Hey all.

I've just bought myself a 64 plate fiesta Zetec. 70000 on the clock. 

I noticed something this afternoon that I wanted to check.  On idle, I had the AC on and it sort of changed the noise of the engine. Made it louder. No clicking or anything, just a louder purr /whir of the engine. If I switched the AC off that noise went away. I noticed the RPM twitch slightly too.

This is, honestly, the first car I've not bought on Facebook marketplace that's not already dying and the first car that has working AC so I've no clue wether this is normal or not. 

 

Cheers.

 

Oh.  I also wanted to ask, if possible how long it should take to reach optimum temperature on a normal 10 °c day.   I noticed it took me about 5-10 minutes, and takes a while to cool to cold after I stop. 

The engine sound does change when the air con is switched on as it puts a load on the engine. Also the radiator fan should start running with the air con switched on and the car stationary. You should hear a slight change in sound from the engine and the sound of the fan too. Whether the fan always runs may depend on the air temperature but I can't remember for certain. On mine I do hear a click as I switch on the air con from the engine bay as the air con clutch clicks in. It does certainly sound as though your air con is working from what you describe. The engine revs will change a little as the air con is switched on and off due to the change in load put on the engine.

Incidentally there will be a switch which cuts off the air con if it's short of refrigerant to protect the compressor so if it's running then it means you have enough refrigerant in the system.

47 minutes ago, Matt Alsop said:

The engine sound does change when the air con is switched on as it puts a load on the engine. Also the radiator fan should start running with the air con switched on and the car stationary. You should hear a slight change in sound from the engine and the sound of the fan too. Whether the fan always runs may depend on the air temperature but I can't remember for certain. On mine I do hear a click as I switch on the air con from the engine bay as the air con clutch clicks in. It does certainly sound as though your air con is working from what you describe. The engine revs will change a little as the air con is switched on and off due to the change in load put on the engine.

Incidentally there will be a switch which cuts off the air con if it's short of refrigerant to protect the compressor so if it's running then it means you have enough refrigerant in the system.

Thanks so much for this!

I was just tooling around with the sound system and plugging my phone in and stuff to make it all work (idle of course) as this is a whole new world for me.  I must have accidentally switched the AC on and the noise made me jump and go into instant panic mode, because this car is my baby.

 

Thanks so much for putting my mind at ease!

The 5 to 10 minutes to warm up is right too at this time of year assuming you are asking about the engine warming up. It depends on the journey. If I start with a slow drive through town it takes 10 minutes to reach normal engine temperature. If I head out straight to the dual carriageway it's more like just 5 minutes as I'm up to 60mph almost straight away.

2 hours ago, Matt Alsop said:

The 5 to 10 minutes to warm up is right too at this time of year assuming you are asking about the engine warming up. It depends on the journey. If I start with a slow drive through town it takes 10 minutes to reach normal engine temperature. If I head out straight to the dual carriageway it's more like just 5 minutes as I'm up to 60mph almost straight away.

Cool.  Yeah I drive slowly through a small village, which is a lot of hills and stuff.

But I'm so used to an 18 year old diesel engine that took around 10 minutes to even start heating up, that it surprised me.  You're amazing thanks!