Hiya. First time poster.

 

Got a 2008 Mk2 Focus, and bought on the cheap as a run around. The only bug was that you had to manually unlock the car and get the key in the ignition in about 10s before the horn started beeping. 

 

This morning went to unlock it to get something out, and seemed the battery was dead. Nothing, would turn over, was like the car was bricked. The dash was super dim, and thought I'd left a light on or something to drain the battery. Then my partner noticed the headlights were on and stayed on, even with the key out. Eventually they went out. Then I've noticed some ticking from a relay under the passenger footwell. Its all really bizarre and probably not making much sense, but wondered if its a battery issue or a immobiliser issue. Had a rapidly flashing red light (i assume thats the immobiliser) on the top centre of the dash. Now no headlight sticking on. 

I'm all at sea with this one and would appreciate any insight!

7 minutes ago, lukalukaluka said:

 Had a rapidly flashing red light (i assume thats the immobiliser) on the top centre of the dash.

Hi Luke, welcome. I can confirm that the flashing red light is the immobilser at work. When it's flashing, the car won't start. Many gremlins can show themself if the battery isn't fully charged, in this colder weather it's worth putting the battery on a charge if you have one. A static reading on it should be about 12.8v when it's on full beans. Of course, other suggestions will be along shortly...

Thanks. I've got a mate with a battery tester coming shortly so should be able to diagnose that. Have checked the cabin lights and the horn and seems that its properly dead. Any other info or suggestions is very welcome. Thanks for the feedback.

Under the glovebox is the GEM. It looks like a fuse box but it contains the relays and a circuit board with computer chips on. It is really a mini computer that controls the electrical stuff on the car. The are loads of plugs going into it. These can be affected by passenger feet knocking them. Also the GEM sometimes get water in them which causes problems.  The GEM and ECU and instrument cluster all speak to each other with a constant flow of computer data   over the canbus wires. It’s all very complicated.