Rev counter doesn't work

A few weeks ago i had stripped the dash out and got everything working that didn't work before. I have started the golf 2day to find out the rev counter doesn't work.

What are the first and most likely things to check before taking out half the dash and fitting new clocks.

Cheers luke

wiring to clocks , give the plug a wiggle . could also be a wire off the coil .

Red/Black wire to the negative of the coil?