hello to all. I am working on a komatsu pc100-6 that will not start. it has been sitting for 2 1/2 years and it ran when it was put away. it has new batteries and when you go to the crank position of the key all power goes away {like a major voltage drop**. where the battery positive cable hooks up there is a unit I don't know what it is. 25volts goes in. there are 2 smaller connections with white wires going to it and a bigger connection that feeds the starter. when I put the key in the crank position it goes from 0volts to 2.5volts. I pulled the cover off this and it is rusted inside. first of all what is this and am I safe to say that my issues with loss of power at the console may be due to this part. most of why am asking for help is that I have no trouble shooting charts or books for this excavator
You need a voltmeter and an assistant. Have the assistant try cranking it while you check voltage, starting at the first battery. You can have a bad connection anywhere along the way that shows voltage with no load, but put a load on and voltage drops to zero.
That's a battery disconnect relay. These Japanese machines almost always have them, there's only power to the key switch and nothing else until you turn the key. If you want to get it running temporarily just move the big cable from the starter over and put it on the other big terminal where you have 25V. Please disconnect the ground from the batteries before doing so. Whenever you shut the machine off you should disconnect the battery ground, until you replace that big battery relay. Usually around a hundred bucks from your dealer.
thank you for your help. from the time I posted I was wondering around google and got a pic of this unit and saw it was called a battery relay. so you are saying probably all the rust inside is probably causing my voltage drop to 2.5volts at the big terminal lug to the starter, and if this is true then the monitor loosing power in the crank position is probably related. since you know this then can you help me decode the machine serial # to know what I got {year that is**