Aircon has suddenly stopped working

MarkMas

Chief pedant
Messages
8,779
The aircon on my 2009 QP V was working just fine on Saturday, but on Sunday - no cold air. Have fiddled about with all the buttons/settings, but nothing - just warm air, and 28 degrees in the car! Any ideas what could cause a sudden failure like this, and any suggestions for getting it fixed (ideally in the Bristol/Swindon area)? Do air con specialists understand Maseratis?
 

spkennyuk

Member
Messages
5,919
A good aircon engineer will be able to diagnose the problem. Essentially there are 5 main reasons why you would suddenly loose aircon assuming the belt driving the compressor is still intact.

1. Low refrigerant gas. If there is insuffient pressure in the system then the low pressure switch will not let the clutch on the compressor engage.

2. Faulty low pressure or high pressure switch. Again the system will not allow the compressor clutch to engage.

3. There will be a fuse and a relay that support the aircon system. Check in your manual for the fuse number to see if it has blown. If the fuse is intact then check the relay is clean dry and hasnt burnt out. Most cars you can hear the relay click when you turn the aircon on but im sure somebody with a QP will advise. You can test the relay with a multimeter.

4. Aircon coolant loss due to leak in the system. Aircon radiator or burst hose for example. The aircon engineer will try and pull a vacuum on your system. If they can not pull a vacuum to recover the old refrigerant gas then there is a physical leak in the system. The next stage would be to put a UV dye in the system to find the leak if it isnt already obvious. Again the aircon engineer can do this to diagnose the fault.

5. The aircon compressor has failed. Which your then looking at a replacement or repair if clutch packs are available.

The only other thing apart from faulty electrics or faulty cabin switch that i can think of is if the dryer unit is comprimised. Either a rupture or full of water through a leak on the system.

Check the fuse and relay 1st and then go from there.
 

mattjevans

Junior Member
Messages
386
Mine works intermittently - annoyingly on the hottest days it seems to blow warm, but if its below 25 seems to be OK. Must get it looked at but for now I just put the windows down...
 

spkennyuk

Member
Messages
5,919
Mine works intermittently - annoyingly on the hottest days it seems to blow warm, but if its below 25 seems to be OK. Must get it looked at but for now I just put the windows down...

That sounds like the pressure sensors are shutting the compressor off.

The pressure in the system would change with the ambient temperature.

If the refrigerant gas level in your system is slightly lower or higher than it should be then on the warmer days the pressure in the system can fall outside the allowed parameters.

Yours could be as simple as having the refrigerant gas recharged to fix the problem.

Is the correct outside temperature displayed in the cabin when it stops working ?

If its not then your outside air temperature sensor could be the fault.

After that your most likely cause would be a fault on the low or high pressure sensor switches.
 

voicey

Member
Messages
660
It could also be the TGK valve. Have you drained the battery or switched the power off recently?
 

Zep

Moderator
Messages
9,098
For my money you are short of refrigerant. As the temperature rises the compressor has to attain a higher pressure for the refrigerant to condense. The higher pressure needs more refrigerant so it reduces the pressure in the low side tripping the LP switch and stopping the compressor.

Leak check and recharge I'm afraid.

The cost of R134a has tripled in the last 3 months so get the best deal you can...!
 

BennyD

Sea Urchin Pate
Messages
14,992
If it suddenly stops working it may be one of the metal pipes under the engine has worn a hole in it. That's what happened to me and the repair is a ball-ache; all the front and headlights have to come off and than it's a lot of p!ssing about with rotten and furry aluminium with corroded fasteners. Then a quick rebuild and a re-gas. I hope it's something a lot simpler. Good luck!
 

mattjevans

Junior Member
Messages
386
That sounds like the pressure sensors are shutting the compressor off.

The pressure in the system would change with the ambient temperature.

If the refrigerant gas level in your system is slightly lower or higher than it should be then on the warmer days the pressure in the system can fall outside the allowed parameters.

Yours could be as simple as having the refrigerant gas recharged to fix the problem.

Is the correct outside temperature displayed in the cabin when it stops working ?

If its not then your outside air temperature sensor could be the fault.

After that your most likely cause would be a fault on the low or high pressure sensor switches.

Outside air temp reads fine. First port of call is a recharge. Will any decent mobile aircon tech be able to do it ?
 

MarkMas

Chief pedant
Messages
8,779
... the hub has sheared off the front of the compressor. .... So I probably need a new compressor, unless they can magically re-attach it.
My local, non specialist garage did a fast job of sourcing a new Delphi compressor and fitting it, ready for my trip this weekend, but £820 is a lot to pay for cold air.
 

conaero

Forum Owner
Messages
34,582
Just so you know, I saw MAF yesterday at Ace, his AC has been broken for a while.

He finally got round to taking to be looked at, and it was over gassed!

Took it out and replaced with the correct amount and it fired right up!
 

ChrissGT

Member
Messages
341
My compressor us replaced and gas qas added, around 750grams i think. As it turns out its not blowing cold when outside temp is above 20 celsius.

So im trying to figure out what the correct amount of refrigerant should be on a 2007 GT. I found posts that reference a manual which states 600-650 grams and i found a chart saying 1000 grams. Is there anyone with a working aircon that knows what the 'correct' amount is.
 

Zep

Moderator
Messages
9,098
My manual says 600 grams, but it may be different for your car.

Other things that can give the sort of symptoms you have are:

Blocked drier - was it replaced?
Failing expansion valve
Blocked or dirty condenser on the air side
A refrigerant leak - a small leak will slowly reduce the amount of refrigerant in the system reducing the max operating temperature
 

SJX

Junior Member
Messages
81
It could also be the TGK valve. Have you drained the battery or switched the power off recently?
I have just changed the battery recently and just realised air con not working, I had assumed I need a regas, can this valve be reset or checked, i’ll pop it to local specialist if need be.
 

GDL

Junior Member
Messages
147
I have a fault that has materialised since the compressor was replaced on my 3200.
Most days the compressor will engage and disengage every few seconds.
Gas level is spot on (750g for the 3200).
This only started since the compressor was replaced.
Any thoughts please?

Edit - Apologies for posting in this forum. I arrived here via search and didn't realise I was in the wrong place
 
Last edited:

stevo

Member
Messages
361
The aircon on my 2009 QP V was working just fine on Saturday, but on Sunday - no cold air. Have fiddled about with all the buttons/settings, but nothing - just warm air, and 28 degrees in the car! Any ideas what could cause a sudden failure like this, and any suggestions for getting it fixed (ideally in the Bristol/Swindon area)? Do air con specialists understand Maseratis?
I had the same problem and found the clutch had broken off the compressor. Apparently this is a common fault easy to check by just looking at front of compressor. New one was only £260.

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