Hi.  My 03 fusion has just developed a fault with the headlights. The one works fine butthe othe is very dim and no full beam.  I've checked all the blade fuses and changed the bulb but it's still the same. Any idea what else I can check?

Sounds like a bad connection.  Definitely worth checking the plug for corrosion and then looking for a nearby earth point.  If nothing obvious, you'll need to check wiring with a multimeter.

top left of passenger fusebox there are two relays

Relay 243 activates sidelight and dip beams

relay 244 activates both main beams on one output, so if one is working and the other isn't  then the relay shouldn't be at fault.

You could swap relay 243 & 244 to prove that relay is ok but more likely to be wiring / connection problem in engine compartment as Tom suggests

Black earths, E3 or E4 would be my first port of call for inspection.

 

Check out intensity of sidelight with and without dip/MB.

A fault on a common earth will dim sidelight, a fault only on H4 connection should not affect sidelight brilliance

Similarly see if indicator is affected

E3 behind LH headlamp,

E4 RH inner wing

Thanks for the replies. I'll check the earth tomorrow and swap the relays. I'll let you know if I have any joy 😉

I gave up looking for the fault and drove to the local mechanics about 20mins away. By the time I got there and turned the lights on, they worked!  Still working now after a few days, so it seems to have fixed itself.

Thanks for the help 🙂

If you have been hand ragging the cables, and it's just a poor earthing connection then it could rectify itself, but possibly return in future.