I have nothing sensitive to add, but I'm sure it's all a sealed unit, it can't be repaired. The bulb probably contained a liquid or gas that changed pressure with temperature.
yea, i found that out today. auto-meter doesn't sell just the one gauge either, so i need to figure something else out. CRAP!
Good attitude to have. Too many people half-arse items like gauges, wiring, etc. There's a right and wrong way to do things even if most of the installation job will be covered up.
When you replace it, get an electric gauge and sending unit. You will appreciate the ability to route the wire the way you want, and the electric gauges are just as if not more accurate. I replaced a mechanical gauge after I broke the sensor, so I know how frustrating it is.
A good warning. I have a new mechanical gauge for my car. I planned on running the tube securely in the engine compt. along the valve cover (mines a 6) and looping any slack under the dash where it can't be seen.
I got an Autometer Phantom, and it is a really good gauge. You will have to also get the sender if it doesn't come with it (can't remember), but it is cheap and worth every cent. I use the 2 5/8" gauges, but they do come in the 2 1/16" also. My gauge was about $50.