Hi Guys,

Being that this is such a lovely day today i turned on my Air Con and after 3/4 Seconds i heard and felt through my pedal a big Clunking Sound, it only Clunked once and the Air Con is working perfectly fine and im getting cold air through.

I don't think this is a normal sound for it to do, i was stationary at the time stuck in traffic after driving for roughly 20 minutes.

Hope i can sort this.

Thanks

Ed

they all do that its the pump starting

Yeah I believe its the air con clutch engaging... oh how I want my air con working full pelt right now!!!

Thanks for replying guys, the sound just sounds like a part of my car has just detached itself from the car, I really dont think it should make such a big clunking sound!

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the CMAX before clunked the air con so much I often thought I had been shunted! then it sounded like a vacuum cleaner under the bonnet!

Exactly what im getting! My car vibrates quite alot also

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Yeah, its not uncommon for the clutch to be heavy when engaging, shows that its still got plenty of bite! the vibration could be as small as an engine mount.

the CMAX before clunked the air con so much I often thought I had been shunted! then it sounded like a vacuum cleaner under the bonnet!

Mine is exactly like this. Very loud clunk then vacuum cleaner!

Was a lifesaver yesterday, would have been very uncomfortable otherwise!

Ok so I dont have to worry about it then! Bring on the heat! I notice it takes abit of power out of the engine too...not too much thankfully

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Few revs is nornal but I might take mine to a garage tomorrow, I want my air con back lol

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Ok so I dont have to worry about it then! Bring on the heat! I notice it takes abit of power out of the engine too...not too much thankfully

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The AC pump/ gubbins weighs 11 kilos - part of the AC is permenantly connected to the engine, and turns even when the AC is off (the pump pulley) this part weighs about a kilo (Mk3 Mondeo, sama as mk1/mk2 Focus)

The pump is a significant load - if you had one in your hands it would be hard to turn - its no surprise their is a clunk when the AC os switched on

The AC on can have a signnificant effect on MPG around town/ stop/start driving or when accelerating - it can impact performance as well - surprisingly, at a constant speed (eg, crusing on the m-way) it has little effect on MPG

Older car AC systems would take a few HP out of the engine (does not sound much but is a lot at tickover, low revs) - later designs are lighter/ more compact /draw less power/ have less of a negative effect on MPG, but do not go as cold/ are not as powerful as older AC systems

Few revs is nornal but I might take mine to a garage tomorrow, I want my air con back lol

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Hopefully it will just need the refrigerant topped up

Ive stripped out my AC out but its a bit colder up here and i keep the windows open a little now i have fitted air deflectors - if the car is sitting in the sun a while i open up the doors a minite before i get in - these things make a big difference

I only miss the AC 2 or 3 months out of 12 tops & the rest of the time i have the extra performance/ economy + its another thing that can't fail and the AUX belt never rattles now

Sadly not the case in mine, the refrigerant is mostly there, he topped it up a fraction then it worked now it's gone, I hope mine is just a pressure switch or sensor but the eatc diagnostics didn't show an error and nothing on the obd so it needs plugging in. Going to a garage tomorrow hopefully go through it and get their opinion

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Thank god I'm not the only one. Mine clunks too. However not always. And when it does it's on start up. Cheers