intermittent prob

[fluidityfreerun]

hi all, i have a strange occurence every so often on my 02 diesel berlingo, sometimes when engine is warm the diesel heater icon does not light, when this happens the engine starts, however doesnt sound 100% and the rev counter stops working and also the temp gauge does not work.
at a later point when turning key, diesel heater icon works, goes out and everything back to normal.
i changed the relay in engine compartment, but this still sometimes occurs,,, any thoughts
gareth