Rusty Bobcat S650 electrical problems, starts then shuts down

[jettech]

I’m helping out at the farm and there’s a rusty S650 that used to be used for snow removal. There’s more rust than white paint. I’m a mechanic but I know nothing about these machines. It has the operators manual behind the seat, found the fuse box, all of the fuses were good. The main relay box fuses were covered in dielectric grease, probably a hint this has had problems before.

The left side doesn’t turn on at all, gauges, lights, switches, or climate control. The right screen turns on with the bobcat logo and fades all white. Cranks and starts good, runs for a few seconds and shuts off.

I checked the battery grounds…rust. Cleaned everything back there. Then it wouldn’t do anything at all. How does cleaning grounds make it worse? Then I cleaned the positive post and the 100A master fuse, also rust. Back to square one, runs and shuts off, no left side electrical, screen turns all white.

How do I get behind the fuse box? I’m thinking the power wires in the are corroded behind it. Is there any chassis grounds in the cab area? These bobcats don’t look mechanic friendly to get to things. Thanks in advance!

 

[Simon C]

Just wanted to say that if you look up Die-Electric grease you will find out it is a non-conductor and there is even some videos that demonstrate that fact. Good stuff for the outside of connectors to prevent corrosion from getting in, but any loose spade type connectors with that on it is only a recipe for failure.
One ambitious gent did all the plug ins he could find on his vehicle, only to find out he had a no start after it. Brought to dealership a guy I know was working at and a full day to wash all that stuff out. They said they like those kind of jobs.
Do some voltage drop tests of frame, engine block Cab and computer grounds back to battery Negative to see how much loss you have. Never trust a battery cable by how it looks.
Simon C

 

[jettech]

I spent some time cleaning all the dielectric grease out of the fuse box. Also got the box to drop out so I could see behind it, wiring looks perfect. But there’s no big red power wire like I was expecting, only a few smaller gauge red wires and a bunch of orange. Only change is the screen flickers with a better image of the bobcat logo before fading white again. Definitely on to a voltage drop somewhere. So now I want to find where the big red cable goes from the battery, there must be a post or buss of some sort for the smaller wires for the fuses, I bet that is corroded. I think I need to get under the seat but it looks like the whole thing is held down by the cab, of course those bolts are crazy rusty and probably are going to be a fight.

 

[Sbrant]

I spent some time cleaning all the dielectric grease out of the fuse box. Also got the box to drop out so I could see behind it, wiring looks perfect. But there’s no big red power wire like I was expecting, only a few smaller gauge red wires and a bunch of orange. Only change is the screen flickers with a better image of the bobcat logo before fading white again. Definitely on to a voltage drop somewhere. So now I want to find where the big red cable goes from the battery, there must be a post or buss of some sort for the smaller wires for the fuses, I bet that is corroded. I think I need to get under the seat but it looks like the whole thing is held down by the cab, of course those bolts are crazy rusty and probably are going to be a fight.

More than likely the positive cable from the battery will lead to the starter. Then you’ll see a smaller power wire leading from the starter up to either a connection point or to the fuse panel. That’s why you’re only seeing smaller gauge power wire off the fuse panel.

 

[jettech]

Finally got this running, after taking way too much apart tracing wires, it ended up to be simply just a bad relay. Switched power relay was bad. Started swapping relays around and certain things started working/not working, narrowed down to one generic looking auto relay. The rusty bucket of bolts lives on!

 

[Simon C]

I built breakout cables to be able to test the relays with them in your hand and meter leads on them as they are actuated to see if they really work.
Simon C