Posting in this forum also posted in the S80 forum without reply. It's a 2001 (Y) S80 D5 although this could be something on any car...

The background is that, a few months ago the alternator failed and has been replaced with a new Lucas unit. It has been checked on a voltmeter and also on VIDA and the output is 14 volts. Anyway, since the alt fail and subsequent replacement, whenever I brake I get the "Check brake lights" warning message which goes off when I'm not on the brake. Also, if I switch the headlights on I get the Position light warning (I can't recall the actual wording but it's the one that means one of the lights is out). Again, when I switch the lights off the message goes off ... just as well because that is now an automatic MOT fail.

Anway, I have checked and replaced all bulbs and cleaned the contacts. I have had VIDA plugged in and no messages/codes are showing that can be cleared and reset. I have checked the relays, disconnected the battery and still the messages appear.

Has anyone ever encountered this and, if yes, what is the solution?

Thanks for reading and for any proven solutions.

 

wonder if you have a cable resistance issue - clean/tighten terminals at the alternator, battery, ground strap etc?

 

Hello and thank you for taking the time to reply. I had assumed that, as the alternator had been replaced, the terminals would be OK. Likewise, the battery but I'll give them all a second look over. For cleaning, do you suggest a fluid? Which one would you recommend? Also, would you say a rub down with a cloth or scrub with a toothbrush or something? Please forgive my ignorance... and thanks again.