1992 240 glimmering upshift indicator light?

dmg4 · Post by **dmg4** » 11 Feb 2012, 14:46

Here's a new one (for me). The indicator light in the instrument cluster (arrow) to indicate that the transmission is restricted to 3rd gear is glimmering, but the transmission shifts normally, and the "3rd gear button" on the side of the gearshift knob works just fine. The light is not really bright, as it would be in normal operation, nor does it ever turn off, irrespective of the switch position.

I know I can fix this by placing a piece of black tape over the light

, but what are the likely causes, and does anyone have some suggestions for a step by step process to isolate the fault?

Post by **billofdurham** » 13 Feb 2012, 11:51

The lamp is powered by a yellow/red lead from terminal 87a of the overdrive relay. It is possible that the relay is starting to fail. Also possible is a chafed wire to the lamp running to earth.

Bill.

dmg4 · Post by **dmg4** » 13 Feb 2012, 14:10

Hmmm... I think there is a red/yellow lead that runs to the large multi-pin recepticle on the upper back of the instrument panel. The bulb base is twisted into the cluster circuit board, so there's no wire to it directly. If I understand correctly then, there is a wire possibly chaffed that is either the red/yellow lead entering the back of the above recepticle, or perhaps between the relay and another component. How could I diagnose a chaffed wire? Continuity? Voltage across a bridge as follows: Using a multitester set to read volts DC, what should I get on the red/yellow lead if I run it to earth?

I was monkeying around with removing the shift knob last month to replace a trim piece, and had to solder the wires back to the OD switch. Might there be a loose wire/short there? Is the cheapest and easiest diagnosis to purchase and try a new relay and see if the light goes out?