Flickering lights

I have a 2011 Ford Focus 1.6 diesel that I have owned for just over a year and I noticed, while parked in front of a wall in the dark, that the sidelights were flickering. This only happens when the engine is running and affects all external lights and occasionally the radio display screen when the RPM rises then drops again. It looks to me like aircon ripple, but I am not a competent electrician, especially on modern vehicles.

The dealership from which I bought the car investigated the issue with the assistance of Ford Technical. They had the car for three weeks, then told me that it was a characteristic of the model. Ford would only say that they couldn’t confirm the dealership’s opinion and couldn’t offer me any further support. At the time of the dealership investigating, it was covered by a warranty which has now run out.

I would greatly appreciate your help in getting to the root of the problem. John Wooding The charging system on your Focus is controlled by the powertrain control module (PCM) and the system of intelligent charging adjusts the charge according to the temperature and condition of the battery. It will also deactivate high-drain systems such as the HRW, air-conditioning and heated front screen if the voltage drops below an acceptable level.

This complex system is not without its faults, but as Ford Technical have checked the vehicle they should have carried out all the relevant checks to diagnose any problems. These would include removing and cleaning all the connections, and checking the output of the alternator and the PCM voltages. The battery condition should also have been confirmed as a faulty battery would very likely give the symptoms you have described. I would also note that if the original battery is fitted, it may be due for replacement. If a replacement battery has been fitted, then I would check that it is a silver cadmiumtype as required by the charging system, although I would have expected Ford Technical to have covered these points.

Ford vehicles have been subject to this sort of flickering in the past and this was eventually dealt with by a technical service bulletin (TSB 053/2001). On that occasion, the fault was due to a high resistance in the wiring harness from the central junction box to the B+ terminal of the alternator, and also a high resistance in the 7.5A fuse. This caused the alternator output to pulse, resulting in the flickering lights. The service bulletin advised that a new feed from the battery cable to the alternator should be fitted.

According to a number of Ford owners, the alternator is not up to the job. Although it is operating within the given specification, the flickering is the result of inadequate power. Some owners have reported eliminating the problem by fitting a replacement alternator.