306 hdi alternator change: should I DIY? - pugoilburner
Just after some reassurance; I'm about to have a go at replacing the alternator and am wondering if I should just cough up and pay a prof.
I'm fairly happy that I'll end up with a pile of bits on the floor but am more concerned about how easy it is to gett the correct tension back in the belt. Is this just a case of getting the positioning right on the bracket thingy?

Any advice would be greatly recieved.

306 hdi alternator change: should I DIY? - TurboD
If you have done one before, then follow that process, but with modrn cars be wary of fouling electronics. disconnect battery etc.
as for tension , make sure it is like it is now.
But how do you know it's bust?, have you a meter? Is it the windings or justthe control pack?
You need a manual really before meddling, otherwise it could cost you.
Normally a fairly easy job on a motor
306 hdi alternator change: should I DIY? - dieselhead
It's a bit awkward because of lack of space so you need to be agile. The tension setting is easy as it's a spring loaded jockey wheel arrangement which needs to be levered away with a socket if i remember correctly. Also make a note of how the drivebelt is routed as it's quite complicated on the hdi. I would check the terminals aren't corroded before replacing.
306 hdi alternator change: should I DIY? - LeePower
If its the spring loaded tensioner get a 4 mm allen key / drill bit & once the tension is off use the handy lock hole in the bottom right hand corner to insert your allen key / drill bit in to lock the tensioner off.
306 hdi alternator change: should I DIY? - Crinkly Dave
I have avoided responding until a couple of Pug experts came along. On an old 1.9 like mine this is a doddle, as there is so much space and a screw tensioner. The only problem is the bottom bolt which can stick. Can do in 15 minutes, including post-job checks. Obviously a little more difficult on the HDi, but the Haynes manual or similar should make this straightforward.

But are you sure it is the alternator? If your mechanical knowledge is such that you are concerned about the job, how sure are you about the diagnosis (as you haven't mentioned symptoms). You may be better going to a small independent autoelectrician for diagnosis and swap. The price should be less than a dealer by a massive margin, and you can witness it. Even Halfords (pause for gasp from Backroomers) do this sort of stuff now, and their charges are not that terrible as it is a fixed price usually (wish I had let them do the Punto diesel one)