[Engine] Alternator

[Lost in translation]

Hello I have a berlingo xtr 2011 115 bhp model I recently bought I noticed after a week the wipers were a bit slow so I bought myself a battery/ alternator tester  its charging at 12.9v but When I go down hill or coast in gear it shoots up to 14.8 and everything springs in to life  .
I read about problems with the negative battery lead so I cleaned sanded and greased it. It helped but the problem is still  exists I went to the dealer who straight away without testing said its my alternator and wants almost £600   The battery Was changed in nov 17  I am thinking about changing the aux belt  and tensioner next as I havent got £600  the car has 59,000 miles 
Anybody had similar problems?

[Art b]

Hello I have a berlingo xtr 2011 115 bhp model I recently bought I noticed after a week the wipers were a bit slow so I bought myself a battery/ alternator tester  its charging at 12.9v but When I go down hill or coast in gear it shoots up to 14.8 and everything springs in to life  .
I read about problems with the negative battery lead so I cleaned sanded and greased it. It helped but the problem is still  exists I went to the dealer who straight away without testing said its my alternator and wants almost £600   The battery Was changed in nov 17  I am thinking about changing the aux belt  and tensioner next as I havent got £600  the car has 59,000 miles 
Anybody had similar problems?

I bought a near new one from a breakers for £28 delivered 

On eBay with a 90day warranty...

[geoff]

They are not called " Main Stealers " for nothing !!!

I'd certainly fit an alternator from a scrap vehicle, the old one could even be fixed for modest money, eg new brush and diode pack, and kept as a spare. Alternators can often be resued on a DIY basis.

[brajomobil]

There are 9 diodes on alternator. On yours probably 2-3 are bad.
It works but can't deliver full current at low revs.
You can rebuild the alternator for cheap or buy one from scrapers.

Best regards,
brajomobil

[Lost in translation]

There are 9 diodes on alternator. On yours probably 2-3 are bad.
It works but can't deliver full current at low revs.
You can rebuild the alternator for cheap or buy one from scrapers.

Best regards,
brajomobil

Thanks thats makes more sense I am going to replace the belt as it Looks very worn and cracked  I am looking for a 2nd hand alternator  and have a go at rebuilding mine