A different approach to construction equipment electrical systems


We in the world of construction equipment have always tended to trail along behind the automotive world in many ways, particularly in the electrical systems that we design and use.  The car manufacturers are the 400-lb gorilla in the business, and what they ask for, the suppliers build.  If GM or Ford had demanded, in 1956, an ignition switch that you turned counter-clockwise for “ON”, then that’s what we would still be putting in our dozers, loaders, and forklifts.  As an industry, we have been criticized, and correctly, for being laggards in adopting new and better technology.  Long after the car folks had decreed that electrical connections be nice, multi-pin connectors, we were still hooking individual wires together.  Years after they went to sealed, watertight connectors, we were still futzing around with open, instantly-corroding crap. 


But, in general, we did what they did, if a little tardily.  We accepted the fact that the auto industry was where the innovations were going to take place, and when their improvements were finally available down in the distribution chain at our miniscule volumes, we adopted them and considered ourselves wise.


I think that the time has come for us to part ways with the car guys. 


Their world has increasingly diverged from the world that our equipment works in.  Most of the electrical system in a modern car is out of place in construction equipment.  Here’s a partial list of things that I have to contend with on every piece of equipment I design:



  1. Most of the switches on cars are stalk-mounted on the column. These are all tiny, delicate, gracefully-designed bits of plastic that the average ballerina could snap off like she was picking a flower.  The average male equipment operator doesn’t even notice he brushed against it until he sees it swinging from its wires.  If something in my world is long enough to get your hand around, then it by gosh better be strong enough that Bubba can do chin-ups on it.


  1. The automotive interior design dictates of stalk switches means that the switches themselves are physically tiny, and the wires to them must be hair-thin to go through all the holes. This, of course, means that the switches have proportionally tiny current-carrying capabilities, and so whatever they control must be actually switched by a relay.


  1. Because of this and other real concerns, it has become fashionable in the automotive world to incorporate a relay into every function. This has led to the universal adoption of tinier wires and tinier switches, even on functions where there’s actually room for big switches and wires.


  1. Switches on cars are always indoors and thus not sealed. On the equipment I design, cabs are optional.  That means the switches are out in the rain, or worse yet, the washbay.  And if the car guys don’t seem worried about water intrusion on in-cab stuff, they don’t even know that dust exists.  Or dust and water together.  Or road salt.  Or salt used in aluminum smelters.  Or the corrosive dust in fertilizer plants.


  1. Ignition switches are also a problem—they have long ago been incorporated into the steering column, and tied into the steering lock, and lately been vested with all sorts of new responsibilities, to the point that a key blank costs about $100 and has a microchip in it. The automotive world hasn’t designed a nice, simple dash-mounted keyswitch since about 1960.  And that one wasn’t waterproof.


  1. As the gasoline-engined automotive world has gone to smaller switches, the diesel world has been seemingly going to larger starter solenoids, to the point where now the trigger circuit on a small Cummins engine draws 70 amps inrush current and thus has to have a relay. That’s a relay to fire a relay.  That’s three sets of contacts, and two coils that have to work just to tell the starter to get going. 


  1. Auotmotive gauges have long ago been integrated into nice plastic pods with all two gauges incorporated in a display with six hundred idiot lights, and all covered with a piece of clear plastic. I always laugh when people get going about how plastic lasts a thousand years in a landfill.  It might do that if you bury it, but if you leave it parked in the sunlight, it will be dust in a few years.  Of course, it will have faded and crazed to the point that you couldn’t see through it long before that.  Plus, we still have people who like gauges for water temp and hydraulic temp and transmission temp and so on.  Vendors still exist for that stuff, fortunately.  They mostly haven’t gotten the word on sealed connectors, though.  With the advent of electronic engines, the gauge problem is getting solved (or getting more complicated, depending on your outlook) by being incorporated into the engine control computer and its display. 


  1. I already touched on sealed connectors, one of the greatest things we ever inherited from the car world. The only problems with that is the trend to itty-bitty wires—some of the newer connection systems can’t handle anything bigger than 16 gauge wires, and the current capabilities are correspondingly small. 


  1. One of the things we need to adopt that some of us haven’t is the better-quality, high-temp wire insulation—SXL and GXL is the designation. No reason to use the low-temp junk.  I have a few pieces of wonderful Kapton-and-Teflon insulated wire from my military aircraft period.  I wish I could use that stuff for everything.


  1. My opinion Statement of Fact above regarding plastic gauge faces may be re-read with regard to work lights. Most suppliers have figured this out and offer both glass and plastic lenses. Plastic lenses on lights is one idea that doesn’t even work in the automotive world, despite its universal useage.  Go find a ten-year-old car with transparent lenses.  Bet you can’t.  I’d accept plastic lenses if you could replace them for five or ten bucks, but the ones I am ordering for my wife’s car are going to be a hundred and fifty or so.  My truck has been retrofitted with proper all-glass sealed beams, thank you very much.  Last set in the world, maybe.  And yes, I did hit a nerve on myself, there.  Kind of a pet peeve in fact, on which I could go on for about an hour….


So what do we do to cope with all this?  Here goes:


The boating industry has saved us on the switch issue.  Carling and Otto make excellent watertight rocker switches.  They are about the only thing we use anymore.  They are good stuff, but you have to have some room, because they are big.  I prefer to buy the non-imprinted ones, and do all the labeling on the dash panel.  It takes up more room, but you can cover just about everything with 4 switch part numbers.


The bass-boat suppliers are also our go-to guys for dash panels.  We found a company who would make a beautiful black lexan panel, with milled lettering or hieroglyphics for the switches, for about what we had been spending for the decal alone.  The machined lettering never rubs off or washes off, and allows you to backlight the entire panel.  Wonderful stuff. 


