hi my rev counter flickered and then went off panic set in thinking it was a electrical fault as i was doing a long trip down the m6 so i made a call to a friend and found out on my car which is a 300 tdi 1995 there is a white wire on the back of the alternator what does the rev counter and it had snapped repaired it and as worked 100 per cent since so just have a look to see if you have a white wire , if you have just see if its still attached to the alternator as they do go brittle hope this helps