During the split second before the fuse blows, the lights work...the open door chime too. They wouldn't work, would they? If there was a problem there?
We found the problem fuse last week and replaced it...I drove it for two days before it shorted out again. Now it just shorts out right away.
Have you tried isolating the short -- figure out what is on that circuit, disconnect all and add back one at a time until the fuse blows. Might need a repair manual.
The alternative: remove one circuit at a time until the fuse doesn't blow anymore. Requires more fuses.
Once you have figured out which circuit is causing the short then could be the device (light, radio, etc.) on that circuit or the wiring to the device. A volt meter/ohm meter would be handy at this point -- check resistance between wiring to ground. etc.
Tougher if it is shorting intermittently.
It sounds like you have an overload and not a direct short circuit.
Are you sure that the proper size fuse is being used?
Actually, give me the model and year, if it's a 1992 to 2002 I can look it up and tell you what size fuse it should be and everything that's on that circuit.
I have all the Ford/Lincoln/Mercury shop manuals and wiring diagrams for those years.