i've seen it happen once before and heard of it many times. i believe u could have a dodgy earth on the back of the clocks, and yes i'm afraid u would have to take them out to investigate, but the whole dash doesn't have to come out.
To get the clocks out remove the steering wheel (its not neccessary but makes things easier), then all the switches, heater control knobs, stereo, plastic surround, and then u should be able to see the two screws that hold in the clocks. Once u have the screws out u have to reach around the back of the clocks and disconnect the speedo cable..... after all that i think u should be able to lift the clocks out!! But its been a while so i might of missed out something.
Of course dont do any of that until ur sure the fault actually lies with clocks..... I'm sure some more people will post their opinions... eventually.
Anyways hope that hasn't depressed you... and good luck.
