I have a CAT 277 that the 10 amp fuse will blew after about 4 mins of running. At first i was warming the machine up and it cut off on me after coupple of minutes running. Then it would only run while the key was in the starting position let go of the key machine would stop. I swapped relays and replaced fuse nothing different. I used voltmeter and on green wire key on have 12v, pink wire has aprox 9v while cranking then drops voltage when key is in the run postion. I hooked 12 volts to pink wire on solenoid to unload the machine off my trailer to get to the shop. I installed a new fuel shut down relay and new fuse and cranked and started like it should, machine runs then the dies like before. Rechecked the 10 amp fuse and blown again. I know from the schematic that the green wire goes from the A terminal all the way to power side of the 10amp fuse that blows. The other side of the 10amp fuse goes to a main power relay. Is it in the solenoid i am going to order one to try to test. I am guessing that the coils are not operating right and when it gets warm it creates too much resistance maybe. I will test tonight with spoons and two meters while running with one probe on green wire and one on the pink wire to see if voltages change or just check voltage at the fuse to see how much voltage it is getting before it blows. Thanks
Believe it or not we ran into the same problem on one of my 277's if I remember right we eliminated the possibility of harness chafing (make sure you do that first) and then replaced the key switch because it was a little loose and faulty anyways and a shut off solonoid I think we ended up just running a 15 or 20 amp fuse in it......it's nearly a straight shot from the fuse panel through a relay then onto the solonoid with a decent wire so nothing to damage there if it's kept under 20 amp because it's probably not pulling 20a the entire time its more than likely just a spike once in a while not sure why...... Edit, come to think of it, if it's a amp spike popping the fuses I would be curious if they make "slow blow" blade fuses ? Just looked at some charts, and at 5' on 12v a 14ga wire is good for 50amp and 18ga is good for 24amp The way I look at it is if the solonoid is faulty and shorting out the hell with it feed it with enough amperage it smokes it and shows itself..... Hell it's bad anyway what's it matter ? If that is the case and I'm sure you can always ziptie or wire the kill rack mechanism on it so you can get on a trailer Second edit, I talked to my hand and he said that he dont remember for sure but thinks that the heavier fuse cured the problem Pj
Do you have an amp-meter you can install inline with the shut down solenoid? Check draw there then work back one point at a time in the system till you find what is causing the draw. If the shut down solenoid is controlled by a relay. The relay or the wiring from the switch to the relay would be where I would expect to find the fault. If I had the complete S/N I might be able to pull up the wiring diagram to have a better idea of where to look.