Subaru_dude Posted January 14, 2008 Share Posted January 14, 2008 I'm trying to hook up fog lights on the roof of my EA82 but I can't figure out whether or not I really need a relay. It's going to have a dash mounted switch and will work independently from the headlights. Quote Link to comment Share on other sites More sharing options...
Durania Posted January 14, 2008 Share Posted January 14, 2008 It would be a better install if it did. The guy I got my BRAT off of ran the fog lights through the fuse box and wrapped the wire around a fuse. It would make things less dangerous if your alternator ever surged like my hatch's did. I ran my CB to the fuse box and alternator surged it caught the wiring on fire and gave me first degree burns on hand, not a good way to spend a day off from school. Quote Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted January 14, 2008 Share Posted January 14, 2008 I'm trying to hook up fog lights on the roof of my EA82 but I can't figure out whether or not I really need a relay. It's going to have a dash mounted switch and will work independently from the headlights. If you use the right size wire, right size fuse, and right amperage of switch, you can probably get away without using a relay. But if you know how to install and use a relay, I recommend it. Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 14, 2008 Share Posted January 14, 2008 I'm trying to hook up fog lights on the roof of my EA82 but I can't figure out whether or not I really need a relay. It's going to have a dash mounted switch and will work independently from the headlights. Hmmm... $3.00 for a brand new relay, $???? To replace your vehicle when it burns down due to a wiring short? I run relays on all my additional lights... Consider it cheap insurance! Quote Link to comment Share on other sites More sharing options...
[HTi]Johnson Posted January 14, 2008 Share Posted January 14, 2008 Hmmm... $3.00 for a brand new relay, $???? To replace your vehicle when it burns down due to a wiring short?I run relays on all my additional lights... Consider it cheap insurance! Very good point. I don't look at it as burning down, I look at it as weight reduction. Quote Link to comment Share on other sites More sharing options...
Skip Posted January 14, 2008 Share Posted January 14, 2008 coBob the relay will not prevent the burn down the fuse is what protects this from occuring I also recco a relay and fuses for all switched aux circuits drawing over several amps. see Daeron's excellent write up (link below) for a better understanding of relays and why/how to use them.. I also recco you bookmark this post http://www.ultimatesubaru.org/forum/showthread.php?t=73825&highlight=relay Quote Link to comment Share on other sites More sharing options...
MilesFox Posted January 14, 2008 Share Posted January 14, 2008 with my experiences some of the cheaper swithces will melt inside and lose a terminal. i would run a relay for that. otherwise use a nice heavy duty metal switch. you can take off power from the spare slot on the fuse link block Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 14, 2008 Share Posted January 14, 2008 cobcob the relay will not prevent the burn downthe fuse is what protects this from occuring True... That said, 90% of the switches that come with the lighting kits that you get at Wal Mart etc. are far too light duty to handle the DC arc that will pop between contacts when the switch is thrown. If the contacts get worn to a point that the spark is large enough then you have potential for the switch housing etc. to melt and catch alight. Seen it before and it's not pretty. Admittedly that was in a situation where there were a LOT of switching cycles on that switch each day but no fuse will help you out if that happens... The only switch that I would run in place of a relay is from an industrial control unit and is good for 130amps @ 220v... the contacts in that are pure beefcake... Quote Link to comment Share on other sites More sharing options...
Skip Posted January 14, 2008 Share Posted January 14, 2008 "If the contacts get worn to a point that the spark is large enough then you have potential for the switch housing etc. to melt and catch alight." If you say so sir, I believe it, as I have now "read it on the internet" Suffice it to say use your head. use a relay and fuse the systems properly. Quote Link to comment Share on other sites More sharing options...
