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

Thank you for responding, but in the meantime I figured it out.

 

@tacozord

I searched this thread but didn't see anything. Do you think it would be alright to use speedwire for wiring up the switches? I'm thinking it will be way easier going through the firewall.

 

Tacozord used 18awg more for the sake of handling and durability but smaller wires could be used. They only carry ~ 1/10 A to trigger the relays. You could use glue lined heat shrink to still fit tight into the wire seals if you can’t get the right seals. But pushing the terminals into the Bussman or removing them if necessary is where you might see the real difference. The firewall grommet can easily handle the bundle of 18’s and then some.

 

Speedwire is a group of 9 18awg wires in one outer sleeve.


TOPSTRONGGEAR 20 Feet 9-Conductor Speaker Cable, 18AWG 100% OFC, 4-Channel Speaker Wire and Remote Wire (18 Gauge)

$24 TOPSTRONGGEAR 20 Feet 9-Conductor Speaker Cable, 18AWG 100% OFC, 4-Channel Speaker Wire and Remote Wire (18 Gauge)

https://www.amazon.com/dp/B09198F1B4

 

I’d think that would be great as long as it can tolerate some heat. Might just need some split loom since it’s advertised as easy to strip. Nice that it offers a few extra circuits for accessories over 30A that require a separate relay from the Bussman, something I needed for my install.

 

Yeah I would put split loom on it from the firewall till the grommet. That will protect it and make it look more like factory too.

 

I did not use any add-a-fuses in my build. The RTMR is wired directly to the battery, in cab switches are spliced into ignition controlled power on the dimmer circuit. I forget exactly where I spliced in.

 

I know (hope? lol) you're probably long done your project but maybe this helps someone.

edit: the drawing scale is 1:1 so you should be able to just print it out if one wanted to see how it fits

 

Indeed, better late than never! I did finish it but it could use another look. It's by no means purty.

 

Well, I think about a year and a half after I started this project, I finally got it into the truck. It’s been so long I forgot two things:

<edit: okay, checked my picture album and it’s been three years.>

1. That the Powerworks tray I have conflicts with the spiker engineering hood struts I have. Way back when, I figured out how many washers would make the right size stand-off and taped up two stacks so I’d have them ready to go. I’ve been pushing them around my tool drawers for over a year. The tray’s a bit of a bitch to put on with how I’ve routed my pigtails. And of course I didn’t remember the fit issue until I got it all nice and snug. Got to work that process again

2. I never ordered the male pins for my accessories. so off to Amazon I go and order the minimum quantity which is about three times what I need. Another week of waiting. Strange, the female side of everything seems to be available tomorrow. The make half is usually 5+ days out.

So… it’s installed and powered, but nothing connected yet. I still need to run my control lines into the cab but I have that cable all made up and ready to go. I have all the necessary switches too. I think I’m going to figure out some sort of strapping or clip system for the top of the fuse box to organize the pigtails.

It’s been said many times, but kudos to the OP for all of his work putting this together. @tacozord. @Mr.PowerTrays

 

who makes a reasonably priced generic mounting bracket for a Bussman RTMR these days?

 

Shame the OP doesn’t come around anymore. Almost 10 years later, this is still one of the most well-thought out and informative posts ever drafted into existence on TacomaWorld.

 

Sharing mine to contribute back to this great thread. Years ago I bought one of the surplus Pelfreybilt panels from BAMF not knowing the whole story there. Still worth it but I did a little customizing. Didn't like how small the bolt holes were for the breakers so I drilled out to 1/4" which fit a Blue Sea 285 much better.



Since I live in the salt belt, wanted to give the bare aluminum some protection. So I sanded & painted with an aluminum color paint and it came out looking pretty darn good.





Was on a time crunch before a road trip so I only built out the panel this far and plugged the remaining open cavities. I'm waiting for some accessories to show up in the mail so nothing to plug in yet, but it won't take long to finish. Notice I was also able to mount the bus bars on the RTMR bolts which saves a bit of clearance to the panel mounting bolts.



Installing the two bolts on the fender are kind of a PITA but once it's in it ain't going nowhere (I slapped it to confirm as is the custom, it's good). Spiker Engineering hood strut just clears the RTMR cover.



Full view from overhead. One breaker is for the RTMR, the other breaker is for my house battery charging system. Overall it allows for a pretty dang clean install. Can't wait to start adding accessories.

 

Hi new user here. Amazing write up!

I had some questions based on some of the images I came across in this thread (shown again below) I'm wanting to have a Bussman 15401-2-0-1-0A RFRM configured as follows:

1. All 40 fuses work and all have 12v power going to one side of the fuse, just like an automotive factory fuse box would have.

