RobDef90 Posted July 12, 2007 Share Posted July 12, 2007 Hey, after some questions i realised i am not as 'savvy' as i thought i was. Im after wiring four spots to my roof rack (55w each), spoke to auto elec today and he said i needed two relays so two pairs of lights not one quad.. Therefore does someone have,or can soemone quickly draw a basic diagram for me, 4 spots/2 relays/ one switch....thanks for any help Rob Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted July 12, 2007 Share Posted July 12, 2007 four lights @ 55w each = 220W. 220/12 = 18.3 A which is a bit close for a 20A relay, a 30A relay would be fine though. Either source a 30A relay, or use two 20A relays. The wiring remains essential the same, just in duplicate. the two low-current switching wires will just go to the one switch. Diagram to follow. Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted July 12, 2007 Share Posted July 12, 2007 Here's the diagram for two relays and four lights, also showing how you could use an on-off-on switch as suggested in your other thread. Quote Link to comment Share on other sites More sharing options...
DSN Posted July 12, 2007 Share Posted July 12, 2007 If for a roof rack, I don't think it is legal for them to come on with full beam so the double switch route is not truly legal. I might be wrong but think that is the case. Lorries get away with it because their high level spots are in front of the front wheels. Cheers, Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted July 12, 2007 Share Posted July 12, 2007 Also, i've not shown a dash tell-tale, which should be wired in to the same switching feed that goes to the relays. Quote Link to comment Share on other sites More sharing options...
RobDef90 Posted July 12, 2007 Author Share Posted July 12, 2007 Hey landymanluke, that is great!! Thanks..quick question, i had a 30A relay anyways, then the auto elec advised me to use two. I have bouight them both now, so should i use the two 30A relays or just stick with one for sake of ease....thanks...Rob Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted July 12, 2007 Share Posted July 12, 2007 It's up to you, a 30A relay will be up to it, there's no particular reason to use two. I have two, simply so i can switch inside and outside pairs, as they have different lenses on them. As long as the relay is suitably rated i see no other (simple) reason to use two. Make sure you use suitable fuses (10A) and the proper sized wiring. Quote Link to comment Share on other sites More sharing options...
RobDef90 Posted July 13, 2007 Author Share Posted July 13, 2007 Hey, back again, if i use one 30a relay for the four 55w spots, what size cable will i need to the lights? i assum if i use two seperate relays the wire would not have to be as thick....thanks Quote Link to comment Share on other sites More sharing options...
LandyManLuke Posted July 13, 2007 Share Posted July 13, 2007 We've already worked out that the four lights will be drawing 18.3A, so you need a cable capable of 20A plus. 2.5mm^2 is suitable for that current draw, however 4mm^2 will give less voltage drop over the length of the wire and is a better choice. If using two relays, you could run two 1.5mm^2 wires, or better, two 2.5mm^2 wires, to avoid as much voltage drop. Remember to run a decent earth back to the battery too. There's no harm in using bigger cable, there are a lot of downsides to using cable that's too small- higher resistance means dimmer lights, and warm cables. Given the choice, always go up in cable size, rather than down. Quote Link to comment Share on other sites More sharing options...
RobDef90 Posted July 13, 2007 Author Share Posted July 13, 2007 Thanks a lot, you have been an invaluable source... i will give it a go and try not to melt anything ....thanks...Rob Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.