AC not working. Where to start?
 

The AC hasn't worked properly since I had the car.

In the last week it's worked for about 20 seconds. (Nice and cold with AC smell).

The facts:

1. No fault on VIDA. Gas pressure all good.

2. When it does work it's only for a minute or 2.

3. It is not dependent on wether the engine is hot or cold.

4. I can hear the clutch engagement click.

5. There is a whining noise just perceptible when the clutch is engaged. But after that, I can't hear if it's still engaged because of the noise of the climate fan.

Maybe the clutch is slipping. Does anyone know what the clutch gap should be?

Any other logical steps I can take to isolate the fault?:

ie: testing sensors, relays etc.

How many sensors are there? Where are they?

Where is the relay?

Does the ac have a dedicated manifold pressure sensor to cut it under acceleration? If so, where is it?

Any tips on testing various components with a multimeter would be most welcome.

Sounds like you have covered the basics...

Next I would have someone operate the switch in the car whilst you look at the compressor. The pulley will always spin with the engine but you should be able to see the clutch plate on the front start to turn when the system is switched on and you hear the click.

If that doesn't spin with the pully consistently for minutes on end, check the clutch gap (articles on here and vids on YouTube) and power to the clutch solenoid.

If it does spin then I think you need to take it to an A/C specialist (not just a top up service like KwikFit or Halfords) and get the high and low side pressures monitored, it may be the compressor is not pumping.

May help : https://www.motorverso.com/ac-low-si...sure-too-high/

Thanks! The link looks very good. I'll have an in depth look later this evening.

Remember since 2010 it is illegal for anyone to tamper with the gas side of the system .. Only people with the relevant Qualifications are allowed to . A hefty max £40,000 fine ..

Thanks, but I think the gas side is OK since occasionally when it works it's as cold as it should be.

a few simple checks at the relay should find out what is going on , check the compressor cluuch gap with some feeler blades , it should be as small as possible 👍
Does it always work from cold first thing in the morning ? If so it could be the gap because when the clutch warms up the resistance of the holding coil increases reducing current and hence holding power .

Could not deduce any pattern to the random operation. It only worked about 2% of the time.

Got a reputable ac expert to do a diagnostic on it. The conclusion was an intermittent valve within the compressor.

He recommend I get a new compressor rather than a repair kit, reconditioned or second hand, since he had experienced more problems than not with these options.

He emptied the system for me so I can do the installation. So now the hunt is on for a compressor. There seem to be many choices of new compressors ranging from about £225 for a pattern part to £360 for OEM to whatever Volvo charge.

They all seem to have a 2 year guarantee. Cash is a bit scarce, so not really sure which way to go.

My experience with this aircon problem was not Volvo but Honda and the Honda main dealer sent me to the auto aircon specialists that they themselves used and they recommended a factory re-manufactured compressor at about £350 rather than a new Honda supplied unit at nearly £700. I had no problems with the unit. I can understand the possibility of bad tolerances with a workshop repaired unit but factory re-manufacturing uses the main casings and replaces all the working parts with new ones to original spec. I've done the same in the past with brake calipers.

Update:

Advice to get a new compressor and fit myself was insufficient since there was no instruction on adding oil, how much, checking for swarf in the system etc etc.

Went to another company. They diagnosed the same fault in the compressor internal valve. (£60)

Supplied and fitted new compressor, including testing and VAT. (£768).

Since found out that modern compressors have a solenoid valve plugged into the side which fails easily if not regularly used. If I had had the knowledge I could have replaced it myself for about £30 and then paid for the re-gas.

But is was not to be......

Moral of the story: My understanding is that modern air compressors have this solenoid valve to micro regulate the gas flow for the purpose of fuel saving rather than just on/off with the clutch. So given that they are more economical to use, it seems it is best to keep the climate control permanently on.

PS. Stretch belt was original dated 22 06 2010 and 155k miles. Replaced it with nice cheap Volvo part at only £41 including VAT and 10% forum discount. I paid less than that for my first car in 1986. A Morris Marina for £40!

True, today variable capacity compressors are used to not waste fuel unnecessarily.
On/off was back in the 700-series days.