What's wrong with my Ford Focus?
- Tuesday, 29 April 2008
I can only guess, but I think your problem lies in the rather rapid development of car electronics. Current generation cars use the engine management computer (EMC) to monitor all the electronic functions. If your trailer connections were wired into the car using the old Scotchlock into the wiring harness method, the EMC is probably reading the switching on one of the caravan’s indicators as a dead short in the indicator circuit and switching off the feed.
With modern cars the safest way to wire in the trailer lights is with a dedicated wiring harness called a Vehicle Specific Harness (VSH). Sometimes just plugging in the VSH is sufficient to tell the EMC that a caravan is attached. Sometimes the EMC has to be told what the VSH message means, and this is done by minor re-programming. With popular cars the fitter may already have the computer programming on his laptop computer, but even if he has to download a patch, it only takes a few minutes.
From our reader’s letters we know that some don’t like the additional cost of VSH, but it is so quick and easy to fit that the total cost of VSH and fitting isn’t significantly different to Scotchlocking in bare wires.
