hello i need some help with a old 966c the operator was running it when all of a sudden, the starter started spinning over. they pulled the fuel pedal to shut the loader off and the starter was still going so they turned the battery disconnect off and it was still spinning. it finally stopped when they jumped out and disconnected the wires to the starter. so i figured the solenoid on the starter shorted out and grabbed a new starter installed it and now every time you turn the hot start switch to start it kicks the 40 amp breaker, the glow plug side works fine thou or at least the ammeter drops a little to the negative side when you have the switch held im assuming thats normal?. So I lifted the dash up (not much room under there Hehe) and began inspecting wiring etc. i finally figured i would bypass everything and took the signal wire off the hot start switch and disconnected the side of the 40 amp breaker that goes to the ammeter and touch the 2 together and still it kicks the breaker so then i figured maybe theres a bad wire so ran 2 new wires and still it kicks the breaker. so tomorrow i am going to do all new battery cables the old ones have seen better days. any help or ideas i could get would be amazing oh and the batterys had 12.5 and 12.4 readings thankyou. the breaker is a new cat one so i wouldnt think it would be weak but of course new doesnt mean good.
Welcome to the Forums MM. Glad to have you. I closed the other thread in General Industry questions on the same topic so all replies can be directed to this thread. Best of luck.
thankyou i was not sure which one i would have the best chance to get a answer in
No worries.
A Serial Number might get you an electrical schematic, but often with these old girls it's a case of pot luck. Back in the day the wiring was often included in the Parts pages. The one thing you do have going for you is that the electrical system on them is not very complex at all.
You will probably need a good DC clamp on meter to test how many amps are actually going through the breaker and any suspect wires. Cannot tell if a breaker is faulty without a clamp on. Yes as Nige said there is not many wires on these units. The fact that the starter stayed engaged and ran all kinds of amps through the wires and cables means you will have to test all the switches under load to see who is messed up. Simon C
I think I would start at master switch. If you remove the ground to batteries starter should stop. I would also remove ground cable from battery and check voltage between frame and positive terminal,I've seen batteries make ground thru case when they were packed with mud and coal
hello Nige, i have ready many many helpful comments from you. the serial is 76j-4003 and i do have the diagram out of the parts manual the machine was last fully rewired in 2006. and yes they are not complicated at all this old iron is some of the best. I bet the old timers that built them sure didn't think people would be running them still to this day. hello, Simon, a clamp meter is a good idea i just might have to invest in one. the weird thing is that i only have the 2 wires for the starting circuit connected to the breaker and it still trips it hello, Pittsburgh, yes i did disconnect the negatives of the master and cleaned them together with vise grips but it still tripped the breaker i am going to replace all battery cables tomorrow with some fresh 2/0 welding cable
I am thinking I got a bad starter if I put my meter on continuity and put one probe in the signal hole and the other on the engine block it beeps
First thing I see is that your master disconnect switch is not actually disconnecting or it should have stopped the starter spinning when switched off You should have continuity from the signal terminal to ground. That is normal. It gets its continuity through the solenoid windings. Can you leave the signal wire off and test the wires continuity to ground. Also could try a push button starter signal or jumper to see if the starter works.
Thankyou guys for the help but unfortunately it was purely human error on my part and didn't realize there was a cover hiding the signal wire stud so the whole time I was grounding out the solenoid it took me calling cat and telling them the 2nd starter I got from them was junk too until the most competent parts guy I've ever met was like hey you gotta take the cover off. I said I don't feel as bad the cat mechanic who tested it didn't know that either lol what a happy humbling experience. The loader got a good looking at the wiring and some new battery cables out of the deal though.