Hi all,

Last chance saloon for my Focus MK2 55 Titanium Petrol. 

Randomly battery light comes on, abs and brake lights come on, speedo stops working, dash goes off completely - more recently headlights blowing.

Last Friday driving on the motorway the lmain beams blew for the second time in a fortnight - RAC changed the lamps, we're driving and the headlights are getting brighter and then dimmer.

The dashboard itself was resoldered recently as garage assumed it was the common issue with dry solder.

Video of dashboard issue occuring.

 

cheapy obd shows nothing at  moment but did show speed sensor fault a while back. Both garages I have taken it to say it's not worth diagnosing properly and to scrap it! (This was prior to the headlight issue which may be a new clue)

Any thoughts? 

 

 

I think if the headlights get too bright and blow it must be a fault with the voltage regulator inside the alternator.

Years (and years and years) ago I had a Yugo 511 (you never see a Yugo now) and the headlamps would keep going brighter than they should, not now and then but in a steady cycle for about one second once every three seconds all the time the headlamps were on.  This was fixed by replacing the alternator.

The battery is 12 volts (well actually a car battery is about 12.6 volts when charged and left to rest a bit). The alternator can produce loads of volts and is usually regulated to about 14 volts by the regulator built into the alternator housing. 

Check all connections/wiring on the alternator and the battery (including the other end of the battery earth lead). An intermittent bad battery connection could also cause voltage spikes I think, if it quickly disconnects/connects going over bumps or whatever. 

I cant see how it can be anything other than

a) needs new alternator

b) wiring/connector on alternator

c) wiring/connections on battery

I can see why it was thought to be the instrument cluster, but it would not explain the headlamps going too bright and blowing

7 hours ago, ezman said:

the lmain beams blew for the second time in a fortnight

The only way a bulb can blow early like that (if not faulty) is a high voltage from the alternator. Voltages too high or too low can upset the electronics and cause resets and shut-downs.

So, like Isetta, prime suspects are alternator, and related wiring.

On these cars, the alternator does not normally regulate the voltage itself, it sends a signal to the ECU, and gets a signal back, so the ECU is in overall control. There is a three pin plug on the alternator for this purpose. However, it is still circuitry in the alternator that actually does the control, which can fail. You just have to add the ECU to alternator wiring connections to the possible failure list.

I would add to Isetta's list the heavy earth wire from the battery to the engine bell housing, as this is the alternator main earth connection to the battery. Though if the car always starts ok, it suggests this wire is ok. Intermittent electrical faults can be very odd though, and work fine most of the time.

I think I would monitor the system voltage, ideally both at a power point (cigar lighter) and at the battery direct. Then with the engine idling, wiggle various suspect wires about to see if a fault happened.

Some places can test alternators, but an intermittent fault may not show up on a brief test. Gremlins always seem to hide when they know they are being searched for!

21 hours ago, Tdci-Peter said:

Gremlins always seem to hide when they know they are being searched for!

How very true . . .