Temp and fuel gauge stop working

[House]

It's not really bothering me that much but every now and then my temp and fuel gauge stop working. Reaching up behind the dash and fiddling with the fuel gauge seems to sort it and sometimes a dash bash will fix it for a while. Any ideas? I'm sure I've read somewhere that it could be a voltage regulator but I'd never be able to find it or fix it without instruction.

[shamm]

It's a small rectangular metal box which plugs into the back of the dash.
It may just be bad contacts so if you can reach it then pulling it in and out a few times may sort it.