Problem now sorted. LEDs in the cluster had damp on the circuit board and the protective circuitry was spotting a short caused by this and switching the circuit off. The flash was this process in action. Clever designers eh! It appears post 2005 XC 70s (and others) were installed with this protectiv...

Thanks for that info (re: auto shutdown of circuit due to a short being detected). After a bit of a struggle managed to remove the light cluster and discovered the LEDs circuit board was wet. Dried it out and lo! Lights! Both position lights came back to life. Can't say the same for the LEDs though....

Upon turning the car on both rear offside position lights flash then immediately go out and stay out. Bulbs OK, checked and changed, fuse OK, checked and changed. Power must get there and contacts must be OK to make them flash. All other position lights OK, all other bulbs in this cluster OK apart f...

Both rear offside sidelights (position lights) flash when I turn the car on, then immediately go off. Bulbs checked and changed, fuse checked and changed. Earth and power supply must be OK to make them flash. All other position lights working fine. All other lights working fine, including the lights...