Hi, My 1.6 '99 Marea has a jumpy, intermittent tacho.
Any ideas as to an obvious fix?

Could be a few things so checking it out will not be easy.
Assuming all the other instruments are ok it is probably not a connection problem on the back of the instrument pod but you could if you want to take the pod out and make sure all the plugs are seated properly and the connections are clean it will rule it out.
The rpm sensor is mounted on a bracket on the off side of the engine next to the crankshaft pully. Make sure the sensor is clean and the connections are ok, the sensor operates by sensing the teeth on the back of the pully passing it and also feeds TDC info to the ecu. You can check the airgap between the sensor and the top of the teeth, it should be between 0.5 and 1.5 mm. If you take the sensor off do not remove the bracket it sits in as doing so will mean special tools to reset it correctly.
The other possibility is of course a faulty tacho.
Hope the above makes sense

Thanks for that, so the tacho runs off the crank sensor? Hmm, as the car runs nicely, probably not that? Oh well, the pod will have to come out sooner or later...

I had this prob' many moons ago on my Marea and it turned out to be a loose block connecter on the back of the dash, they sometimes work themselves loose over time, abit of WD40 and clean up sorted it fo me.

Right, Weekend = cam belt, oil change, brake disks & pads (If the discs get here!) and if I have any energy left, airbag and dash. Watch this space!

mine did this on the new set of clocks i fitted.everynow and then it stopped working and sat at 0,then itd bounce right round lol took the plugs out and back in and has been fine since