Weird Electrical Gremlin

[Ratmick]

I've got a 2010 (first registered May 2011) LV MKII TDCi Focus.

Turn it on when it's cold, starts fine and for about 5-10s the tacho and radio don't work. Once you sit there and the arbitrary time limit expires the needle and radio spring into action.

In a linked sympton I've also had a couple of instances where the radio would lock up and go dead and the only thing that would work was the clock. First time I fixed this by pulling out the radio fuse. The second time left it overnight and it had forgiven me by the morning.

FWIW when I'm talking cold, not only it hasn't been started for a while, it's now -2C in the morning.

If the car is warm then it doesn't do it.

It still has its original Ford battery so I'm wondering whether it's coming up to the 'I'm going to die on you when you most need me and nothing is open except the local servo, sucka' point of its lifecycle...or whether this is symptomatic of something else. I was going to try a car reset and pull the positive battery terminal off for a while...

Anyone ever had this before...or anything like it?

[Peter B - CV8]

Battery is on it's last legs. The BCM shuts off electrical supply to selected components until the battery has enough charge to power everything.

[Ratmick]

Battery died in the bottom last Sunday.

I normally garage my Focus in my 45'x25' shed but for some reason I left the door open Saturday night and it got down to -2C.

That seems to have been the straw that broke the camel's back, car refused to start Sunday evening when I had to drive my missus' daughter to the airport so she could fly out to the UK.

Lucky I have a backup BA MkII Fairmont, but remember what I said about the car dying when I was going to need it the most ?

Anyway new Bosch S3+ battery and the problem has disappeared.