Focus Mk2 - Electrical Issue?

[nsushi33]

Hi All,

I'm hoping someone might be able to point me in the right direction on where to start with this. I've got a Focus Mk2 06 1.4 petrol. The issues started when my left hand rear brake light became dimmer than the other.  I changed the lights around to see if it was the bulb, and the issue stayed on the left hand side. The week after, whilst driving about 30ish, the engine stopped dead. I managed to pull over and tried to restart, but whenever I tried, the red light in the dash would just flash and the display would just show dashes - the engine would not even attempt to turn over. After about 10 mins of googling the issue, I locked/unlocked the doors and the engine restarted with no issues. A bit further down the road, and the powertrain light came on and the car went into limp home mode. I managed to get home and googled the issue but couldn't find anything obvious other than taking it to a garage to have a look at to read the code. I decided to go for a drive in the car to see if it did it again and it was fine - no powertrain light, no issues at all. A couple of weeks have gone by without issue (no lights, no issues)until today. Today, whilst driving around town again, all the lights illuminated on the dash, not just the power train light, and the speedo and rev counter dropped dead, but I was still able to drive the car. I've checked the battery which is reading at 12.6v, so my assumption is that it isn't the battery or alternator. Could I be looking at an earth fault?, or is this more likely to be a mechanical issue? There are no strange noises coming from car to suggest anything mechanical.

If someone with a bit more experience of these types of issues might be able to give some advice, it would be much appreciated.

Thanks in advance

 

[fiestaecoboostman]

I think you might be right 1st time, chec the earth strap / wire from the battery to the chasis. Could be loose or corroded.

[F0CUE]

Have heard that ford paint under where the earth is mounted from the battery which can cause issues. I would take it off and clean up under there and add some dielectric grease. 

[Ned_Mk2_1.8tdci]

Main earth strap is connected to the gearbox casing. Second earth strap is at the RH side. Check both. Also check local earth fort the rear lights as well ( in the bonnet, under the carpet).

[WireyWhenWet]

Two things one very very common to the mk2/2.5; cluster.

The main cluster is a known problem area whereby the soldered joints and lines on the actual PCB are known to crack with exposure to changing temps, its a relatively straightforward fix for someone with half an ounce of soldering ability but not one I'd suggest for the inexperienced DIY'er with no prior similar projects. Google mk2 focus cluster solder fault and you'll find aplenty of hits and videos on the topic.

 

Second and arguably the easier of the two, the symptoms you describe are EXACTLY how my 1.6 went when the Crank Position Sensor gave up. Random power offs, wierd warnings, etc. But for me no just 'dashes' on the dash, which would lead me to point more to the cluster fault. The sensor itself isn't difficult to get at, its a little tedious but can be done with the assistance of a nearby kerb to give you a bit of clearance to get under the front. Mine was caused by a very poor clutch change where the garage damaged various components, but ultimately loosened the wrong things which caused the actual mould that the sensor sits in to become loose and the bolt to go freeflight into the clutch housing.. Only around 7 quid a sensor for the 1.6, I wouldn't expect much more for the 1.4.

 

For reference, the sensor for mine looks like the pic, minus the banana bolt thats stuck to it.. (Sensor is a magnet so actually brought it out for me which saved a full take apart..)

Edited September 21, 2020 by WireyWhenWet
Added pic.

[nsushi33]

Hi All,

Just thought I'd come back and let you know the latest.

I managed to clean the earths in the engine bay and the ones in the boot. Unfortunately 10 mins down the road and the lights all came back on. I left the car for a bit and took it for the MOT, where the guy told me that the light was a known issue with the cluster (thanks WireyWhenWet 🙂 ), so I reflowed the solder joints in the cluster, and hey presto, the lights aren't coming on anymore 🙂

Unfortunately the dim rear brake light is still an issue, which I'm trying to solve, but at least the major one is fixed 🙂 

Thanks for all of your advice 🙂 

[mjt]

The brake light issue is almost certainly an earth fault. What happens is that the brake light on the affected side earths back through the tail light on that side and the tail light on the other side. The two tail lights in series reduce the voltage to the brake light. You don't notice the tail lights because the brake lights are brighter. This is shown in the left-hand diagram below.

This can be tested because if you put the sidelights on the brake light should go out completely as shown on the right: With the same voltage on both bulbs and no earth path no current flows through either bulb.

.

[DaveT70]

The brake light issue could also be a fault on the BCM board, MK2s are renowned for leaking water from the heater onto the bcm board and corroding it.

Disconnect the plugs on the bcm, one by one and see if you can see any corrosion on the terminals, top connections only.

You may get away with cleaning the terminals and everything will work fine again, if that's the case, wrap the BCM with cling film to prevent water ingress