Condenser fan not coming on when ac is on

[timtom5000]

Hi,

My ac isn't working on my ford focus Mk3 2012 Europe.

I first checked the compressor and the belt and both fine.  Then I took it for a re-gas.  The garage also did a pressure test and it came out fine.

Just a week later the air is blowing warm again.  This time I checked the fan on the condenser and noticed the fan wasn't on.  I checked the relay diagram and found 3 "cooling fan" relays.  I've swapped them all out and nothing has changed.  (Could do with knowing which cooling fan relay is for the AC system). Then I found the there is a sensor on the high side of the gas that switches on the fans.  I've taken the switch plug out and cleaned the contacts and still no change.

Offer any advice before I take it to the garage?

Thanks

 

[WireyWhenWet]

From memory the AC compressor won't engage if the car detects a temperature at 6°c or below to prevent any damage to seals, etc.

Does the car read outside air temps correctly? I think theres a small nub sensor on the underside of the passenger (UK)/ left wing mirror, ensure that is clean and not waterlogged.

Not quite related but a possible thing to check as I've seen online someone had an issue where the sensor was reading correctly when the car was turned on, but it wouldn't read any changes in temps throughout that journey. It turned out to be a bit of water that had got on the inside from when it was jet washed - He took the mirror apart some and dried it all, and between it drying off and the wiring being disturbed that seemed to resolve the fault - Not for AC, but for a faulty temp sensor.

Hopefully it's as simple as that!

[timtom5000]

The compressor clutch engages and starts turning the compressor so surely it can't be what you mentioned wirey?  But funny that you mention the left wing mirror.  Mine is damaged from the previous owner so I wonder if the sensor you mentioned is damaged too... I'll go check now.  But my clutch is still engaging so I'd be surprised from what you've said if it was that.

[nicam49]

It won't engage if the pressure switch detects insufficient pressure in the system. You need to get it checked again, it's not unusual for the condenser in a car the age of yours to corrode and become leaky. If you took it to a 'proper' a/c place, they would have regassed it and included lube and  a fluorescent dye to make  leak detection under UV light possible. 

[n_hudson]

I bet you have a small hole in the ac condenser. Buy a cheap uv torch and look for a nice shiny green. I had mine refilled and 2 weeks later filled again. The clutch would work but no cold air, it also made a hissing noise from the vents. The machine kept saying it was fine, even had a hydrogen test (I think?) but neither picked up the holes until I looked myself with a torch. Needless to say I asked for a refund after spending nearly £100 on tests and refills.