Ignition switches are still a sore subject.  The boat people have some pretty nice ones (Hobbs, for instance) that are watertightish and have the nice-looking plastic-handled keys.  They won’t handle starter current, technically, but don’t melt immediately.  Far better than the dismal stuff from Indak, Pollack, and Cole-Hersee. 


I’m thinking of doing my next project like this:  the dash will have the usual gauges and switches for various things, but the “ignition switch” will be one of those huge “master disconnect” switches that can actually handle the full starter motor current.  Stay with me, here.  That switch will power up the entire fuse panel without a relay.  The starter switch will be a separate pushbutton that can handle the start solenoid’s 70 amps without a relay.  I think Trombetta has something that will work, or I may go to the ancient Cole-Hersee button with a rubber boot over it even though the back isn’t sealed.  That eliminates two big high-current relays, but loses the key-switch anti-theft function.  Like an everything-keyed-alike switch was ever much of a deterrent.  So anyway, the final touch that makes this all work is a hinged, flip-up vandal-proof cover over the entire dash, with a keyed (non-electrical) latch.  The cover will flip up and maybe the back will be useful for the instructional and warning decals that we can’t ever find enough room for.  The panel latch can be sourced from the same people who supply the cab-door latches and engine-compartment latches, so we will have the opportunity to key everything alike.  The panel can easily have a set of holes to take a padlock for the next layer of theft/vandal protection.  That’s the plan, anyway. 


I will also split up some of the switch functions to eliminate relays where possible.  Front and rear work lights, for instance, will be on separate switches.


Sealed connectors come down to either Packard Weatherpack or Deutsch.  I saw an ad for some new Amp sealed connectors, but have never actually used them.  Deutsch has a much better selection than Packard, and used to be more expensive, but lately they seem to be about the same.  Much as I hate it, we generally wind up with more than one kind of connector, because somebody’s component will have a Metri-pack or whatever built into it.  Not much you can do in that case except go with the flow.


We always try to spec the better high-temp wire, and push for using the good triple-wall, glue-filled shrink tubing on splices.  Where we have splices or ring terminals, I prefer to use non-insulated terminals and heat shrink.  Nothing says “hillbilly” like the blue or yellow plastic insulated crimp terminals.  Deep down, I’d like to solder them in addition to crimping them.  I’ve never actually convinced anyone to do that.


We’ve had some animated discussions regarding colored wires versus imprinted wires, and I don’t really have a solid opinion.  If it’s something I am mechaniking on, I like colored wires.  If I’m the guy doing the wire harness drawing, I like numbered wires.


Nothing is better for tail lights than what the semi-truck industry uses.  Sealed, grommet-mounted LED lights.  The connectors are not quite up to rest of the system, but that’s begun to change.  The lights are wonderful, and cheap, and available.  One odd problem I heard of in Canada is that they won’t use LED taillights because they don’t get hot enough to melt off the snow and ice.  Hadn’t ever thought of that…


Lots of indicator lights are designed for interior use, and you can’t see them in the sunlight.  If you have some room, and you want a really good warning light, use a truck clearance light, mounted in the dash with its normal rubber grommet.  That will get someone’s attention.  There’s a very nice little ¾” grommet-mounted LED unit that is getting popular on trailers, and it’s become my favorite.


Work lights used to be Hobbs most of the time, for us.  They were glass sealed-beams, and most other brands are designed with a separate reflector, lens, and H3 bulb.  I do have a set of ABL lights undergoing extended testing on my own farm tractor, and they haven’t filled up with dust or water.  That may be the ultimate, since H3 bulbs are only about $5 to replace.  Come to think of it, I believe I tossed the 55watt bulbs and put in 100watts when I installed them.  Even more impressive!  By the way, my field testing indicates that even on the huge Cepek Baja Lasers, the 130 watt bulbs are a waste—no more light output than the 100s, but burn out much quicker.  But all that’s pretty obsolete, now that LED lights have become competitive.  ABL is the only brand I’ve used so far, but I see a lot of plastic-lensed junk on a lot of equipment, and it’s fogged and crazed in a couple of years.  We need to do some research on that, soon.


When suppliers try to sell you electrical stuff, and they make any claims toward water resistance, take their samples and mount them on the wall in the wash bay.  Tell the wash guy to spray them a few times a day.  Go test them every few weeks, and you will soon sort out the good stuff.  Did that with backup alarms once a long time ago, but can’t remember which brand won.


I hope I never design anything with electrical stuff “under the dash” again.  By far the nicest way is to have a dedicated compartment somewhere that you can mount all the fuse panels and relays in, and have it accessible from somewhere comfortable.  Even better if the gauges and switches mount on the top panel of this box, so the backs of them are visible from the fuse panel.  Let me clarify that “accessible from somewhere comfortable” does not mean lying on your back between the seat and the door hinges, and looking up into a dark cavity surrounded by sharp sheetmetal edges, with room for exactly one hand to find, strip, crimp, and heat-shrink.  Look at a John Deere loader from the mid ‘90s.  They have a door on the right side of the cab that gives you access to just about everything, plus a nice flat step to sit all your tools on.  Very nice.  Now figure out how to design that on a skid-steer.


Another note on wiring in general:  pay attention to what the boat people are doing.  They do a lot of small-volume machines, they know more about corrosion-resistance than anyone, and their vibration environment is similar to construction equipment.  I’ve run across some really good blogs by specialists in marine electrical systems, and learned a lot from them.


Jess Davis  4-23-2020

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