So far, we have come across three types of E30 taillights. The obvious two differences are between the through-1987 vs. 1988-and-on cars — though the E30 convertible kept the earlier type of taillight throughout its production run, which ended in 1993.
As far as we can tell, all taillights use three 21 Watt light bulbs on each side, and one 10 Watt light bulb.
The units consist of a colored plastic lens with an integral backing plate that has holes in it for the light bulbs. Another backing plate, that BMW calls “Covering Cap,” contains the integrated wiring and the light bulbs, and the entire covering cap fits onto the lens unit from behind. Thoughtfully designed, this fitment uses hand-tightening fasteners so you don’t need a screwdriver to change out your rear light bulbs.
The earlier units come in two styles as to the covering cap. One style has its 10 Watt light bulb mounted sideways next to a white-opaque window that helps illuminates the inside of the trunk when the light bulb is activated.
As far as we can tell, the earlier-style covering caps are identical between the driver side and the passenger side; the later-style covering caps are different as to the driver side vs. the passenger side.