Got my retest for my MOT tomorrow last chance before I have to pay again. The problem is my alternator is not charging the battery. I have just swapped alternators over with my mates (thanks Stoo) and I know this is working but still no charge going to the battery. So its down to wiring I know the main feed to the battery is ok but as for the other smaller wire what do these do and is there anyway of checking these...? Please help as it looks like im heading for a late one

Oh its a Mk2 Xr2 with ERST engine and alternator

 

the little wire basically tells the alternator how much juice it needs to supply. it goes through the light on the dash somehow and somehow 'excites' the alternator into action.

if the resistance in the loop is different on your xr2 to what it would be on the ERST, this could mean that the alternator doesn't 'know' that your battery is low and needs charging.

done know how to test or rectify this though.

bttt for clever electrical folk