Aircon not working

[MartinJG]

Hi team. Hope everyone is bearing up.

Just noticed recently with this hot spell that the aircon is not working. Here is my troubleshooting tick list.

Both fans start up as normal but stay on and only stop when the aircon is switched off. The clutch on the compressor is definitely engaging/disengaging when switched on and off. I can hear the click and load on the engine at idle and the revs drop slightly so that suggests it is working. Not surprisingly, the low pressure and high pressure pipework remains at ambientish temp. I have checked the radiator/condenser. No sign of obvious damage but I don't think that means much. Could be a hidden leak anywhere on the loop.

I had a re gas last year (May) carried out at ATS Euromaster. The aircon has been run routinely since then. The technician reckoned the pressure was just below normal before he drained and refilled but that was a year ago. It could have sprung a leak since then. I obviously need to get the car pressure checked as soon as poss but in the meantime, are there any additional obvious DIY checks that I can do myself.

PS - I know the relay switch can be an issue but since the clutch and fans are operating it seems unlikely unless I have overlooked something technical.

[culzean]

You seem to have covered pretty much everything. Aircon relay more likely to stick closed than open due to contact arcing ( clutch solenoid is an inductive load ) and weak return spring.

The system will not run if gas pressure drops too low, so the fact that fans are running and clutch pulling in means gas is at least minimum level,  which may be too low to cool effectively.   Aircon is sensitive to correct gas amount for proper operation due to balance of compression and expansion in system.   IIRC aircon with low gas is prone to condensor freezing up due to gas expanding too quicky.

[MartinJG]

Thanks for the vote of confidence. I was rather hoping you would point out the error of my ways and a quick fix would be in order...

[guest4871]

Have you checked the temperature coming out of the vents with a thermometer? Should IIRC be 7C.

I find, in hot weather, that the A/C sometimes reaches its capacity to cool the car - or even, simply, the vents are not properly adjusted.

It should be cooler again tomorrow. See if the ambient temperature change produces a result before you go in for any "heavy engineering" solution 

[culzean]

OP said both the low and high pressure pipes are at ambient, if aircon was working properly the hp pipe should be hot even if aircon has reached its capacity and not cooling very well ..  sounds like gas needs checking to me.

The interlock to gas pressure is to protect compressor from running without gas ( and the gas has lubricant in it ) does not guarantee that there is enough gas for proper operation and optimum cooling.

[VicW]

A proper aircon service doesn't just bung some more gas in the system. It evacuates the system and measures what comes out. This is compared with the amount that should be in there from tables that should be available to the operator for your car. The result gives an idea of leak rate and possible faults. The system is then recharged including lubricant for the pump and seals. If a leak is suspected some luminous dye will be included to help trace the leak.
Your problem Martin still sounds like low gas content.

Vic.

[olduser1]

Most issues can be traced back to damaged condensor, leaks at the last joint worked on and lack of use.

[MartinJG]

Thanks to all for feedback. Pressure test seems the next logical step.