1974 280 electrical short

[mormit]

I'm helping a friend out with his 280 which did not pass inspection due to the turn signals not working. Didn't have my multimeter on hand when I looked at the car today so I'll be looking at it this weekend. I'd like to find an electrical drawing unless anyone has a suggestion from the following symptoms.

Fuse#5 (8A) was blown so I replaced it and it blew almost immediatly upon turning on the ignition. Some notes:
*Turn signals were not on so they were not or should not have been drawing amperage.
*Fuel gauge is on the same fuse. Upon turning on the ignition, the indicator shot up very quickly. Faster and more jerking than I would expect.

Thanks

[mercmad6.3]

sounds like something as simple as the plug on the fuel tank sender unit has been damaged by someone carry a large loose object in the trunk....or as in my case I found a large stereo amp in a car that had screwed into the trunk with the screws running into the fuel tank sender.
Also indicates that something is "going to earth " via the gauge circuit.check the earth connections in the trunk,(the Brown wires which are screwed in various places to the body) some may have been cut off. in error.
Remove all the lenses and ensure that the bulbs are clean and have good contacts .On the rear of the indicator lights make sure the plugs are pushed fully home.
has anyone played around under the dash and conected a stereo etc to the hot wire of the flasher unit?.
Is there a trailer hitch with a plug for lights etc.I always find faults in these and consider them as prime candidates for checking first.