Mercer

Ray,

I wired it into the cab. It was a lot of work, partly because I wanted it to look like a factory job. I'll take some pics and post them with descriptions of what I did later today.

I hope you'll be able to get detention.

 

The Fontaine trailer I bought last summer came with ISO 3731 socket (one with yellow wire sticking out) in addition to a regular 7-way ABS wire (green). The dump valve came hooked to the black wire on the ISO socket from the factory.




So I bought an ISO socket and ISO coiled wire from Ryder fleet products, and made a new bracket to hold two sockets and air lines. The original bracket looked about the same, except there was no place for the extra socket.




I assumed the original bracket was made of aluminum, so I used aluminum of the same thickness. It turned out the original was stainless. Naturally, the new aluminum bracket flexed way more than I liked. Rather than making another bracket (our bandsaw and sheetmetal brake wouldn't handle 0.100-inch thick stainless), I made a brace with some steel I had laying around. I sprayed it with cold galvanizing spray.




I bought 25 feet of a standard 7-way wire from a local truck parts supplier, hooked it up to the socket, and ran it parallel to the other 7-way wire all way to the firewall. I pulled one of extra rubber plugs on the firewall and found a grommet that fits in the hole properly on McMaster-Carr website. The only problem was the inside diameter on the grommet was 0.75", and the wire's outside diameter was 0.625". The black plastic grommet takes up that gap. Both grommets are rated for under-hood temperatures.




The wire fed through the grommets and the firewall. I put small fuel hose clamps on the wire to keep the plastic grommet from popping out the orange silicone grommet. Aesthetically, this orange grommet is the only part I'm not happy with, but fortunately, it's not very visible.



New wire zip-tied to other wires. It will blend in with the rest after a couple months.



The dashboard bezel pops out with gentle prying with a screw driver. Instrument panels are screwed on, and came out without any fuss.



The truck came with a blank switch labeled "SPARE". It was located right next to the ignition key hole, and I just relocated it to where I want it. One side of the switch is already hooked to 12-volt source, so I simply hooked up the black wire from the 7-way wire to the other terminal. The white wire was hooked to the main ground terminal.




So after 3 days of leisury-pace labor and 250 bucks or so, I have a functioning dump valve. I could have done it cheaper, but I chose to retain the ISO socket and used a 7-way wire. I went this route because...
1) I didn't have to do anything to the trailer
2) I can add 5 other auxiliary circuits simply by taking the dashboard apart and adding switchies.
3) Reliability - all wires are covered with heavy vinyl jacket the entire length, and all the connections are covered or under the dash.

Just by running circles around the dirt lot, the difference is apparent. With the air dumped, the back axle gets dragged instead of the front axle making tight turns. It should help quite a bit when loaded heavy.


Future revisions/corrections
- I assumed the 12V source coming into the switch has a fuse. I've yet to locate it on the fuse panel, so maybe it is not. I'll splice in a fuse on the black wire just in case.

- The little dot visible on the lower side of the switch is supposed to light up when you push the switch. It worked until I actually hooked it to the trailer. I need to figure out why the LED burnt out.

 

very nice job--better than if you had taken it to shop that is for sure

 

nice job Katz, and great write-up on how you did it. I don't have the socket, just a wire tucked up in the front corner that needs to be connected by whatever method I choose. I need to move my air lines and electric cord too, but haven't decided where would be best.

 

Thank you guys. Some pics appear as red X on my screen, but when I go to Edit, the pics show up so I'm not sure how I can fix it.

Planning is half the battle. Skipping this stage would result in having to make adjustments as you go along, possibly having to buying more materials because you screw up the first time, just like I did LOL.

 

Looks great ,

 

Real nice job! I drove for a guy who had one rigged up by a shop in Houston by some criminal illegals. Going up 25 from Denver wiring caught fire filled cab w/ smoke. Made quick 1st trip to Johnson's Corner. Pulled in w/ expandable step pulled out to 87' total length. Broken window switch so only fresh air was from door propped open w/ foot. Finally managed to jerk all the rigged wiring from under floor mats and behind dash to stop fire. No fuse. No proper connections. ETC. Just the way they teach them in Mexico. Taught him a lesson about his "deals" he always bragged about to me. Did find good stop so it wasn't a total loss. Your job looks 1st rate. Make sure on the fuse. No fun to be rolling 70mph and have to hit a ramp in smoke filled rig.

 

Appreciate the compliments!

That must have been gotten your heart rate going! Glad you got out unscathed. Looks like I got another day off, so I'll go splice in a fuse.

Hope all is well on your end.

EDIT
Found out the 12V power coming into the switch is coming from a 15A circuit breaker on the fuse panel.
I'm still trying to figure out why the LED on the switch burnt out. I've been thinking that perhaps the dump valve consumes a fair bit of amperage, causing voltage spike, but it appears it only consumes about 1.35A so I'm not sure if adding a relay will help this.

 

Katz, I have the same problem with the light on my switch. Not sure why.

 

I've yet to find the cause, and I'm not sure if I'll pursue.

I took another switch apart (one for lights on the headache rack), and put its LED in the dump valve switch. Same result - the green LED lit until I hooked the wire to the trailer, and it burnt out within a few seconds of activating the dump valve.

So now I have two switches with no LED indicators. A local KW dealer quoted me $90 for a replacement switch. Ouch. So I'll just live with it, since the dump valve has been working with no problem.


I came to Birmingham with a 31k-pound 40' can loaded at the back of the deck, and the dump valve sure came in handy. Aside from the obvious benefit of reduced stress and wear on axle/tires, it made it much easier to get going and shift while making tight turns from dead stop (eg, making a turn at the top of an off ramp to go to a truck stop, etc).