I have a Ford Focus 1.6 petrol (2001) and have recently been experiencing starting problems with it. I assumed it was starter motor, but now I'm not so sure as it started first time the following day, but when I put my lights on it cut out.

I noticed the alternator was hot and put a tester on the battery to check, but it did not indicate that the alternator was faulty. I buy a new alternator does the diode come with it? I have been told this could be causing the fault too.