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

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One add-a-fuse can supply power to all the switches if they’re just for relay activation(~100mA per switch), otherwise you may need independently fused switches and probably better switches since these are typically limited to <3A. The source you choose for the add-a-fuse(s) should reflect whether you need always hot or ignition hot for the accessories. My rear window slider taps the door lock fuse(always hot with switch mounted in door armrest) the center console switches share power from an add-a-fuse that taps a low amp fuse and supplies a small fuse panel in the center console. The slider switch gets illumination power/ground from the window control harness so only two additional wires had to go through the door grommet. All other switches get illumination power/ground(red 2), black) from the dash illumination circuit so they illuminate with headlights on and dim just like the other switches. I bumped the resistor in the slider switch to 20k ohms which makes it a good match for the only other led in the armrest controls which also isn’t on the dimmer circuit.

 

Your fuse bar is exactly where I mounted my ground buss.

 

Yeah, the bussman is really overkill for what I currently have and what I have planned. However, I wanted to future proof (or at least make it easier) to add things as time goes on. For now, the single switch is what I need, and I'm planning to wire it as you described, just for relay activation and mimic the backlighting piggybacking off the adjacent OEM switch.. I'll maybe add one more switch but after that I would look at a switch panel, but I'll have the harness already in. So adding a switch panel shouldn't be too big of an issue.

The last couple of days I've been working on building harnesses, swapping out headlights and that harness so I can run the upgraded bulbs, installing a light bar and now finishing up the bussman wiring. I'll be finalizing the bussman wiring tomorrow.

 

Whew. Done. It took four days but I swapped headlight housings back to new OEM, added new headlight harness, changed my hidden light bar to a 30" DD combo, built the bussman and got everything installed. Hit the power and everything worked like it should first try. @tacozord did a great write up. It is drinking from a firehose when you first start, but once you get into it it's pretty easy. It's just time consuming, especially building the harness plugs. It was a great project to do over the holiday as I could take my time and not rush. Thanks @tacozord

 

QQ where's the cheapest place right now for parts for one of these?

 

Depends on the parts you are looking for. I have left over parts that you have to buy a minimum of and I’m willing to get rid of them.

 

Delcity if you can wait for one of their free shipping periods. Their moqs are such that you don’t need to order enough for a bunch of kits.

 

Great job! Looks fantastic.

 

Thanks and many thanks to you @tacozord for the write up.

 

I just got a dual amber/white light bar and need some help hooking it up. The light bar has 3 wires: yellow (negative), blue (positive), and red (positive). I need to figure out which positive goes to what (white or amber), which should be easy. I have 2 switches in the cab designated for the white and amber independently, so I will be using 2 of the plugs on the Bussmann. What is the best way of going about splitting that one ground wire so that both plugs will have a ground attached to it?

 

Not necessary to split it. It supplies ground for both led circuits so run that one wire back to the ground buss, battery, chassis. Your switches supply the positive voltage via the two relays they activate.

 

I had a sneaky suspicion that was what was happening (I’m not the best with wiring). I’ll try to hook them up today and report back. Thanks!

 

It’s much the same as your switches which have two leds that have different power sources but share the same ground.

 

So I connected the ground wire of the light bar to the ground bar on the side with the relays.
I then connected the blue (pos) and red (pos) wires of the light bar to the appropriate plugs on the relay side as well, but the lightbar will not turn on.
The lightbar works because I connected the 2 plugs to the “always hot” side of the Bussman and it came on then.

 

You sure you connected to the correct (+) pin on the plug?

 

You mean the “A” side of the plug (which would be the positive side)?
If you mean that, then yeah I checked that.

 

Assuming you have it wired correctly, either the switches aren’t activating the relay, the relay isn’t powered, or ground isn’t good. Pictures help but half the time a connector is plugged in but not making good contact. I’m seeing this occasionally with these aftermarket green plugs. A meter can tell you if you’re getting voltage. Continuity checks don’t always
pan out since it can beep but still not pass enough current to activate a relay. Also make sure your relays are installed in the correct orientation.

 

Check for voltage from pin to grd buss with meter?

 

What I’m thinking is that the female connectors inside the quick disconnect of the harness behind the sunglass holder are bad.
I already wired up a pair of camp lights and had no problems with the install of them.