1.8k rev counter stopped working

[D7PNY]

Was working fine when I parked it up a few weeks ago to fit my new seats and cage but when I started up today for first time in a few weeks the rev counter is doing nothing.

Still got power to gauge as lights etc still working but needle doing nothing.

Got a busy week at work and have a sprint next weekend so need to get it sorted asap. Are there any common issues with the Caterham rev counters? Just a sensor? Where would it be as I've tried tracing wires quickly but not having much luck.

Dave