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Megger
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100 Posts
Discussion Starter · #1 ·
Hi,

I've had a problem with the aircon on my 2007 Mk3 Ghia (2L petrol) for some months, but it's not been too much of a nuisance over winter.

I spent a few hours trying to work through it yesterday, with reference to every AC thread I could find on here.

What I've found is that the control system is partially working, but never getting to the point of trying to engage the compressor clutch.

Checking at the low & high pressure switches, the low pressure switch is OK and providing a feed to the high pressure switch - I get 12V on two pins on the four pin high pressure switch connector with it unplugged.

That seems to show there is nothing amiss with the system gas charge.

Reconnecting the HP switch connector when the AC is supposed to be running, I hear a click and the radiator fan either starts or speeds up, there is a change in tone (not sure which over the engine noise and belt idler pulley squeak...)

However, no increase in idle speed with that, or when turning the AC on & off with the climate controls??

I've seen that mentioned as a prerequisite for the AC clutch etc.

Also, the AC still does not work at motorway speeds.

It seems something is preventing the overall startup sequence getting past a certain point, but I just do not know what and have not been able to find any mention of a similar fault.

Also, I've seen mention of the "AC Clutch relay" and that it's controlled from the ECU or whatever, with nothing else in the clutch circuit.

But I cannot find any such relay in the Mk3 fusebox and relay information in the Fordwiki?

The only part listed is a diode, which I'd guess is used as a flywheel diode to prevent back emf spikes or arcing?

I was going to change the relay & try a temporary bypass to verify the clutch wiring - but can't locate the thing.

(PS I'm well aware of the clutch shim problem, I have checked for voltage at the compressor when it first stopped working).

The climate control panel in the car passes its self test with no errors and the heating does regulate temperature, which I think rules out a cabin air sensor fault?

I'm stuck.

Any further ideas or info appreciated!

Robert.
 

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Megger
Joined
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100 Posts
Discussion Starter · #3 ·
Hi,

The feed via the low and high pressure cutout switches is OK, so it's seeing the pressures as OK regardless, based on everything I can find in other threads on here.

The compressor should cycle dependant on temperature and pressures, but it should come on immediately when the aircon is first turned on, with the temperature to the "low" setting.

Something I forgot to mention in the previous post - the heater blower does also switch to high speed when the AC is turned on.
 

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Megger
Joined
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100 Posts
Discussion Starter · #4 ·
Does anyone have a wiring diagram that shows the source of the power feed to the AC clutch, for the Mk3 with climate controls?

Or preferably a full diagram with the pressure switches etc. as well?

I just cannot find any info on that at all.

Thanks, Robert.
 

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Megger
Joined
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100 Posts
Discussion Starter · #5 ·
Wiring diagram located and problem solved!

It seems relay K32, the "Wide open throttle" relay, shown as a normally closed contact in just about every generic car air conditioning wiring diagram on the internet, is in fact the air con compressor clutch relay on the Mondeo and is a normally-open type.

The relay contacts are fed with 12V fia fuse F31 and directly control the clutch.

F82, mentioned frequently due to it popping with faulty heated washer nozzles & knocking out the A/C and cruise control, seems in practice to supply for the A/C control electronics.

F31, also listed as just "Air conditioning", is actually the fuse for the clutch circuit and nothing else; it feeds K32.

That fuse had failed; it was somewhat corroded looking so possibly just died of old age.

With a new 7.5A fuse fitted, it's worked perfectly on about a 30 minute test.
 
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