New guy with AC problem

[MartynsAstra]

Hi,

Im Martyn and new to this forum though not to vehicle repair. I'm having trouble with my AC and hope someone can point me in the right direction as I'm currently scratching my head.

I have a 2000 Vauxhall/ GM Astra Mk4 that Ive been keeping going all these years. Recently I wanted to get the AC working so set about getting some new items as the old compressor bearings went kaput ( the noise was horrendous)

Replaced
* recon compressor from an AC refurb specialist
* replacement receiver/ dryer
*Pressure sensor

Condensor not too old...around 7 years old

I had it gassed initially , though there was no cold air, so took it to another place and it appears not enough weight of gas/ refrigerant was used ( should be around 600gm).
All was well as it could be from there, though the AC guys could only get around 13 degrees, stating that the system was inefficient and likely the evaporator was defective.....I managed to get some cleaning foam into the back of the evaporator to clean up the fins, should they have been blocked. I checked the drain off and I could see some small water drips from the external pipe when the AC was running.

So a few weeks passed like that. The other day I went to turn on the AC and there was no cold air, but a really pronounced noise through the air vents...almost like there was a leak echoing internally, or that the system was open somewhere inside...the noise got louder as I pressed the throttle...it was almost like I could hear the air inside...but behind the dash and through the air vent ( in the middle)...I hope that makes sense.

The system still has pressure...around 3.4 bar at idle, raising with revs

Below is a picture of my AC system.....i also found a spare expansion valve in my box of Astra stuff. ( Items 6/4 are pulse dampers..the evaporator is behind the dash where the high and low pressure sides converge)

Id be very grateful of any ideas or thoughts...

Kind regards

Martyn

[Cornbinder89]

OK, we can't "hear" what is happening, but vacuum leak in the control doors, and a Tx valve that is "trumpeting" are possibilities.
second, without an temp/pressure readings we can't do much.
A shop that is charging money to re-gas should be able to diagnose as well, you are paying them, they should do the work.
Age is not indication of condenser condition, but without pressure/temp readings there is nothing pointing to if that is a problem or not.
I rarely find Tx valves to be the problem.
We don't have that model in the US, but most A/C systems are similar.
It doesn't sound like you are set up to do A/C work, so you are going to have to rely on what a shop can do. Ask around and find a good shop.
Very hard to diagnose over the internet, and impossible without temp/pressure readings.

[MartynsAstra]

OK, we can't "hear" what is happening, but vacuum leak in the control doors, and a Tx valve that is "trumpeting" are possibilities.
second, without an temp/pressure readings we can't do much.
A shop that is charging money to re-gas should be able to diagnose as well, you are paying them, they should do the work.
Age is not indication of condenser condition, but without pressure/temp readings there is nothing pointing to if that is a problem or not.
I rarely find Tx valves to be the problem.
We don't have that model in the US, but most A/C systems are similar.
It doesn't sound like you are set up to do A/C work, so you are going to have to rely on what a shop can do. Ask around and find a good shop.
Very hard to diagnose over the internet, and impossible without temp/pressure readings.

Thanks Combinder for your reply.

I've just been out to take some data:-

Ambient outside temperature- 21.5 C
Inside Air temperature from fans at 750rpm idle (air recirculation on) - 27.0 C
AC pressure sensor WITHOUT compressor active - 2.34 bar
AC pressure sensor WITH compressor active ( throttle blipped 750-2000 rpm)- 3.25 bar
Inside Air temperature WITH compressor active after 2-3 minutes- 26.5C

Hope that makes sense...many thanks again for your reply.

Martyn

[Cornbinder89]

Really need high side as well as low side pressures. 2.34 if after sitting shows way too low, essentially empty, this for a system that has been sitting say overnight.
A/C pressure sensor have been known to be a problem, so gauge readings with a manifold set of mechanical gauges are needed to confirm sensor readings. Gauges also show things that can't be shown with a low side reading alone.
If you don't have the tools, you can't do the job. A/C work is not do it yourself friendly. A set of gauges, a vacuum pump, thermometer and a way to capture refrigerant removed are the minimum to diagnose. A scanner reading what the pressure sender say is not a substitute for the proper tools.

[MartynsAstra]

Really need high side as well as low side pressures. 2.34 if after sitting shows way too low, essentially empty, this for a system that has been sitting say overnight.
A/C pressure sensor have been known to be a problem, so gauge readings with a manifold set of mechanical gauges are needed to confirm sensor readings. Gauges also show things that can't be shown with a low side reading alone.
If you don't have the tools, you can't do the job. A/C work is not do it yourself friendly. A set of gauges, a vacuum pump, thermometer and a way to capture refrigerant removed are the minimum to diagnose. A scanner reading what the pressure sender say is not a substitute for the proper tools.

ok thank you for your reply!

Perhaps I am coming across as more ignorant than necessary. I certainly am aware that this isn't like cake baking with the kids on a Sunday afternoon. I'm a heavy plant mechanic by day and have very little to do with AC generally so my intention is to learn more about what is happening before spending more money.

thank you for your advice

[Cornbinder89]

With high and low side pressures, the temp of the air moving through the condenser, you can get an idea how well the system is working, in other words how efficient it is at moving heat.
Pressure readings equate to temp of the refrigerant at the point measured if the system has its proper charge amount. High side will show the condensing temp of the refrigerant, while low side will show the boiling point.
No where did I say they show the amount of refrigerant in the system, however. These pressures can be misleading if the amount of refrigerant in the system is wrong.