rpm meter keeps at zero

As I cannot see any glow plug light on your instrument panel, not having the complete picture does not help; I am going to assume your vehicle is a Diesel. In which case the amplifier is usually the culprit here. It is mounted on the inner left wing (looking at the vehicle from behind, forwards). The unit is black and cylindrical and has a screw top which can be removed. Also you will find it near or next to the glow plug relay. 

First measure is to unscrew the amplifier and pull off hard the top. If this separates, you will see a silicone packed top. Taking a small to medium sized piece of paper, fold it into quarter and pack this in between the screw cap and the silicone and re-tighten. This may or may not solve your rev counter issue, failing this if you are inclined and have the equipment to dismantle and try to re-solder any dry soldering. Alternatively buy anew. The problem could lie behind the rev counter but this rare.

  eric if you tap / slap the top of instrument  cluster  work or not??

   if it bursts in to life try this

    http://www.gwoa.co.uk/content/temp-fuel-gauge-jump-when-lights-turn

​     it fixed my rpm counter as well

      adrian