Car air conditioning woes

[szrdave]

I've been going round in circles for the past few summers trying to get the AC on my car working, I've replaced the air dryer, most of the hoses, and all of the o-rings up to and including the expansion valve.

I took the car back at the end of last week to have the system leak tested and re-gassed, it finally passed the leak test! Jumped in and turned the AC on, lovely cool air. Started driving home, and a couple of minutes later...hmm, no longer feels so cool. By the time I got home, AC on or off made no difference.

Went out today, and exactly the same. Starts off nice and cool, after a minute or so it begins to warm up. 

Things I have noticed:

Upon first press of the button the discharge pipe gets very hot to the touch and the suction pipe very cold. Both pipes entering the cabin after the expansion valve get cold and cold air comes out of the vents. The radiator fan does not start until after a minute or so, it then cycles on and off with longer pauses than run time.

After a few minutes the discharge pipe loses a lot of it's heat and the suction pipe is no longer as cold, the temperature of the cabin vents is cool rather than cold.

The compressor clutch remains engaged and the radiator fan continues to cycle as above.

Any suggestions on what I could check next? When the car is outside in the carpark at work and the sun is shining it's like an oven inside, I've stopped using it when the weather is hot.

[TLRS]

22 minutes ago, szrdave said:

I've been going round in circles for the past few summers trying to get the AC on my car working, I've replaced the air dryer, most of the hoses, and all of the o-rings up to and including the expansion valve.

I took the car back at the end of last week to have the system leak tested and re-gassed, it finally passed the leak test! Jumped in and turned the AC on, lovely cool air. Started driving home, and a couple of minutes later...hmm, no longer feels so cool. By the time I got home, AC on or off made no difference.

Went out today, and exactly the same. Starts off nice and cool, after a minute or so it begins to warm up. 

Things I have noticed:

Upon first press of the button the discharge pipe gets very hot to the touch and the suction pipe very cold. Both pipes entering the cabin after the expansion valve get cold and cold air comes out of the vents. The radiator fan does not start until after a minute or so, it then cycles on and off with longer pauses than run time.

After a few minutes the discharge pipe loses a lot of it's heat and the suction pipe is no longer as cold, the temperature of the cabin vents is cool rather than cold.

The compressor clutch remains engaged and the radiator fan continues to cycle as above.

Any suggestions on what I could check next? When the car is outside in the carpark at work and the sun is shining it's like an oven inside, I've stopped using it when the weather is hot.

Can't quite wrap my head around all your data.. but is it possible there's too little gas in the system? Or the heater is fighting your aircon?

[2moto]

Sounds like to expansion valve is not doing its job, or the compressor not producing sufficient output pressure when it warms up. More likely the compressor, I suspect. 

[szrdave]

21 hours ago, TLRS said:

Can't quite wrap my head around all your data.. but is it possible there's too little gas in the system? Or the heater is fighting your aircon?

Gas should be fine, as it was just filled and the clutch won't engage if the pressure is too low. 

Don't think it's the heater either, as the AC lines in the engine bay loose their temperature 

[szrdave]

14 hours ago, 2moto said:

Sounds like to expansion valve is not doing its job, or the compressor not producing sufficient output pressure when it warms up. More likely the compressor, I suspect. 

Pain in the arse if it's either of those, as I'll have to get the system emptied before changing them. Is there a way to narrow it down?

I think I'll probably leave it until winter and change both. Then the complete AC system will be new (and I'll be a grand and a half into it on a car worth about 5 😅)

[TLRS]

Generally you can see externally what a valve is doing, right? Never been near one from a car ac ever, but there's always a rod or axle innit?

[2moto]

8 hours ago, szrdave said:

Pain in the arse if it's either of those, as I'll have to get the system emptied before changing them. Is there a way to narrow it down?

I think I'll probably leave it until winter and change both. Then the complete AC system will be new (and I'll be a grand and a half into it on a car worth about 5 😅)

One of those AC service machines should be able to diagnose it. I'd say it's more likely be the compressor. 

[davecara]

Get it diagnosed by a specialist, you'll be going around in circles for ages otherwise. Also, get it pressure AND vaccuum tested with nitrogen. The normal AC machines only vaccuum test so if youve got a dicky seal you'll be back to square one. Whereabout in the world are you?

[szrdave]

Thanks for all the replies, it seems to have fixed itself!

I had noticed before it was making some whooshing, swooshing and squeaking sounds every now and again. Driving home yesterday I turned the AC on, expecting to get a few minutes of cool, and it just kept going all the way home. No noises now so I wonder if the expansion valve was a bit sticky and has freed up.

 

[TLRS]

Nice!