Cat 277 MTL electrical trouble

[BrianCinNC]

I'm hoping someone has some input on a problem I'm having with my 2003 Cat 277 MTL. In the past few weeks my ignition fuse has blown a few times for no apparent reason while operating the machine. Today the machine died while operating just like other times when the fuse has blown (indicator lights all off, machine is dead), except this time the fuse wasn't blown. It was hot however, and when I put it back in and turned the key to "run" for a moment it got warm again. I hit the socket with some contact cleaner and it doesn't get hot any more. My first thought was that the problem was arcing causing a wire to overheat etc. But- if a wire overheated and shorted wouldn't the fuse just blow again? So- before digging into the fuse panel I checked the ignition switch and found that the "start" terminal reads 7 volts? Shouldn't this be 0 until it's energized? I'm thinking there's either a short on the wire to the starter relay or the relay has an internal short? Is my reasoning here sound? Any other ideas what it might be? Any suggestions are appreciated. . Thanks

 

[BrianCinNC]

Btw- the start terminal reads 7v when the key is in the off or run position.

 

[Tazza]

Btw- the start terminal reads 7v when the key is in the off or run position.

It kinda does sound like another wire is shorting or partially shorting to give 7v there. The fuse shouldn't have gotten hot, glad contact cleaner fixed that, but it's possible the bad connection melted the wires behind it? or have you already checked that?