Sounds like the guages are earthing out fully, pretty sure they rely on variable negative power to give a reading. The unit is fed constant positive (with ignition on) but the sender varies the negative (more negative (Earth) heats up the Bi-metal strip and give a higher reading on the guage), anyway, sounds like an earth short.

thanks levey, I will have a better look, it seems to be coming on and off now, so a bad earth mite be the go. Thanks everyone for your advice.

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