Lately one of the things I've been working on fixing on my 1994 Cat D4H is wiring problems and different electrical problems to try to get things like trouble lights, gauges, horn, and the backup alarm working properly. I'm OCD about just wanting things to work like they should. Anyway I've found that on my machine in addition to places where the wiring has been damaged by physical damage (sometimes repeatedly by the number of previous repairs) there are a number of places where the insulation on the wiring has completely disintegrated leaving the copper wire conductors completely uninsulated. Usually this occurs at the ends of the wires where the wires terminate at a connection of some sort and the insulated wires actually leave the outer wiring harness covering. The other thing I've found on my machine is that some of the rubber covered harness connections ( this machine was prior to the more modern molded harness connectors) have obviously leaked over the years allowing corrosion inside of the connectors. Some of the connectors were corroded to the point that the pins and sockets are no longed conductive. Some day when I have a bunch of free time, I have a slew of electrical problems to sort out with my Cat backhoe as well. The whole point of my post is I was reading a couple of other recent posts on HEF and it occurred to me how often wiring harness problems occur in heavy equipment. Whether it's due to wires shorting to each other inside of the harness, shorting to ground by wearing through the outer harness and the wire insulation, or water problems in the connectors or in the harness causing intermittent voltage leaks, ect. I'm not a heavy equipment mechanic, but I'm sure that the number of wiring related problems has only increased with the increase of computer controlled equipment, more and more harnesses, and more and more sensors. I'm curious if those of you who have worked on or owned various brands of equipment find that some brands are better or worse than others. It surprises me that the insulation Cat chose to use on my dozer has not really held up very well over the years as well as I would think it should have. Some will say I'm being unreasonable since my machine will have its' 30th birthday next year. If you think about it though, if the wiring in your attic began breaking down and the insulation disintegrated causing your house to burn down after just 30 years that would be ridiculous. Having been an electrician in a previous life I have an appreciation for the properties of the insulation on wiring conductors, and know there are conductors available that are made to withstand oil/chemical exposures, as well as temperature extremes. I'm not trying to bang on Cat, I like the machines I have, I just started thinking about the wiring the manufacturers use after working on my dozer this weekend and reading some recent posts.
I don’t think that you can compare domestic or any other type of fixed wiring with machine wiring that is subjected to extremes of temperature, vibration, impact, contamination with petroleum-based products, coolant, etc.
I'm not comparing the two, clearly they are apples and oranges, however there are thermoplastic wiring insulations available that can and do withstand all of the extremes you listed without dissolving in less than 30 years. There are cars and trucks out there from the 1950's and 60's that don't have their wiring harnesses falling apart as bad as heavy equipment half their age. It just seems to me that with as many problems as you see and hear about with wiring on these quarter and half million dollar machines, that the manufacturers don't do a great job of installing trouble free wiring systems in them. That's why I posted the topic in the first place, to see if one or more of the manufacturers was better in that area than another. Often times there is knowledge that people inside of an industry have that others just looking in from the outside don't have.
My biggest complaint with OEM harness mfrs is some use peanut or soy based lubricant during assembly. That just draws vermin from everywhere for a free buffet. Beyond that I can say from experience Volvo has notoriously fragile harnesses in their older excavators. It seems to be a supply chain thing. I have seen older harness insulation flake and disintegrate as you described. Yes always at the terminal and working back. I believe this is caused by the terminal itself getting a weaker hold on its mate over time. As the friction connection gets worse, the heat increases which would accelerate the process. By contrast, we've had in-engine harness bathed in oil subject to extreme heat and vibration that seemingly lasts forever. I'm sure it all comes down to dollars and cents. How cheaply can we build it to satisfy the warranty period?
As far as I'm concerned heavy machinery wiring harnesses are simply another component to be replaced when the machine is overhauled. The wiring could be considered to "wear out" in just the same way as an engine, a transmission, or any other machine component. In my experience a large percentage of wiring problems are often the result of a failure on the part of the mechanics to correctly replace zip ties, harness clips, etc, etc, during a repair. That's Lawns & Gardens size equipment. Try $3-5m a copy..........
Another anomaly, it seems is data speed. They're jamming so much data through the many CANs and databus at such high speeds that they aren't adequately shielding the resulting RFI from neighboring circuitry. I was recently assigned a shiny new Navistar MV service truck. It promptly threw errors for air conditioning. It's been at the dealer and they've been working hand in hand with International corp. The solution, as recommended is to acquire and install an overlay harness for just that circuit. I've encountered this as a "solution" for other mfrs as well. As a dealer tech, I never would have accepted this as a "solution" It seems commonplace now. Here we are, modern technology and all that running jumper wires like a bunch of shade-trees. Shameful!
$3-$5 million a copy holy crap, that's even worse. I agree with you about the replacement during overhaul. I also agree about failing to replace securement devices when working on something. I think you're right on the money. I'm sure price competitiveness plays a role in it as well.
On that size of a machine it would be put through a PCR (Planned Component Replacement) programme approximately every 20k operating hours. At that time all the wiring harnesses would be replaced along with all the components. This would be every 36-42 months on a 24/7 operation. The cost of the harnesses would be nothing compared to the cost of the replacement components.
Nige I've had more than one person tell me that a number of companies that have the ability to do it in house prefer to buy older pre-emissions, pre-computer machines and spend the money to totally refurb them in their own shops in lieu of buying new machines. Do you encounter the same thing on your side of the pond?
No. The outfits I worked for always bought brand-new and upgraded diagnostic capabilities in the maintenance department as newer more complex generations of electronics came in. Even a total fleet value in excess of $100m was considered small, and there were some fleets around whose value was 10 figures.
The plastic weave that appears to have been shrunk around the wires on my 86 Champion grader seems to be very durable. The insulation on the wires is pretty thick too but it isn't fine strand wire at least on the articulation wiring for the solenoids. Where the wires connect is pretty big rubber plugs. I'm thinking they have pretty heavy duty wiring because of the winter conditions a grader can run in.