aircon just stopped

[finallyrangie]

Hello people

I'm hoping one of you learned individuals will be able to give me either a simple answer or something else to but I have a horrible feeling I will have to spend some money.

Finally got some gas into the air conditioning system a couple of weeks ago and everything was good the air was cold and the wife was happy.

Yesterday afternoon we jumped in the car and by the end of the street it was obvious we had no aircon so the investigation began this morning .

Fuses are all good, relays have been replaced one by one and nothing changed. The compressor is running, so I assume the gas is still in there, and the high pressure side is getting hot, so it's compressing something, but still no cold air in the cabin.

I know it could be a leak but it went from 2 weeks of fully cold to nothing, literally overnight so I am wondering if there might be another problem.

Any suggestions greatly appreciated, I have no more ideas and auto electricians are expensive!

[Eevo]

The compressor is running, so I assume the gas is still in there,

i dont think you can make that assumption

[finallyrangie]

Oh dear

That statement was based on my being told years ago that there is a pressure switch in the system I know it didn't run when it was empty.

How likely is it to have lost the gas overnight

The refill receipt mentions a dye in the gas anyone know what colour I will be looking for?

[Eevo]

Oh dear

That statement was based on my being told years ago that there is a pressure switch in the system I know it didn't run when it was empty.

How likely is it to have lost the gas overnight

The refill receipt mentions a dye in the gas anyone know what colour I will be looking for?

my wrx didnt have a pressure switch.
might depend on the car.

if there is a leak, all the gas can go under an hour

its a UV dye.

[Blknight.aus]

first check the compressor is engaging and disengaging. engine running turn the AC on and the clutch should pull in turn it off and it should disengage.

if that does what its supposed to you've eliminated most of the controls and electrical functionality.

with the compressor running touch the hoses on the compressor, the fat one should get cooler as soon as the compressor engages and the skinny one should start to get hot. If that works you still have some gas but you may only have just enough to operate the low pressure switch and not enough to actually make the AC function.

IF you dont get any action on the temperature change on the pipes find and disconnect the hi/low pressure cutout switch on the system if that then drops the compressor out you might have a dead LP switch thats not indicating low pressure OR your valves in the compressor have given up.

From there if all that is working and the discharge pipe on the compressor gets warm briefly then its time to start looking for a restriction in the system, If the receiver drier is blocking up then you'll have heat on the pipe from the compressors to the receiver drier and the discharge line from the receiver drier will be cool to cold. if you have a sight glass in it (and you should) have a look at it see what thats doing.

if youve got clean liquid coming across that check the temps on the condenser, if the condenser has gone bad you'll have a hot side and a cold side on it whereas it should be hot to ambient. Keep following the dischare pipe, if it suddenly gets cold then you have a blockage in that pipe.

next is the TX valve it could be stuck wide open and not throttling the flow and the last bit will be the evaporator bypassing internally. The Tx valve you might be able to sort with a gentle love tap and to check the evaporator bypassing touch the fat discharge pipe where it comes out of the fire wall if its cold then the problem is the evaporator bypassing internally which means you'll have a very small section of it getting really cold and the rest of it at ambient temperature.

good luck

[scarry]

What Dave said^^^^

Another thing you can do is find the receiver drier,should be at the front of the vehicle somewhere.It will have a sight glass in the top.With the compresser running,is the liquid bubbling or frothy or is the glass clear.if clear it could be full of liquid or totally empty.If frothy or bubbling,refrigerant may be low.

This may give you a clue as to what is going on.

[finallyrangie]

Thanks for the detailed replies, and quick, very much appreciated.

Electrics are fine clutch in and out as intended, the small pipe gets hot but the big one doesn't cool down, pulling the plug off of the low pressure switch stops the compressor,

Would I be correct in thinking that indicates that the compressor has lost it's squeeze, I have another one in the shed if that's the problem.

Looks like it's going to be another regas no matter what happens

Thanks again for all your help

[Blknight.aus]

no, if the skinny discharge pipe is getting hot and the electrics are all working then you have enough gas to at least allow the system to operate and enough compressor ability to raise the pressure enough for it to work at least marginally enough for further diagnostics.

next step is to find out how far things are getting along.

find the reciever drier, it should have a sight glass in it, (it may be painted over) whats that doing.

alternatively check how much of the condensor is getting heat on it if its not getting warm for at least half its area then you're probably looking at low gas.

you'll want to follow the path of the liquid refrigerent around the system to find out how far its getting before it goes from shedding heat to absorbing it. if it goes from shedding heat to absorbing heat in the condensor you have only 2 probably faults.

1. low gas
2. internally damaged condensor

the best method of checking the condensor is to stop all airflow over it (remove the fan from the engine and pull the fuses for the thermo fans) then with the AC on high run the engine at high idle while you measure the temps.

the last thing that comes to mind is..

is the heater coming on at the same time as the AC?

other than that yes you're up for a regas after repair. Its been a while but I've heard tell that some of the newer hydrocarbon based refrigerants along the lines of hychill-30 are not attracting as high a cost penalty for refil work as the orignal cfc refirgerents. IIRC Lotz-a-landies has a good deal more information about it.

I've also heard, but havent yet bothered to look at confirming, there are some new refirgerants coming out that may not require licenses to purchase or fill with for small quantities but are not 100% backwards compatible so you'll need to purge and setup with new oils.

[finallyrangie]

I admit to being out of my depth with aircon so please be gentle if I say something dumb!

The out pipe (small high pressure ) is getting hot, I have a diesel engine transplant so not everything is where it should be, but the pipe is hot until it goes into the radiator, then nothing as far as I can tell. I think I may have found a witness to the dye in the gas though , as long as it's green it looks like one of the crimp joints may be failing , so I may be short on gas, there is still some pressure, I pushed the valve on the filler, but maybe not enough to cool down .

Whatever happens I obviously need to fix the leak first, and I would never have seen it if I wasn't testing the heat of the pipes, so that's next.

Thanks for your help and support, I will let you know how it works out

Looks like a week with the windows down for me

[Blknight.aus]

by the sound of that if you have wetness around the joint on the small pipe to the condenser then youve lost enough gas to cause the system to not work effectively but retain enough pressure for the lp cut out to not stop the system. ALthough this can also be caused by a blockage in the condenser causing all of the refrigerant to be compressed into the outlet hose to the point where it hydraulics in the pump and the fitting gives out to relieve the over pressure until there is only enough left in the system to fill the hose. Rare but not totally unheard of

flex hoses failing at crimps or the hoses becoming porous is not uncommon and I would have expected that with the age of the vehicle that a nitrogen pressure test and run would have been done and the hoses checked as a matter of course.