Air conditioning issue

[djwazza68]

I have no air conditioning; I'm pretty sure I have a leak, but I can't get the clutch to engage to try to refill it. What can I pressurise the system to whilst the compressor isn't running?

My clutch gap is also 0.75mm (ie at least .45mm too large), will it prevent me from pushing the clutch closed to test if the compressor is actually broken? I was trying the broom stick option earlier with no joy, but may invest in the 3 tie-rap solution if it will help.

Any comments gladly received; I'm keen to avoid expensive shop refill fault finding and stick to DIY if possible, especially as I have a nearly full can of STP that I can use to top up.

[4x4]

The system needs to be full of gas before the compressor will kick into life. Best take it to a professional and have them check for leaks, they will vacuum test and if all good refill adding the correct amount of gas, oil and dye to allow them to check for any leaks in the future

[cheshired5]

Check for voltage at the clutch solenoid power plug.
If you're getting system voltage but no clutch engagement, the clutch gap is the most likely cause especially with current pretty warm ambient temps and especially if the clutch engages on a cold engine but not later when warmed up.

[Clogs]

I thought the air con was losing gas so wouldn't engage, but it was the clutch gap. Look on Youtube or the forum for a cheap solution that doesn't require removal of the compressor. The compressor will never engage with a 0.75mm gap.

There are three spaces on the three springs at the face of the compressor, through which one can thread a bit of thick single strand copper wire... if too thick, you can hammer it flatter to make the clutch gap fit. Other suggestions are plastic ties, but they only come in one thickness, whereas copper wire can be slimmed down so the gap is correct. This job was an hour or so.

This has been working for the best part of a year. Volvo dealers would just put in a new compressor, but I had a new compressor a couple of years ago and the clutch obviously wore down a lot more quickly than it should. Replacing shims means removing the compressor and that is a faff.

[djwazza68]

Thanks all, I've shimmed it to 0.4mm using the cable-tie method and now await a regas and leak check; it's definitely leaking, so I assume replacing all O-rings is the first port of call once I find out where it's leaking from?

BTW it doesn't engage at all, even with the correct gap; so once it's re-gassed I assume it should prove whether the compressor is knackered.

[cheshired5]

Originally Posted by cheshired5

Check for voltage at the clutch solenoid power plug.

I'll suggest this again.
If you have no power there, the pressure sensor is the next check where you can bridge the contacts to see if the clutch will then engage.

Low gas will cause the pressure switch not to send power to the clutch solenoid.
Correct gas but no clutch solenoid power suggests a faulty pressure switch.

[djwazza68]

Air con guy locally ran a vacuum test on it for 30 minutes; no leaks. Regassed for £65 now blowing ice cold, all components appear to be working perfectly! It must have been empty for at least 5 years; a glowing indictment of the components originally fitted 22 years and 200,000 miles ago!

[Willow place]

How can a Sealed system lose its Gas/ Fluid etc , my central heating system doesn't have that problem .

[cheshired5]

Originally Posted by Willow place

How can a Sealed system lose its Gas/ Fluid etc , my central heating system doesn't have that problem .

Your central heating joints are static and live in an environment with a temperature range of maybe 30°C

Car AC joints and components live in an environment which can easily range from -20° to >80°C and be subjected intense vibration so it's little wonder they can lose their integrity over the years.

[Martin Cox]

Your central heating system is probably just filled with liquid and is unlikely to operate at much more than atmospheric pressure. An air conditioning system is mostly filled with pressurized gas and a relatively small amount of liquid. The operating pressure is probably of the order of 10 times atmospheric pressure.

Gas is much better at finding leaks than liquid.

By necessity, the compressor on a car air conditioning system has a seal through which a rotating shaft passes to operate the pump internals. This seal will leak but this can be minimised by running the aircon regularly which distributes refrigerant oil around the system whichstops the seals from drying out and becoming leaky. This applies to the other seals where various components are joined together.

By contrast a domestic central heating pump can be designed so that the stator is on the outside in the dry with the rotor and pump entirely submerged in the liquid and no seal needed since the moving part of the motor is on the wet side.

Car air conditioning systems also include flexible hoses and these too can be slightly porous allowing the gas to slowly leak away. Again running the system regularly keeps them coated with oil which makes them less leaky.

Having said that, a system in good order should hold its charge for a few years but it will, inevitably, leak.

Fridges and freezers don't usually leak because the compressors are hermetically sealed and there are no flexible pipes.

Martin