Instrument Panel Bulb Too Hot

[sandbug]

My instrument panel bulb is very hot and bright! I converted to 12 volts negative, and got all the correct 12 volt bulbs. My instrument panel light bulb is too hot (very, very hot) and very bright. I even tried a 24 volt bulb, which brought down the brightness, but it too is hot. I saw something about an open ground. Could a ground somewhere be causing this? Right behind the bulb? How and where do I test?

Thanks!!!