toxic (as it should be R134a), but environmentally damaging (1300 times worse than CO2 :shocked:) and can seriously harm you through cold burns, loss of eyes etc.

for the sake of the cost of a pressure switch, which in my opinion is the most likely culprit (assuming you've checked all fuses), i would change that, but that first involves emptying the system (professionally recovering the refrigerant, not just venting it out). as i said previously, you will have lost some oil when the HPRV blew off, so it would be worth having that topped up with the correct oil before vaccing it out for at least an hour as previously advised and then recharging and retesting by someone who knows what they are looking at on the pressure gauges which can tell you a lot about the system.

hth :top:

EDIT: unless you have climate control, not manual, in which case fault codes are outputted but i can't copy and paste from autodata :wall: but 00792 is pressure switch and if you can read any others i can translate them for you

I dont belive the pressure switch is at fault,
If running the compressor for 1 min cause over pressure and vented then this tells me there is definatly a blockage in the system,

You can bridge the pressure switch to see if it cuts in, this will at least tell you if it is the switch tripping it out but it 100% has a blockage that needs to be sorted,

Vaccum it down for around 2 hours "should" remove any sludging,

I work on hgv's mainly so cant coment regarding hardware fitted to this particular car but ac is ac,

And as said above... Watch what your doing with this stuff, its not nice stuff,
Ive had a pipe on a eurorider coach blow before... 11000 kg's of gas exploding out the back of the coach as i was stood there!!!!!! Scary stuff!! Could of quite easily ended in disaster!

do the fans work when switch a/c on and stay on m8

Pressure switch can be changed without emptying the system, has built in self sealing valve for the purpose of ;)


11 tons of refrigeant ? WOW - im not suprised it blew lol ;-)

jesus.. that should of made the news!
must of been one very heavy coach!

sure it wasn't 11kg lol

haha sorry
11kg
11000 g lol

work in g's on the robin air machine lol not kg's :tiff:

Lol at 11 ton of refrigerant!
However, if you have to change the filter drier due to sludging, there is a much bigger issue.
The filter drier is in the system to absorb any moisture not removed from the system in the evacuation stage.
A torr gauge is a good tool in combating such an occurance.;-)

in theory. i wouldn't necessarily trust it, and he needs to have it recovered, oil added, vacced, leak checked and refilled anyway as he now has an unknown charge.

rollinz, you clearly know a bit about this, but 1 minute without any forced air cooling over an automotive condenser will definitely over pressurise until the HPRV blows off. believe me, i worked for the manufacturer of the compressor on his car, Sanden, for 12 years and have done various tests where we deliberately did things like this.

you are right that a blockage would also cause a similar effect to the high pressure side if the clutch was overridden, but a simple blockage would still give a balanced pressure sufficient to switch the compressor on in the first place which is not happening - hence most likely to be pressure switch failure.

maybe your robinar machine doesn't tell you that? ;-)

The robin air is what we use for filling thats all,

It gets a bit long winded trying to fill coach systems with a bottle and scales lol, so just program the machine and walk away and let it do its thing.


Ive only been doing A/C for about 4-5 years now so i dont know everything about it tbh!
May sound silly also but i have no idea how car compressors work! Most of my training and daily work is on sutrak & thermoking systems,

But essentialy a/c is a/c it still works in the same process cycle,

if you put a positive to the compressor you will get the compressor to run because you will be engaging the electromagnetic clutch

all this tells you is that the clutch is working and the last/first thing that stops working when there is a problem with the ac system is that the compressor doesn't get any power because it's designed to stop this sort of thing from happening

and i should know as i've just changed the clutch on mine as the wire inside had broken and it was the last thing he checked after checking all the other stuff and pressurising the system and all that stuff

Yes i know that,
The pressure switch is there to shut down the compressor if there is
1. Not enough gas and causes low pressure
2. A blockage causing high pressure

If the switch was just faulty and cutting the compressor out, then bypassing this by either bridging the switch or feedingthe coil on the clutch directly... Then the system will work..
But... In doing this his system over pressurised and blew off from a release valve?? (coach systems dont have this)

Now that all well and good but imo there has to be some sort of blockage to cause over pressure that quick..

This is why i am thinking the pressure switch isnt at fault... Its actually just doing it job...
Or whoever re-gassed his car has put way too much refrigerant in??

My thinking is that if it was just a faulty switch then it "should" of just worked fine when he bypassed this?

Or... Do these vag systems have an electically operated expansion valve that will open from the same control as the clutch?

Some erbaspratcher systems on coaches have these....

Please do bare in mind the 'pressure' device we are talking about is a sender, not a switch, shorting it out will not make any differance to it, its not 12v to ground like the basic older systems.

Running the compressor with no condenser fan for 1 minute will easily cause the pressure to rise sufficently that it would blow a pressure relief valve.
You seem to be fixated with the fact there is a blockage, when in reality it is far more likely that running the a/c system with no form of airflow over the heat exchanger has caused the refrigerant pressure to become so high that it has blown the relief valve.

After 1min??

As i said i dont work on cars,
Suppose a car been a smaller system it would freeze quicker..??

on the buses i used to drive we have a double ac system with 2 separate pumps and 2 separate systems, one for the front and one for back of the bus
or, in other cases, one for the lower deck and one for the upper deck

so it was quite easy to be travelling along in cold bliss while some of the punters were sweltering :cry:

so you've got to have a larger capacity for everything vs a car system which is only going to have something like 700g worth of refrigerant in it against the 11000g in the coach system which is possibly why you have come to that conclusion

yes, after 1 minute as several of us with experience of car systems have already said. if the high pressure gaseous refrigerant out of the compressor is not cooled in the condenser it will not condense (i.e. change from a gas to a liquid) and will therefore need a massive amount of volume within the condenser compared to what it would if it were liquid - this means high pressure.

what would be freezing? :?

back to school tomorrow for you i think :poke:

Today's lesson class is................................................ ..........Physics lol :)

All good fun.