The fuel and coolant temperature gauges on my 760 don't work, except once in a blue moon (for a few minutes only).

I noted the manual says this is usually the voltage regulator on the rear of the instrument panel that causes the problem when both gauges fail, but (after much searching) I found a replacement regulator and changed it, but it still doesn't work. I've also cleaned the connections to the actual gauges with no results either. This is a really frustrating problem which leaves me driving blind in the fuel level and engine temperature department.

Any suggestions would be appreciated.