changing alternator belt tensioner? - richT
My local independent changed the alternator on my 96 VW Polo 1.9D a couple of months ago because it was overcharging. Last weekend an almighty racket started up and a different garage diagnosed problems with the belt driving the alternator and the water pump. The belt was jumping really badly, creating metal and carbon dust everywhere and was trashing the water pump pulley. This they thought had been caused by the wrong alternator being fitted. The alternator pulley is wider (5 teeth wide) than the water pump pulley (4 teeth wide) and they thought that this was causing the belt to jump.

So, I took the car back to the first garage. They are now claiming after long discussions this week with VW that the alternator is in fact the correct one and that the difference in pulley width will not cause the belt to jump. Instead, they think it is due to the belt tensioner seizing up.

My questions are 1. does this seem a likely cause? and 2. should they not have changed the tensioner as a matter of course when they changed the alternator? I am prepared to row about the money if they should have changed it before because the alternator and labour cost me 350 quid - the diesel takes 3.5 hours labour vs 1 hour for the petrol engine. Ouch.

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