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Master Switch

CANNONMAN1

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Joined
Oct 18, 2009
Messages
60
Location
Portage, WI
Well, dodged a bullet a few nights ago. One of my trucks started on fire in the shop. Dogs woke me and I was able to drag it out with minimal damage to shop but truck is gone. I’m putting Master Cutoff Switches on everything I own. It could have been disaster! Bought a few switches, and they differ as to either putting switch in positive or ground cable. What cable is best to install switch in??
 

CANNONMAN1

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Joined
Oct 18, 2009
Messages
60
Location
Portage, WI
In doing the ground cable, which it looks like on most of my heavy equipment, would you not have power still running directly to the starter which is then grounded where it’s bolted to the block?
 

DB2

Senior Member
Joined
Jan 4, 2015
Messages
1,008
Location
Winnipeg MB Canada
But because the ground cable is disconnected by virtue of the switch, the negative side of the battery isn’t completing the circuit.
 

John C.

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Jun 11, 2007
Messages
12,865
Location
Northwest
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Machinery & Equipment Appraiser
What kind of truck and any details of which component the fire started in? It might be something we should all look for.
 
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CANNONMAN1

Well-Known Member
Joined
Oct 18, 2009
Messages
60
Location
Portage, WI
The truck was a ‘96 Chev. 2500. Not a typical ‘96. it was very sharp, with only 83,000 miles. It had been parked in shop for 2 1/2 days prior to starting on fire. Shop is nice & clean, but we get the occasional mouse. Thinking that may have been the culprit. Who knows.
 

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CANNONMAN1

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Joined
Oct 18, 2009
Messages
60
Location
Portage, WI
Me too! It could have been utterly disastrous. The shop is 20,000 sq. ft. Full of equipment, classic cars, boats & such. Dogs got Ice Cream a lot the next day. The shop is 80’ from the house. I never would of heard a thing until it would’ve been to late I’m sure. As it is only dash area was burning when I got to the door. Yanked it out with a tractor that was right in front if it. Not without some injury! Everything in the shop right down to lawnmower is disconnected now. It looks like general concensus is to switch negative cable. Starting on that tomorrow.
 

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Truck Shop

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Joined
Dec 7, 2015
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Location
WWW.
From what I've experienced through the years a high percentage of vehicle fires that start out of the blue, the bulk head connection or
power distribution box is usually in the mix if wiring has not been tampered with. PacCar [KW & Pete] both have their issues in that area.
Normally start by moisture corroding/rotting connections creating resistance.

Ever notice on some occasions when stripping the insulation back on a white ground wire the copper is blackened instead of shinny copper?
 

CANNONMAN1

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Joined
Oct 18, 2009
Messages
60
Location
Portage, WI
Truck Shop, that’s interesting as the reason we moved it into shop was a huge storm on Fri. night. Rained like crazy and the left window had been left down. The seat was wet and we were expecting more storms all weekend so we put it inside to dry out. Never thought it was that wet, but now you have me thinking.
 

emmett518

Senior Member
Joined
Mar 24, 2021
Messages
810
Location
USA
The wiring diagram from Deere for my 310 L put the switch on the + side. The boat I used to own switched +. Although your logic and reasoning for putting it on the negative side makes sense.
 

John C.

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Jun 11, 2007
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Northwest
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Machinery & Equipment Appraiser
Many older systems before the installation of micro processors put the master switch on the positive side. There were no shut down motors and engine throttle controllers on those machines. Cat has been consistent with putting theirs on the negative side. It seems that now days all the manufacturers put it on the negative side. On the Komatsu side, there is a reason for it.
 

JLarson

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Joined
Aug 23, 2020
Messages
656
Location
AZ
Occupation
Owner- civil and heavy repair/fab company
Yikes, rough burns, def need to keep those clean and covered.

The top places we see electricals start is same a truck shop, the PD box and connectors, also alternator harnesses are another big one on vocational trucks it seems like. And any Paccar product, their electrical is like a fucking spaghetti mess, those things light up anywhere, engine harness, over the batts, under dash,,, especially if they have been "upfit" then you just have a ton more spaghetti.
 

emmett518

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Joined
Mar 24, 2021
Messages
810
Location
USA
Many older systems before the installation of micro processors put the master switch on the positive side. There were no shut down motors and engine throttle controllers on those machines. Cat has been consistent with putting theirs on the negative side. It seems that now days all the manufacturers put it on the negative side. On the Komatsu side, there is a reason for it.

The Deere manual reminds that you need to give the machine ten minutes after shutdown before you turn off the power switch to allow the DEF system to purge out the lines to avoid freezing.
 

Coaldust

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May 9, 2011
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3,286
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North of the 60
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Cargo Tanks, ULSD, RUG, Methanol, LPG
Same with trucks. It’s hard to get the drivers to wait long enough to purge the lines. They like to bail out of the cab as soon as they can. It’s almost not worth it to have drivers use the disconnect switches. Services like Qualcomm, Peoplenet, and Smartlogix do updates in the evening and the switches have to be on. Now, you have software issues.

My neighbor just burnt down his well drilling pipe truck due to an after-hour electrical short. Could have been prevented with use of the disconnect switch. Right when I hired him to drill me a well. My luck. Been waiting all summer for well casing. Holy cow! Pipe got expensive.
 
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