I have an intermittent (actually about 50/50) problem with the brake lights & tail lights on my EF XR.
With the headlights on the 2 taillamps will go out but the spoiler & the lamp in the rear parcel shelf have just a dull glow.When the brakes are applied these two lights wll glow only slightly brighter..Any ideas where I should start looking?

sounds like a bad earth.