I have been struggling for 5 hours on a similar problem, but worse.

The light will blink crasy erraticaly for no reason, i mean will even pulse
with the engine rpm at start up, after the engine start, it will do all kind
of crasy thing... of course every wire, plug connector, relay have been
replace/check. From the engine bay to the cluster. Even the 2 plug going to
the relay and the other one unplug, this is still happening. So i pulled the
yellow and the blue one out of the cluster connector and i still have the
problem... so you will say cluster! but no, i have a spare one and smae
stuff is happening. So the conclusion, one of the other 10 or so wire is
making a short and that light react to it!!!

The van is an 84.

So today i should find more and i will post about it.

Ben