For the last 4 months I've been having my battery light intermittently coming on and off. After testing my battery on numerous occasions the battery and alternator seemed fine. They are both only 2 and a half years old. Last night all power went and I was stranded. The Rac came and the battery wasn't charging, on a diagnostic machine I had the code P1246. With a baby due in the next 2 weeks I'm very reluctant to pay for a new alternator and a mobile mechanic to fit it if it's not the root issue as money is very very tight at the moment. Even the Rac mechanic wasn't convinced its the alternator that's caused the issue. Any help would be very much appreciated. If my wife goes into labour I just hope the ive got a fast taxi driver!!!!!!

2.5 years means nothing, either can fail 1 day after the warranty, if in warranty BONUS , get them both checked and if ok, i'd take a closer look at the loom, possible broken wire or coroded connection.

Is this a 2008 Focus? , whack the top of the dash above the instrument cluster, engine on/running.

if spurious warnings happen, suspect dry joints in the cluster.

my son’s 2008 st had this fault last year