Hi i am hoping somebody here may be able to help me. i have a 2009 mk2 focus estate 1.8 tdci with normal air con. well at least its fitted but it doesnt work. compressor has been changed and known to be good and the system has been properly filled with gas. i have checked the relay and fuse under the bonnet and they are both fine however i have zero power at the relay. am i right in thinking this is a problem from the relay back to the switch in the car? 

i did have a look under the glovebox on that fuse box and noticed there appears to be some wires soldered in to the large plug on the right hand side of the box which i assume is from something thats now been removed. could this be causing an issue? i have no idea what that plug is for. it looks like the wires have just been removed and are not shorting out or anything but im not sure 

Does the cooling fan cut in after say 30 seconds when when you switch on the a/c?

Ideally you need to plug the vehicle in, check for any codes obviously.

If nothing obvious then i would do an active test on the cooling fan, does it run?

Check a/c pressure data, too much or not enough will have the same effect, a faulty pressure sensor could be telling the car its low on gas.

Does the switch light up?

One you can check at home and i appreciate you say you have a good used a/c compressor, is to unplug the compressor and wire up yourself a 12v headlamp bulb with 2 wires going straight into the harness multi plug, if it lights up when you switch on a/c then your compressor is no good.

18 hours ago, Ecosport2019 said:

Ideally you need to plug the vehicle in, check for any codes obviously.

If nothing obvious then i would do an active test on the cooling fan, does it run?

Check a/c pressure data, too much or not enough will have the same effect, a faulty pressure sensor could be telling the car its low on gas.

Does the switch light up?

One you can check at home and i appreciate you say you have a good used a/c compressor, is to unplug the compressor and wire up yourself a 12v headlamp bulb with 2 wires going straight into the harness multi plug, if it lights up when you switch on a/c then your compressor is no good.

I will have to order a cable and get Forscan to plug it in and see if I can find any codes or obvious issues then. 
 

the cooling fan I noticed starts to run as soon as the car is started is that fairly normal? 
 

the switch on the dash lights up but I’m not entirely sure that rules it out as not being a problem from what I’ve seen posted a couple of times. 
 

with the idea of plugging a bulb in to the compressor plug to see if it lights up there is no power running through it at all yet so I guess that one will come later on if I manage to get power sorted and it still doesn’t work after that 

Basically in general the older a/c systems will work on a fault hierarchy of system faults, for example if the pressure sensor is reading too high or low it will generally shut off the whole system, this can sometimes happen with the fan, but generally if the rest of the system is ok you will always get power and ground to the clutch on the compressor as older cars never really monitored this hence why the bulb works well as it also loads the system, so a dim bulb would show an earth or high resistance issue etc.

Good luck

On 10/4/2022 at 8:56 PM, Ecosport2019 said:

Ideally you need to plug the vehicle in, check for any codes obviously.

If nothing obvious then i would do an active test on the cooling fan, does it run?

Check a/c pressure data, too much or not enough will have the same effect, a faulty pressure sensor could be telling the car its low on gas.

Does the switch light up?

One you can check at home and i appreciate you say you have a good used a/c compressor, is to unplug the compressor and wire up yourself a 12v headlamp bulb with 2 wires going straight into the harness multi plug, if it lights up when you switch on a/c then your compressor is no good.

can I do all of these tests in Forscan? I’ve just taken delivery of a vlinker cable and about to download it but never used it before. thanks 

ok so i just plugged it in quickly with my very limited experience and managed to select air con , air con switch, and air con high pressure switch.

switch says no which i assume is a good thing and means it isnt faulty and then the other 3 all say on, but my air con isnt on nor working so not sure what thats worth! 

The other 3 what all say on?

Im not familiar with forscan only used it once to programme a camera.

Im sure someone will be kind enough to read and reply to this to assist you on how to check a/c pressure and to do an active test on the cooling fan .

26 minutes ago, Ecosport2019 said:

The other 3 what all say on?

Air con says on air con switch says on and air con drivers request says on too. 
 

I will have to try and have a better look at it and see if there is anything else I can see in there then. I can see the high pressure switch but not the low pressure I thought that one might be the better one to see