2. All 10 relays work, where pin 86 is trigger and pin 87 is 12v+ out, and all are grounded. If a relay is ground triggered, can the relay simply be flipped or is rewiring needed per the diagram below and wiring it as such won't work?

3. Pin 87 and 86 for each relay go to a 2 pin connector, for a total of 10 connectors. Fuses 1-20 on one side route to a 20 pin molex connector, and fuses 21-40 on the other side go to another 20 pin molex connector. Is the 20 pin pictured good, or should I get something different like a metripack? This fuse panel will be mounted inside the car. Then simply pin into the other side of the molex connector which will lead to the various items needing fused. Note that fuses 2,4,6,8,10,12,14,16,18,20 (when looking on the front of the unit) go to relays 1,2,3,4,5,6,7,8,9,10 respectively. So relay 1 is tied to fuse 2, relay 2 is tied to fuse 4, relay 3 is tied to fuse 6,and so on. Figured this is better than trying to wire say Cavity A11 all the way up to E1 just so that fuse 10 goes to relay 10 and all the fuse numbers and relay number match....that would make for a wiring mess.

I think my image is incorrect in that I need to remove the wires going between cavities A2, A4, A6, A8, A10, A12, A14, A16, A18, A20 and the respective pins 19,17,15,13,11,9,7,5,3,1 on the 20 pin molex respectively as pictured below. Since power is already going to the bus, no need to run additional wires for those fuses and instead just use a 10 pin molex on that side instead of a 20. So 10 fuses will be dedicated to 10 relays, and then 30 fuses available for other items. Is that the correct way to do it?

The "External Ground" is just a long busbar that I was planning to add in addition, so that anything connected to fuses 21-40 sees 12v.

Am I going about all this the wrong way?

 

Is this correct? Maybe I should connect pins 30 and 86 together for some of the relays so that pin 87 can be used as a trigger for items that need a negative trigger rather than a positive trigger and pin 85 can go to the device for those few respective relays...

 

I suggest you study the OP a bit more. Not to be glib but to give you more time to mull things over. List your accessories and find out if they actually require a negative or positive ground. Also, while the RFMR you reference is compact it has a shit ton of wires and connectors that will need to be accessed in an inadequate space. It can be far easier to disperse the wiring to two or more panels like the way sub panels are used in a house. You might also consider a panel with a single buss for the fusses so you can wire each relay as you please but keep in mind positive and negative triggering affects not only the panel but how you wire the switches. Mixing both could be a nightmare and seems unnecessary. Pick one for the switches and stick with it, you can still have the relay supply power or ground to each accessory.

 

Yeah I'm just trying to get an idea on the wiring of it. I plan to label everything with printable heat shrink tubing. Say I wind up with 6 relays that are positive trigger and 4 relays that are negative trigger, if I set it up like this in the new image below, I can have 20 fuses for things that only "accessory." That leaves 10 fuses remaining for the 10 relays, and 10 fuses that are 12v+ from the battery. Then run a big 60 amp stereo type fuse in line with the battery cable (3 feet max of 10 awg) to the ignition switch. No relay needed between ignition switch and small fuse panel as what I'm running off that small fuse panel will easily handle the draw. There's not really going to be any high amp draw circuits in the main fuse panel. Maybe I'll run an ignition relay so that I can pull large wire direct from the battery just in case if the need arises. If I ever need to remove the entire fuse/relay box, I simply disconnect 10 pairs of 2 pin connectors, a 10 pin connector (12v+ fuses) and a 20 pin connector (20 accessory fuses) and the 3 wires leading to the battery.

 

it was my understanding that the RFMR has 20 fuse slots rather than 40 so you might only need the ten pairs and one 10-pin connector.
For 60A I’d bump up that cable to #8 or #6(I used #4 for 80A).
Nope it’s 40 fusses with slots for spares. Good luck with that.

 

As someone who stubbornly insisted on installing an RFMR so I had more relay circuits...go with @bagleboy 's advice and fork your needs into two subpanels. There is literally not enough space between the brake reservoir, fuse box, and engine to fit all the wiring you'd have to have for the RFMR. I had to ditch half the fused circuits because there simply wasn't enough room, and it's a super tight fit as it is. Getting the fuse box cover off and on is a major PIA, to say nothing about how much it sucked to install it and the supporting bracket.

One day, I'll put an RTRM in the engine bay to replace my RFMR, and put the RFMR in my bed. Or sell it.

 

They make outstanding products but I think the RFMR is better suited to a different location if you have that many circuits to run(camper rig). I won’t try to speak for anyone else but in my case with a mix of in-cab accessories, bed accessories & engine bay accessories it just makes more sense to have separate panels in order to limit wire lengths, cab wall penetrations, and cable densities.