I don't understand Aux belts
 

Hi, I am trying to change the aux belt on my 2012 S40, but when searching online, there seems to be no single option? Autodoc, ECP etc list various sizes of belts for the alternator belt.

I have bought one from ECP as they recommended one they said would work, but I just don't think it's correct as it doesn't show as compatible on any website.

Car Spec:
Volvo S40 2012, 2.0 Petrol Manual /w AC.

I have the 705mm ac belt, the alternator belt from ECP is 1310mm.

Can anyone shed some light on this as I don't want to start taking belts off only to find its completely wrong.

I think the reason for the numerous options is that there have been a few revisions to the tensioner design over the production run.

As a 2012 model, yours likely came out of the factory with a fixed tensioner and a stretch belt, with a second stretch belt just for the AC compressor.

This turned out to be problematic, and Volvo started fitting a sprung tensioner with a normal belt when they came up for a belt change.

The original set up on mine only lasted 50k miles before it started rattling, and I replaced it with a kit from Volvo which contained the belts and a new tensioner.

So depending on the mileage, and if someone has changed the set up on yours, will dictate what you have.

If it's original, I would recommend getting a tensioner and belt kit, part number 9487168. Or, if your lucky, some has already fitted the new tensioner, and you just need belt number 9487317 for the alternator and 30777417 for the AC compressor

Absolute legend, very useful reply thank you!