Wiring a relay for aux lights - HELP!!!!

SavageUrge · **Posted:** Mon Oct 19, 2009 8:55 pm

Does anyone have a straightforward diagram for wiring auxiliary lights through a 12V Bosch style 5-pin relay? I'm a complete idiot when it comes to electrical work and I'm pulling my hair out here!!

I'm hooking up auxiliary lights to the back to come on with the reverse lights and I'm using the trailer wiring to tap into. The last two attempts at wiring it failed for whatever reason. I used two different diagrams but neither of them worked. I need to know what wire is which in the trailer harness I think, but I can't find that online either. I just noticed that the relay I originally wired has different colored wires than the new one. I know I'm supposed to go by the pole and not the wire color, but it seems strange. Please help! Thanks in advance!

Diggerfreek · **Posted:** Mon Oct 19, 2009 10:37 pm

Ready

You want to tap your back up light power wire and run that to terminal 86 on the relay and then ground terminal 85. This is the switch part of the relay... then you want your fresh 12v B+ wire to go the 30 and wire your lights to 87a if the relay is normally open or 87 it it is normally closed...

If you need more help, e mail me and I will draw you a picture

BugginKJ · **Joined:** Mon Jul 06, 2009 7:35 pm **Posts:** 4576

Diggerfreek wrote:

Ready

You want to tap your back up light power wire and run that to terminal 86 on the relay and then ground terminal 85. This is the switch part of the relay... then you want your fresh 12v B+ wire to go the 30 and wire your lights to 87a if the relay is normally open or 87 it it is normally closed...

If you need more help, e mail me and I will draw you a picture

Holy crap all that great info stuffed behind those buldging eyes :shock:

Impressive man very impressive :lol:

Whats the crayon drawing look like? :lol:

Diggerfreek · **Posted:** Tue Oct 20, 2009 1:06 am

I'll have it in the morning

Diggerfreek · **Posted:** Tue Oct 20, 2009 2:15 pm

BugginKJ · **Joined:** Mon Jul 06, 2009 7:35 pm **Posts:** 4576

Diggerfreek · **Posted:** Tue Oct 20, 2009 4:21 pm

Have I said how much I suck @ MS Paint :lol:

SavageUrge · **Posted:** Tue Oct 20, 2009 6:07 pm

Wow, thanks for the help! Every diagram I've found on line says to use 87 and not 87A. I wonder if that's the problem because I think everything else is wired as you stated.

Diggerfreek · **Posted:** Tue Oct 20, 2009 6:15 pm

it all depends on how the relay is built.. If I saw the ISO picture on it, I could tell you. It is going to be built 2 ways, either 30 and 87 will be connected when power IS NOT applied to 86..... or either 30 and 87A will be connected when power IS NOT applied to 86

SavageUrge · **Posted:** Wed Oct 21, 2009 11:25 am

Thanks Diggerfreek - Some questions: What is B+ ? Is it Backup positive? Also, when you say the backup power wire, do you mean the wire from the backup light switch to the 7-pin trailer hookup (Brown/Green) or the power to the trailer hookup 12V supply (Yellow)? Sorry for sounding like an idiot but, well, I am when it comes to this stuff Again, thanks for the help! :roll:

Diggerfreek · **Posted:** Wed Oct 21, 2009 11:31 am

SavageUrge wrote:

Thanks Diggerfreek - Some questions: What is B+ ? Is it Backup positive? Also, when you say the backup power wire, do you mean the wire from the backup light switch to the 7-pin trailer hookup (Brown/Green) or the power to the trailer hookup 12V supply (Yellow)? Sorry for sounding like an idiot but, well, I am when it comes to this stuff Again, thanks for the help! :roll:

B+ is the ISO term for Battery power. Take you power for your lights off of the yellow wire if it is "live" all of the time and connect that to 30. Than take and connect to the brown/green (back up terminal) and run that wire to 86...

NO stupid question can be ever asked

I would rather have some one ask 100 question than not to ask and then blow something up....

Boiler · **Posted:** Wed Oct 21, 2009 11:52 am

Relays all have different wiring diagrams. We'd have to know the exact one to really tell you how to wire it accurately. Here you see a screenshot of a catalog page that shows:

1) some relays using 87a being a completed circuit when off, and 87 is completed when on (see bottom left relay)
2) other relays both 87a and 87 are completed when on (see bottom right relay)

Either way, 87 should always be completed when you energize the relay. 87a can vary depending on the relay.

I used the type where 87a and 87 did the same thing, and I wired pairs of lights on each relay, with one light's + going to 87 and the other light's + going to 87a.

If you don't know the wiring diagram, I'd go from your switch to 86, ground 85, run your fused battery positive to 30, and run 87 to your lights, then ground your lights. Your relay probably has the wiring diagram stamped on it though, if you want to make a decision to use 87a or not.

Diggerfreek · **Posted:** Wed Oct 21, 2009 1:12 pm

Nice find

SavageUrge · **Posted:** Wed Oct 21, 2009 4:11 pm

This is the relay I have:

Boiler · **Posted:** Wed Oct 21, 2009 5:13 pm

87 should go to the lights then.

Wiring diagrams are typically drawn in the unenergized state. So the solenoid hasn't shifted the contacts yet, as drawn.

Wiring a relay for aux lights - HELP!!!!

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