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907ie wiring modification confusion

Posted: Fri Nov 08, 2019 7:51 pm
by BillB01
I was about to do the wiring mod that involves adding a relay to isolate the ignition switch from the main power. This:
https://app.box.com/s/64zvqpl6sf303gt44wu6

The images and comments below illustrate my confusion. There are various versions of this mod description scattered around the forums. Most are unclear about how to wire this relay. I found one write up regarding the Paso 750 that I thought spelled it out:
http://www.desmodemon.com/paso_project_5.html

Maybe this is obvious, but, as usual, it wasn't to me, and the description linked in the 907ie FAQ could mislead someone who is electrically challenged, like me.

Carry on.

Re: 907ie wiring modification confusion

Posted: Fri Nov 08, 2019 10:10 pm
by nickta
Hi Bill.

The relay is going in to take the load (current) off the ignition switch. The contact of the ignition switch cops the brunt of it, with everything except the starter current going through them. I don't known what the current rating of the switch contact is, but they were designed and built in the 90's using that era material. The contact rating of a relay can vary, and even the standard car relay can handle 10 to 15 amps with little trouble. The idea of the mod is to use the crap contacts of the switch to turn on the relay contacts, which then has the capacity to run the bike. The coil resistance of a car coil is relatively high, so current required to make and hold the relay is low, which takes the pressure off the ignition switch.

Hope this helps as an explanation. If you need a bit more info, drop me a pm or another post here.
Cheers
Nick.

Re: 907ie wiring modification confusion

Posted: Sat Nov 09, 2019 3:09 am
by BillB01
Great stuff, Nick. Can you confirm the wiring of the relay is as shown in the last image and not the one in the actual 907ie file?

Re: 907ie wiring modification confusion

Posted: Sat Nov 09, 2019 5:41 am
by nickta
BillB01 wrote:Great stuff, Nick. Can you confirm the wiring of the relay is as shown in the last image and not the one in the actual 907ie file?
Hi Bill.

If it was me, I would connect the 12v to Pin 30 and have the switched 12v on Pin 87.

http://www.desmodemon.com/paso_project_5.html


It will work the way it is, but convention (if you can call it that) is to have 12v on the fixed of a switch. No idea why?

The middle picture is probably the way I would wire it up, with a 4 pin relay. The bottom pic has a 5 pin relay, which has one pin not connected? The top picture is missing pin numbers, but starting at the top and going clockwise, they would be: 87, 85, 30, 86.

One further thing. Always have a fuse in line with the 12v to pin 30 of the relay (assuming you connect it to pin 30). If there is a fault with the relay in the future, and you short 12v to ground, you will blow the fuse. No fuse and you may end up melting a lot of insulation and sparks and what not. Worst case is fire under the fuel tank, which could really ruin your day. It is possible to use the existing fuse holder under the seat, if you want to make it look pretty, but an inline fuse holder is cheap insurance. You just have to remember where you put it! :banghead:

Hope this helps.

Cheers.

Nick.

Re: 907ie wiring modification confusion

Posted: Sat Nov 09, 2019 5:28 pm
by BillB01
Oh, so it will work either way. My electrically challenged mind finally sees that. In retrospect, it seems obvious. Sorry to be polluting the forum with my confusion. You spelled things out so even I could understand it. Thanks.

Re: 907ie wiring modification confusion

Posted: Sat Nov 09, 2019 6:13 pm
by Mc tool
The whole point of the forum is to ask ,and when you do 3 other blokes read the answer and "get it " too.......so it all helps

Re: 907ie wiring modification confusion

Posted: Sat Nov 09, 2019 7:54 pm
by BillB01
Yes, now I see it is a bit odd that the Paso 750 document shows 30 swapped with 87, but I get that it makes no practical difference.

And Nick, thanks for the idea of using one of the unused spots on the exiting fuse box.

And one other questions... What would be "the proper sized wire" for the power wire in this case?

Re: 907ie wiring modification confusion

Posted: Sat Nov 09, 2019 11:40 pm
by Mc tool
There is a minimum size , and most manufacturers hit that every time . I use 4mm for heavy stuff like headlights and coils and charging system , and 2.5mm for the rest . The idea being that the larger the cross sectional area of the conductor the less voltage drop .
I use one relay for the main relay but the second is for the coils and magic box ..... I have 2 more up front for the hi low beams ........probly a bit of over kill :)

Re: 907ie wiring modification confusion

Posted: Sun Nov 10, 2019 12:18 am
by BillB01
Oh, the coils. I saw that the "Paso 750 Project" included a relay for them as well. I believe the 907ie ignition relay covers that. I'll check.

Re: 907ie wiring modification confusion

Posted: Sun Nov 10, 2019 4:31 am
by Mc tool
Yeah , I keep forgetting the 907 is different there so,probly not needing a relay for that

Re: 907ie wiring modification confusion

Posted: Sun Nov 10, 2019 1:00 pm
by Willo
Mc tool wrote:The whole point of the forum is to ask ,and when you do 3 other blokes read the answer and "get it " too.......so it all helps
I couldn't agree more. Not many know it all and we can always learn something.

Any more of you out there with questions? ASK AWAY.

Re: 907ie wiring modification confusion

Posted: Sun Nov 10, 2019 8:50 pm
by Mc tool
Willo wrote:
Mc tool wrote:The whole point of the forum is to ask ,and when you do 3 other blokes read the answer and "get it " too.......so it all helps
I couldn't agree more. Not many know it all .
Oh , there have been a few,.........funny thing is ,they never seam to hang round long :evil: :thumbup: , after a) we start asking technical questions , and b) they realise WE (collectively ) know our stuff and thusly cannot be bullshitted :)

Re: 907ie wiring modification confusion

Posted: Mon Nov 18, 2019 12:22 pm
by englishstiv
Oh , there have been a few,.........funny thing is ,they never seam to hang round long , after a) we start asking technical questions , and b) they realise WE (collectively ) know our stuff and thusly cannot be bullshitted
We have a certain Fin on here who often susses those wafflers out and a few others could be named from around the world - when they are here and about.... It is sometimes nice to sit back and see the arguments evolve. :banghead: