Isolating a 5 wire trailer

I purchased a Aluma MCTXLB trailer which uses a 5 round plug which works really nice with the FJR unless you want to use a Hopkins 46365 short proof adaptor.

I installed the trailer wiring using the Amore Lighting adaptor “PLUG N PLAY ADAPTOR FOR YAMAHA FJR (GENll/lll) product code A-FJR2” along with the existing plug n play power harness used with the Givi e55 lighting upgrade. So basically you are able to do a “plug n play with another plug n play. Made it real easy.

I was able to go from the A-FJR2 adaptor to the trailer connector socket.

I purchased the Hopkins 46365 short proof adaptor but now it seems I’m converting my 5 wire set up to a 4 wire and my trailer is a Aluma 2018 MCTXLB which is a 5 wire system. Now I have to decide how to isolate or not at all. I'm searching for the answer now.

I found this at ETRAILER.COM. Copy and paste https://www.etrailer.com/question-10460.html%C2

Isolating Power for a 5-Wire Motorcycle Trailer Harness and a 5-Wire Motorcycle TrailerQuestion:


I want to use an isolation set up on my motorcycle/trailer, both use a 5 wire set-up, the trailer is a 5 pole flat with the last wire for the brake lights. any suggestions?

asked by: Steve C
Expert Reply:


There is a way to isolate the power draw on a 5 wire to 5 wire setup, but it would require a few parts and some wiring work. All of the isolated power trailer converters convert a 5-wire vehicle to a more standard 4-wire system for automotive use trailers, but as you are aware, motorcycle trailers are built as 5-wire systems to match the bike.

You would use part # 119179 on the bike. This part has 5 wire leads to connect ground and the different light functions. The 6th wire is the battery wire so that the trailer lights will have their own power circuit instead of drawing power through the motorcycle tail lights. You would then connect this new trailer connector to a 4-Pole trailer side connector like part # 9653P.

From this 4-Wire connector, you can up-convert back to the 5-Wire system using part # 118158. In essence what is happening is you are converting from a 5-Wire to a 4-Wire when you isolate the power source. You then connect to the trailer. Finally you convert from a 4-Wire back up to a 5-Wire before getting to the trailer light.

It is a bit of a round about way, but these are the only parts we have available to accomplish this.

expert reply by: Patrick B

That sounds like a PITA, and I have no idea how to do any of it. I'd think someone makes an adapter to do exactly what you're trying to do. I know vehicle trailer lights, but have never done a MC.

I'm just going to run the lights with out isolating because they are led. Everything is brand new and seems to work great. F- IT! LOL I'll check on things now and again and deal with anything that comes along. Thanks for the reply Zilla

looks like openroadoutfitters.com has a five wire trailer isolator for 109$ seems pricey

It sounds like what you want is some overload protection so that a short circuit in the trailer wiring doesn't take out the signal fuse on the tow vehicle, right? That would be a fairly inexpensive thing to build into a small project box with a few fuse holders. I'd go that route before forking over > $100.

Yes, Mostly overload protection. BUT also like the idea of powering the trailer lights via the battery. I'm praying with the extra lights( givi lights and trailer lights) being led it is not to much load on the factory wiring. Thanks Fred

Well I took the easy way out and forked over the money.

Like i said above I have Amore Lighting adaptor “PLUG N PLAY ADAPTOR FOR YAMAHA FJR (GENll/lll) product code A-FJR2 so I don't have to cut the bikes wiring or use the scotchloc connectors that come with this Universal Trailer Harness for 5-Wire Trailer from www.openroadoutfitters.com .

It will power the trailer lights off the battery and isolate the trailer circuit from the bike circuit. And I don't have to adapt from 5 wire bike to a 4 wire isolator and then adapt back to a 5 wire trailer. I think this is the best long term solution.

Installed the isolator and it is a very nice product.

All the relays and wires and connections are potted into one little unit, way nicer than the cobbled mess I may have built.

Word of advice would be to install Admore Lighting's plug n play, A-FJR2, connect that to the input of the isolator THEN use a 12v test light to identify/label the right-turn, left turn, Tail/running, Brake and ground. After you label them it's easy to connect to the proper wires going to the proper pins to your trailer connector. Don't go by wire color.

I connected the power and ground wires from the isolator into my fuse block, on the switched power side with a 3 amp fuse. I can verify the isolator works with the 3 amp fuse because I did short it out, on accident, when i was testing the lights at the round 5 pin connector before connecting to my trailer.

I did pull the trailer, without the isolator 800 miles with no problems. I'm sure in the future i'll be glad i installed the isolator.

THE END.