Electrical issues.
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Mountain Pass
Joined: Jan 2016
Posts: 248
Likes: 1
Electrical issues.
So guy's I'm about 3 quarters of the way through this Cummins swap on my 03 6.0. So the other day I hooked up my batteries to start it for the first time. Keep in mind I had to crank a few times to get the fuel up to the motor. at that time I noticed my lights were working normally so the next day I went out to work on the truck and opened the door to get something and all my lights were flickering on and off really fast you could here the blinker relay for my turn signals going nuts. I have an engine ground, chassis ground but no cab ground yet (not sure if that would cause strange behavior like that or not) I have not modified my wiring in anyway. My wiring harness is not connected because it's being modified by diesel conversion specialists to match the 12v Cummins. Anyone know what could be causing this issue. batteries could be weak because the truck hasn't been ran since September but I've had weak batteries in the past and never caused anything like this. Does anyone know what could be going on hear? I have alot on my plate at this point and don't need this thrown into the mix. Please help. Thanks.
Hotshot
Joined: Dec 2014
Posts: 17,830
Likes: 3,115
From: Jersey Shore
The cab shell is the ground plane for all electronics. There are 3 connections in a stock condition. An 8ga main lead from the passenger battery negative terminal to the fender. However, that does not match the 4ga positive lead from the driver's positive post to the central junction box. To get to parity, there is a 12ga bonding strap under the passenger footwell to the frame, and then there is a 12ga bonding cable from the back of the engine to the firewall above the heater blower. All three of those work in harmony once the engine is running. Not so much when the starter is engaged, the 12ga flow in the opposite direction and stress the 8ga, more so if you put a ground strap from the engine to the fender.
The frame of the truck is just a bus bar between the engine and batteries, and for the back of truck connections of lights and trailer connections. And the 12ga bonding strap under the cab.
The frame of the truck is just a bus bar between the engine and batteries, and for the back of truck connections of lights and trailer connections. And the 12ga bonding strap under the cab.
Thread Starter
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Mountain Pass
Joined: Jan 2016
Posts: 248
Likes: 1
The cab shell is the ground plane for all electronics. There are 3 connections in a stock condition. An 8ga main lead from the passenger battery negative terminal to the fender. However, that does not match the 4ga positive lead from the driver's positive post to the central junction box. To get to parity, there is a 12ga bonding strap under the passenger footwell to the frame, and then there is a 12ga bonding cable from the back of the engine to the firewall above the heater blower. All three of those work in harmony once the engine is running. Not so much when the starter is engaged, the 12ga flow in the opposite direction and stress the 8ga, more so if you put a ground strap from the engine to the fender.
The frame of the truck is just a bus bar between the engine and batteries, and for the back of truck connections of lights and trailer connections. And the 12ga bonding strap under the cab.
The frame of the truck is just a bus bar between the engine and batteries, and for the back of truck connections of lights and trailer connections. And the 12ga bonding strap under the cab.
Thread Starter
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Mountain Pass
Joined: Jan 2016
Posts: 248
Likes: 1
yes no cab ground from the passenger side battery ground cable to the cab and I forgot to hook up the strap from the cab to the back of the block also. I didn't realize until you mentioned it.
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Mountain Pass
Joined: Jan 2016
Posts: 248
Likes: 1
If it should be broken could I just use regular black automotive wire to make a new one? I mean just as long as it's a heavier gauge. The strap that mounts to the fire wall more than likely is going to be to short to reach a spot on the block to ground it so I may need a longer/custom ground strap. That's why I asked about making it.
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Hotshot
Joined: Dec 2014
Posts: 17,830
Likes: 3,115
From: Jersey Shore
Sure you can, I did. But I'd try to keep those two at 12ga. Stock, you have an 8ga off the passenger battery, I added another 8ga off the driver's battery to that fender.
But this is talking about a layout for the 6.0, with the Cummins you are wide open what to do. But there has to be some negative side connection to the frame to supply the rear of the truck lights and trailer.
Ford and other companies use the braided cables for flexibility, but normal wire can be used, it just needs a loop in it.
But this is talking about a layout for the 6.0, with the Cummins you are wide open what to do. But there has to be some negative side connection to the frame to supply the rear of the truck lights and trailer.
Ford and other companies use the braided cables for flexibility, but normal wire can be used, it just needs a loop in it.
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Thread Starter
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Mountain Pass
Joined: Jan 2016
Posts: 248
Likes: 1
Sure you can, I did. But I'd try to keep those two at 12ga. Stock, you have an 8ga off the passenger battery, I added another 8ga off the driver's battery to that fender.
But this is talking about a layout for the 6.0, with the Cummins you are wide open what to do. But there has to be some negative side connection to the frame to supply the rear of the truck lights and trailer.
Ford and other companies use the braided cables for flexibility, but normal wire can be used, it just needs a loop in it.
But this is talking about a layout for the 6.0, with the Cummins you are wide open what to do. But there has to be some negative side connection to the frame to supply the rear of the truck lights and trailer.
Ford and other companies use the braided cables for flexibility, but normal wire can be used, it just needs a loop in it.
Fleet Mechanic
Joined: Feb 2007
Posts: 1,652
Likes: 79
From: Mooresville, NC
Run Voltage Drop tests on the Ground Side.....start at the Battery with Digital Multi Meter (DMM) on DC Volts
Connect + Side of the DMM to Body Ground and the - Side of the DMM to the - Battery Post..........note Voltage Drop
then work backwards thru the vehicle chassis.........same setup
You can also accomplish the same with a Power Probe connected to the battery if you happen to have one...............very handy and will light up red (voltage) or green (ground) downstream anywhere along the chassis
Connect + Side of the DMM to Body Ground and the - Side of the DMM to the - Battery Post..........note Voltage Drop
then work backwards thru the vehicle chassis.........same setup
You can also accomplish the same with a Power Probe connected to the battery if you happen to have one...............very handy and will light up red (voltage) or green (ground) downstream anywhere along the chassis
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