Air Con Clutch not engaging, pressure & relay okay

[Boney25]

Hi all,

I’ve got a 2013 Ford Focus and have had an issue with my AC not working for a couple of weeks (only realised when the weather improved). I’ve tried quite a few different things but no luck. So far, I’ve:

·       Tested the AC clutch resistance;

·       Checked the continuity of the AC clutch wires, and AC pressure sensor wires back to fuse box;

·       Tested the AC clutch relay, and swapped with the horn relay;

·       Changed the AC pressure sensor;

·       Shorted the AC clutch relay connections to engage the clutch, which ran and blew cold air;

·       Checked the AC clutch fuse;

·       Checked the input voltage to the AC clutch when pressing the AC button on/off – no voltage change;

·       I have also been to Kwik fit twice to have gas levels checked (once before checking everything, and once after checking the above).

I can only assume that the car module which controls the AC isn’t sending the signal to engage the clutch. But I’m not sure why.

Could it be the module itself has a fault? Or is there another sensor which it takes information from to determine whether the AC clutch can be engaged, I've read about the evaporator temperature sensor?

I've checked for fault codes and the only one I have is u0422:84-2f, which is for the PCM receiving an invalid input from the BCM. Nothing is coming up for the AC circuit

I’ve spent countless hours trawling through forums and youtube, and now I’m at a loss; I really want to find the issue myself (well with some assistance) without going to a garage. I’d really appreciate any help or pointers to guide me to the next thing to check.

[Botus]

an AC clutch is something pre 2005,

most cars now, and indeed on my 2007 mk2 focus has an ALWAYS on constantly variable compressor, it has a swash plate and the load of the compressor is variable and altered by the engine management to reduce the load on hills, under hard acceleration and for conditions where full cold isn't requied

[Boney25]

That is peculiar. My AC compressor definitely has an electromagnet which engages/disengages from the pulley, which is constantly rotated by the drive belt.

I've also got a 2009 Fiesta, both have the 1.6 tdci engine, and I can hear and see the clutch engaging and disengaging as the pressure in the AC circuit rises.

Perhaps it is to do with the engine model?

[TomsFocus]

1.6 TDCi does have a compressor clutch.

Are you using Forscan to check for fault codes?  Climate circuit probably won't show on generic OBD.  Also is it electronic climate or just manual dials?

Does the engine cooling fan work?  Does the active grille shutter work?  Do you get correct ambient air temp readings?

[Boney25]

I haven't been using Forscan, but after doing some research I'm going to purchase the adapter and check what it says.

It is electronic climate control, and I believe the engine cooling fan works.

The active grille shutter and amb air temps though, I'm unsure. I guess the grille shutter is closed when cold and opens as the coolant temperature rises?

 

[troy45]

If you put the AC on full and run the engine with the bonnet open can you hear a loud clicking from the compressor clutch operating?

Maybe slightly different symptoms but on my ST I had issue where the AC would work initially then stopped once the car had run for a bit. Checked gas pressure expecting it to need a regas but that seemed ok so it left me stumped and I just left it a while.

Then at random I found via youtube videos it was due to AC clutch slipping - bit of work to pull the outer plate off the end of the compressor, remove a shim and refit it. Now works a treat.

Could be worth looking into further?

[TomsFocus]

20 hours ago, Boney25 said:

I haven't been using Forscan, but after doing some research I'm going to purchase the adapter and check what it says.

It is electronic climate control, and I believe the engine cooling fan works.

The active grille shutter and amb air temps though, I'm unsure. I guess the grille shutter is closed when cold and opens as the coolant temperature rises?

 

Ambient temp is the same as the dash shows, so as long as that's roughly right it should work.  It defaults to -40c when broken and the AC won't kick in that low.

The grille shutter spends most of it's time partially closed without the AC on, it's as much for aerodynamics (and reduced emissions) at speed as it is for keeping the engine at a decent temp.  Forscan will show if it's faulty, but you can also see it through the front grill.  If you can get an assistant to switch on the ignition while you look through, you should see it move.  

[Boney25]

I've now resolved the issue, thanks for everyone's input!

I used Forscan to check for fault codes and had B1B71 in the BCM, which is Evaporator Temperature Sensor - Signal Amplitude Greater Than Maximum.

I looked behind the cover under the glove box to check how easy it was to access the sensor. And thankfully, it was just a loose connector. I reattached the connector and the AC started working!

Thanks again!

[TomsFocus]

51 minutes ago, Boney25 said:

I've now resolved the issue, thanks for everyone's input!

I used Forscan to check for fault codes and had B1B71 in the BCM, which is Evaporator Temperature Sensor - Signal Amplitude Greater Than Maximum.

I looked behind the cover under the glove box to check how easy it was to access the sensor. And thankfully, it was just a loose connector. I reattached the connector and the AC started working!

Thanks again!

That's got to have been the cheapest AC fix on here for a while!