DIY - Build and install a Bussmann RTMR Fuse/Relay Block

It depends on the particular relay itself - it could be SPST, SPDT, DPST, DPDT. So depending on what you want to switch on, off, or combo's of that.

 

Thanks for the wright up! I used all the information as a basis for my build. Didn't come out as good as the OP but I'm pretty happy with it.

 

Big thank you @tacozord ! It took awhile and a few challenges along the way but I did it!

 

Made a little more progress on my build today. Wired the switch panel.

I added a few options not in the write up. Since the switches and relays will mostly be for lighting, I used dpst switches and will tap into the brights as well as the reverse lighting circuits. 4 of those switches will be tied to the brights, 1 to the reverse and all will also have fused ignition 12v. The 6th switch is just a spst switch that will just have ignition 12v power. Thinking I’m going to hook my cb to that switch so I can ditch the cigarette lighter plug I’ve been running. Need to order a couple of terminal blocks for the first 2 switches. I wired the bottom lights to work with the dash dimmer and wired the tops to come in when the accessory is on regardless of if it comes from the ignition power or the brights/reverse power.

Big thanks to the OP for the excellent write up. I never would have tackled this project without it. It’s definitely given me confidence and taught me a lot.

ready to get this thing installed and powering stuff!

 

Looks really clean! Good work!

 

Started my Bussman RTMR Fuse/Relay Block project today. Been gathering the parts for a month now. Time to start.




That's it for today. Tomorrow, adding the cable assemblies!

 

Awesome! I love how people are spring-boarding off the tutorial and adapting the knowledge to their own situation. Well done!!!

 

Looks like a good start! Great work.

 

OK - back to the Bussman RTMR Fuse Relay build. Did all the connectors - used 14 gauge on the right and 18 gauge on the left. I don't need 20 amp on anything right now - 99.999% is done with 15 amp or less. If push comes to shove - I can always switch out a 14 gauge wire with a 12 gauge one for anything that needs 20 amps (like a winch).


Almost completed. Relays in - wired up and tested.
Need a 6 port plug (on order...) now - have to make an Aluminum base for it. I know there are ones out there - but I want something real specific - and the ones that are pre-made are still too basic - so need to go *custom* (as usual)

 

After a few weeks of building and waiting on parts I’ve finally got this sucker installed and working like a charm... I really like this... 10/10 would recommend tackling this project!

 

Currents generally run higher in 12v systems than they do to accomplish the same thing off 110V. A 20A 12V winch might not pull a wheel barrow(most use heavy cable for that rather than “wire”). Even window motors are 5-10A. Even if it still works, running current through undersized wires leads to power loss and voltage drop making motors run slow, lights run dim, and fridges struggle to stay cold. While it’s certainly possible to go overboard with wire thickness, under sizing can be a false economy, especially when running off stored power. You probably already know that but it’s worth repeating. Wire length also affects what size makes a better choice since voltage drop is proportional to length. Some charts provide ohms/ft specs so you can easily determine whether a given size/length is overkill/acceptable/or inadequate to your needs.

 

I'm about halfway through wiring the bussman and have a few questions regarding the OEM style switch. The only thing this will currently be running is a Diode Dynamic light bar. The light bar will be wired into the first relay/fuse block on the bussman. I have a OEM style switch that will be going in a blank in the dash.

I'm planning to piggyback the dash light for the switch (RED 2) off the adjacent fog light switch.

The (RED 1) wire connects to the switch harness and the specific wire in the harness we made for the first relay/fuse block, correct?

My question, what does the (GREEN) wire connect to? The "add a circuit" wire put in our harness? Something else?

If I'm only using OEM style switches, do I need the single "add a circuit" wire and the red/black stripe, brown wire in the harness we made?

 

After doing more reading I believe the (GREEN) on the switch is tied to the "add a circuit" hot/keyed ignition. Since I'm not running a full switch panel, and I'm piggybacking off the adjacent fog light switch for backlighting, I believe I can ignore the two conductor brown, red/black stripe wire. It's there if I expand in the future.

So, GREEN to fused "add a circuit", RED 1 to bussman relay/fuse block for light bar, RED 2 to piggybacked fog light switch illumination, BLACK to ground.

 

Started a build of one of these and really wanted the ground bus bars but had limited room. Was working with a vendor on a new bracket and we discovered that you can just stack the mounting holes of the blue sea mini bars over the RTMR holes to save space. Looks like this (note there’s no ground going to the switch harness as my switches are grounded inside the cab to a variable ground for dimming):



Figured someone might appreciate the idea if you’re struggling for space like I am.

 

Random question which is sort of appropriate for this thread. Has anyone done an in cab aux fuse box? If so, linky to a post or product would be much appreciated. TIA.

 

I'm cramped for space too and I already bought longer bolts to go through the bussman mounting holes, leaving enough to attach the bus bars with a nut on the backside.

 

The green is the power source through the switch to the relay. If you want your lights to work when the truck is off, you need to find a constant power source. I tapped into the "dome" light circuit in the cabin fuse panel. Red 2 connects to an accessory source so the switch lights up with your dash lights. I tapped the "IG1 NO2" circuit for that. The end result is, I can turn the lights on without the accessories on, and the switch lights up when the truck is running. If you want the lights to shut off when you turn off the truck you will need to find another fuse to tap into. Connect the wires to a 9v battery and you can see how the switch works.

 

Sweet, thanks.

 

I put an 8-way fuse panel under the cup holder(manual so it’s actually easier to access than the stock panel) and split the main buss so it’s 1/2 always hot and 1/2 ignition hot. Also added a grounding block. Ground and always hot 1/2 have #10 wire and ignition hot has #18(switch activation power so only a few amps) on an add-a-fuse. Actually 4-#10 wires bundled together come in under the driver’s seat just behind a stock grommet, panel hot&ground, compressor hot, plus an extra for fridge power or whatever. I have on board air with a manifold in the center console so that’s where my pressure switch is and puts that close to my compressor switch.

 

It’s as if we share a mind? I’m of course way behind you but eyeing those grommets today for 4 gauge to amplifiers. Currently running off trailer brake controller but planning a dedicated line.

photo of current state. Gonna hit you up for photos of yours via DM.