Technician requires some insight ( Energized frame w/ batts off )

[TEX32]

Afternoon fellas. Licensed tech here ( 20 years ) Need a hand trying to figure this one out...

Details: Cat 980G. 4 batteries, 2+2 set up, 24 volt system. ( obviously )

- When batteries ON, frame is grounded 100%
- When batteries are shut off, frame energizes to 95% source voltage. ( 25.6 source voltage, frame energizes to 22.5 v )
- All battery positive ( + ) cables are secure with zero `rub through` along frame &/or P-clamp locations.
- Starter NOT shorted
- Alternator NOT shorted
- Positive junction block NOT shorted
- Ignition switch NOT shorted
- Injection pump shut off relay de-energized

- When hood actuator harness disconnected from positive junction block post, frame energization drops to 11 volts.
- Harness NOT rubbed through

Ideas, thoughts... ?

 

[Cmark]

So to get this straight, with the master switch off you are putting a DMM between battery negative and the frame, correct? If that's the case then it's to be expected. Voltage will feed back through any closed circuit, bulb, relay etc.

 

[TEX32]

Cmark: The frame of the unit becomes energized. When utilizing a PowerProbe ( fancy test light ) I can pull over 22 (+) volts from the frame, body, engine, etc... and when I supply a ground to the frame I can get amperage ( essentially short circuiting )

 

[Vetech63]

My question is, what was the original problem that led you to this point?

 

[JPV]

Cmark is right, your power probe will show voltage but if you tried to use that voltage to light a test light it won't. I ran into the same thing, had me scratching my head until I figured out my tool was smarter than me! I had never noticed they did that before I had a power probe that makes it so easy to check everything.

 

[John C.]

Where are you checking for voltage at? Are you going from the frame to the negative post on the battery?

 

[TEX32]

Vetech63: I am currently installing `battery shut off indicator lights` to notify operators that they have left their batteries on. It is an small button type LED mounted by the steps as a visual cue. Wired to a constant, non-keyed voltage source and frame ground. I noticed that the LED only dims out, when batteries are shut off. This got the ball rolling. However, an incandescent light will extinguish. ( P.S. none of my other units do this with LED`s installed )

JPV: The frame will illuminate a LED @ 6 volts. When there is NO LOAD I am measuring 22v @ frame. When loaded, via an LED, the frame drops to 6v.

John C. : Power Probe hooked up to batteries ( 24v pos & Neg terminal ) I read 22v on frame.

 

[Nige]

If an incandescent light in the same circuit will extinguish then I recall when a large number of lights (incl. the red/green payload indicators) were "upgraded" from incandescent to LED on Cat haul trucks it caused all sorts of weird behaviour in electrical/electronic systems. Memory is a bit fuzzy as regards the detail though.

 

[JPV]

I see, I didn't realize it would light an led, I think it is normal but a little weird, like I say I have noticed the same thing but not until I owned a power probe.

 

[Cmark]

There must be something allowing current between battery neg and ground. If you disconnect the batt neg cable at the back of the master switch what happens? Try disconnecting each battery in turn. An LED only needs milliamps to light so, for example, corrosion between a battery post and battery hold down clamp can pass enough current.
(I assume you've checked for something wired directly to batt neg; aftermarket lube system, radio memory, payload indicator, etc?)

 

[Vetech63]

It looks like your in good hands here. I know people that have tried multiple ways to indicate master switch turn off...….if its a light, they don't see it...….if its an alarm, they don't hear it...….if its fart spray, they don't smell it. The only way I KNOW it would work is if you could rig up something that would gut punch them when they climb out of the cab.

 

[John C.]

The master switch thing isn't hard at all. Dead batteries once from switch being left on and you get a verbal warning, left on twice you get a written reprimand and a warning that the next instance might be your last at this company. Third time is a charm. You can tie that in with running out of fuel, not checking fluids and not greasing the machine.

 

[kshansen]

The master switch thing isn't hard at all. Dead batteries once from switch being left on and you get a verbal warning, left on twice you get a written reprimand and a warning that the next instance might be your last at this company. Third time is a charm. You can tie that in with running out of fuel, not checking fluids and not greasing the machine.

Now if this was one of the older machines with the battery disconnect right next to the seat I'd suggest putting the disconnect key on a leash around the operators neck

 

[TEX32]

You guys are awesome. Not a single one of our operators do these things. Same story across the whole world, I guess.
Had an issue with guys not checking fluids, etc... so I went in to work at 4 am, removed every single key from the machines and zip tied them to the dipsticks. Sat back, and waited... Not a single operator found a key! However, I recieved 13 calls that "Someone had stolen all the keys" HAHAHAHAH ! IT WAS AWESOME. But disconcerting at the same time...

 

[TEX32]

Cmark: I regards to your last post. I have exhausted all of those suggestions before seeking online help. We think alike.

 

[tractormech]

Not familiar with your machine but....does it have a solenoid like a komatsu that,when energized,fires up the electrical to the rest of the tractor? There will be a hot wire to energize it,hooked up to switched power,possibly through the key switch because all other electrical is dead at this time. Maybe the solenoid is shorted internally to the frame or the wire to energize it is rubbed and shorting.A schematic would be awesome to let you know what goes where. Gotta love electrical problems....10 hours to find and 10 minutes to fix.

 

[TEX32]

Tractormech:
We have Komatsu's as well ( 250's, a 320 and a couple 500's ) I do know the solenoid you speak of and our 980G doesnt have one.

 

[heymccall]

I'd like to see what happens when the "product link" fuse is removed.

 

[kith]

Some of the newer machines have a small wire like 16 g that hooks to a separate small post on the master switch. This wire is for the keep alive circuits in the various controllers and is always energized.

 

[heymccall]

Had an issue with guys not checking fluids, etc... so I went in to work at 4 am, removed every single key from the machines and zip tied them to the dipsticks. Sat back, and waited... Not a single operator found a key! However, I recieved 13 calls that "Someone had stolen all the keys" HAHAHAHAH ! IT WAS AWESOME. But disconcerting at the same time...

I nearly got fired for something similar.
We started a new jobsite and I checked each machine as they came off the lowboy (10pcs). Put 10 unit numbers in a hat, and picked one. Taped a $20 bill to the engine oil dipstick on a Caterpillar 330CL. Had other obligations and didn't return to that site for three weeks.
It was an overcast day, light breeze, I'm guessing mid September, about 1pm, and as I drive in, I see the Cat 330 at work.
Tell the operator that I had to get something from under the engine hood. He idles down, I climb up top. As I'm removing the dipstick, a curious operator watches from inside the cab. I nonchalantly unfurl a $20, all the while avoiding any more eye contact. I close the hood, climb down, get in my truck and proceed to the other side of the jobsite.
I heard absolutely zero chatter on the 2way radios or the CB, but, it took 11 minutes for the owner to ring my phone.

Turns out that they were test demoing a new excavator operator that day. To his credit, he did work until end of shift. Was never told if he quit, or was released for underperforming as a ditch digger.