Strange Behaviour from Instrument Cluster Backlight

[Motorhole]

So I've had this issue for a while but driving for a while in the dark yesterday (doesn't often get driven at night!) helped me observe this a little bit.

Cold start up, the speedo and fuel gauge were backlit, but not the tacho and temp gauge. After about 40 mins on the road...hey, I have full backlighting! Great. Stop at a services. Come back 10 minutes later, no backlighting at all. Then again, some 40 mins driving, the tachi and temp gauge lighting comes in but not the speedo and fuel.

Reads like a loose connection, but the behaviour of the backlighting (if it's working) ALWAYS being off after a break is consistent.

Any ideas?

[Brianmoooore]

You have a blown bulb. As simple as that!
The filament has broken, but the two ends are near each other, and vibrating about as the car moves. If they happen to touch, a current flows, and a magnetic field is created, which holds the two ends of the broken filament together until the lights are turned off, or the cat hits a pothole big enough to break the magnetic bond.

[Motorhole]

That's interesting, thanks. New bulbs it is.