Electrical wiring

[DDlighttruck]

(01-11-2020 )Waterloo Wrote:  

(01-11-2020 )DDlighttruck Wrote:  

(01-10-2020 )Waterloo Wrote:  Depending on the age of the truck, mine is ten, and I have seriously thought about purchasing a new engine harness. Those wires eventually go green, and there will come a time when these harnesses are no longer available...

I had a lot of whacky issues with gauges last year, it all pointed to no communication from the ECM to the truck. Truck ran fine, drove fine, but at least 8 gauges like speedo and tach were dead. Changed the engine harness myself, about $1400, fixed everything.

The OP said he’s not having issues, but for me my harness was probably 15 years old and I felt that was a smarter way to go.

If the truck is a keeper, being proactive and purchasing a new harness while they are still readily available is a smart thing to do in my book, because eventually these harnesses do get old, brittle and green. When that day comes, and you realize it is time, only to find out that they are no longer available... Then what do you do? Then you have a real mess on your hands. I would purchase now, and at least have it in reserve, because that day will eventually get here, especially if you run up north.

Agreed. I may look into the Cummins side of things to change that one out, too

On newer trucks where sensors are reading milliamps I would think that the harness and plugs is even more crucial to having them run right

[RocketScott]

High temp split loom holds up better than the harbor freight stuff:

https://www.delcity.net/store/High!Temp-...m/p_811350

There are also wrapping tapes specifically made for harness bundling but I haven't used them. The Chinese finger trap stuff works ok but takes some planning and effort to get on, pretty much have to rebuilt the harness. If you can route the wires away or shield them from hot parts it will help quite a bit

Even though I could have bought them I made my engine harness and headlight harnesses from scratch. Way cheaper but takes time and a little bit of skill. Need to invest in a few tools to crimp and assemble/disassemble too. All the connectors are off the shelf stuff and components can be ordered from several places. In many cases the connector housing can be reused. I have an old truck so all the wires are numbered with tags, not color coded. Three spools of white, black, and red wire were all I needed. If you wanted to keep the wires color coded it would get a lot more expensive

I'm not sure how the newer trucks are but the '89 379 had several extra circuits for features my engine doesn't have, the wiring for jakes was an add on harness, and on my truck the crane wiring was hacked into the engine harness for a start/stop switch. The new harness I made only has what it needs and the jake and crane wiring is integrated. Sure cleaned things up and makes it easier to work on

[JimT]

Ok, thanks for all the replies!

Let me touch on a few.

Yes I am having electrical issues of an unknown origin. Part of the reason I've embarked on this journey. I touched on that in a different thread and don't have anything new to add, so far. So I'm working my way through all the wiring from the batteries on out.

The reason I questioned harness replacement over repair is the brittle/crumbling nature of the split loom. It's literally falling apart when I touch it in some places. This makes me question the condition of the wires inside. There was also an incident when I first got the truck where both rear motor mounts broke and the engine shifted. It's a story for another thread (and a lesson I won't forget), but it does leave me with a concern that a wire might have been pinched or stretched and noone noticed. (Not likely given the routing, but not something I can just shrug off either)

All the connectors to sensors on the engine that I have inspected so far have been clean and free of corrosion. However some of the wiring for lights and the main cables going to the battery, starter and alternator all showed signs of heavy corrosion. That's what prompted me to replace them. I chose to use 4/0 for reduced resistance, higher durability and increased capacity (future proofing). I have been using http://www.batterycablesusa.com for a while now. Very high quality cable and workmanship. They sell through amazon too, but at a higher price then direct.

RocketScott: Thanks for that link! The best I'd found so far was good up to 200F. With the proximity to the exhaust/EGR pipes I was a little concerned that 200F wouldn't be good enough.

Rawze: I thought about using flex-seal but the flammability warnings on the label gave me pause. I saw your recommendation in another thread for CRC 06026 Heavy Duty Corrosion Inhibitor and ordered some. Figure I'll try that out on the bare battery, starter and alternator connections. Will probably clean and then paint over the ground connections on the frame as suggested by JMBT.

JMBT: Thanks for the info. I had pieced that together from other threads but it's good to have here for easy reference.

I'll be starting a 'your daily blog' thread soon to chronicle my learning experiences and go in depth with truck details and issues. Hopefully the generic info in this thread can also be useful to others in the future.

More suggestions? Recommended products? Links to existing threads? Add them here!

Thanks again.

[Chamberpains]

Ooo ooo do tell how 2 engine mounts get broke. That quite impressive. I love a good "holy, what the fu'x just happened" story.

[JimT]

(01-11-2020 )Chamberpains Wrote:  Ooo ooo do tell how 2 engine mounts get broke. That quite impressive. I love a good "holy, what the fu'x just happened" story.

I had to open my mouth... :too_sad:

You can find my epic tale here http://rawze.com/forums/showthread.php?t...5#pid48875