I suspect there is a break or bad connection in the wiring, you should have power at the wire at the sender WITH the ignition on, have you tried grounding this wire directly from the back of the cluster? The gauge should then read maximum, if this happens then you have a break in the wiring.

Yes the auxillary warning system flashes, if there is an open circuit, it will do this for around 10+ seconds.

Number plate lighting circuit is on same circuit as the panel lights, so if you have lost these as well you have a problem with this circuit, otherwise it may just be both bulbs have blown, we can easily test them.

Martin