Subaru_dude Posted January 14, 2008 Author Share Posted January 14, 2008 Ok, after reading all of your thoughts I decided to drop by my old work place and got a relay and a fuse for free. Now my next question. What gauge wiring should I use? I have 16 and 10 gauge. I was thinking bigger is better but I could be wrong I suppose? Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 14, 2008 Share Posted January 14, 2008 If you say so sir, I believe it, as I have now "read it on the internet" It's not terribly common but it happened on a road grader that came into the auto electrician shop I worked at in Australia. Cheap switch running 4 driving lights, lots of on/off cycles each 'day' (it was mostly run at night) Always better to be safe than sorry eh? Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 15, 2008 Share Posted January 15, 2008 You are correct in thinking that the larger wire will be better since it will carry more current and have less voltage drop than a smaller wire. The 16 gauge will work for doing both the switch/relay control and power to the lights though I would tend to use 14 ga. for the power to the lights. The 10 gauge will also work but that is a lot of overkill. Whatever you choose to use for this just be sure to protect the wiring with about a 15 amp fuse placed close to the power source. Quote Link to comment Share on other sites More sharing options...
Subaru_dude Posted January 15, 2008 Author Share Posted January 15, 2008 The relay I got already has some wires attached to it, but the wire that goes to the lights is attached to the middle 87A instead of the 87 on the outside... from what I understand the 87A constantly has power going to it? So I should use the 87 to go to my fog lights, right? Lemme just tell you what I understand and you guys can tell me if I'm right. Power comes in through the 30, goes to the lights out of the 87 (or the 87A if that's OK) The other 2 go to the ground and switch. Is that right? Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 15, 2008 Share Posted January 15, 2008 IIRC the 87 and 87A have different "normal" states... the outer one (87 I think) is normally off (switch off, no power at 87) 87A is normally on (switch off, power at 87A) Quote Link to comment Share on other sites More sharing options...
Skip Posted January 15, 2008 Share Posted January 15, 2008 Yes, you sound correct if the switch has battery power fed to it. Many thanks to Daeron from the link I guess you choose to not look at Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 15, 2008 Share Posted January 15, 2008 Looking at the drawing, it states that both 87 and 87A go to the lights and are tied to the common 30 when the relay is on. I don't know if this is really correct or not but a simple check with a ohmmeter tied between 30 and the other two points will show if it is. Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 15, 2008 Share Posted January 15, 2008 Looking at the drawing, it states that both 87 and 87A go to the lights and are tied to the common 30 when the relay is on. I don't know if this is really correct or not but a simple check with a ohmmeter tied between 30 and the other two points will show if it is. Googled "relay basics" http://www.teamrocs.com/technical/pages/relay_basics.htm "87 and 87a are the two contacts to which 30 will connect. If the coil is not activated, 30 will always be connected to 87a. Think of that pin as "87, always connected". When current is applied to the coil, 30 is connected to 87. 87 and 87a are never connected to each other." Quote Link to comment Share on other sites More sharing options...
Subaru_dude Posted January 15, 2008 Author Share Posted January 15, 2008 Why would I have BOTH 87A and 87 supplying my fogs? I would have one fog running off 87A (which always has current if I understand correctly) and one running off 87 which only has current when the switch is flipped. Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 15, 2008 Share Posted January 15, 2008 Why would I have BOTH 87A and 87 supplying my fogs? I would have one fog running off 87A (which always has current if I understand correctly) and one running off 87 which only has current when the switch is flipped. That diagram is incorrect in the labelling... it should read EITHER 87 OR 87A go to your lights. You will run both lights off one terminal. If you got a set of fogs with a wiring harness included one of the wires should have a large terminal on one end that allows you to plug both positive leads from your lights into it Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 15, 2008 Share Posted January 15, 2008 Good research on the relay Cobcob. From what you say then, I agree that the lights should be tied to 87 (the normally open contact) of the relay. The other contact, 87A would be the normally closed contact and just left open. Pin 30 is the common contact that has power tied to it. The common connection simply moves between these two points when relay is either off or on. Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 15, 2008 Share Posted January 15, 2008 Good research on the relay Cobcob. From what you say then, I agree that the lights should be tied to 87 (the normally open contact) of the relay. The other contact, 87A would be the normally closed contact and just left open. Pin 30 is the common contact that has power tied to it. The common connection simply moves between these two points when relay is either off or on. Correct, you realistically can wire your lights to whichever you chose... if you're installing a seperate switch for the lights then the only difference it will make is what position the switch is in when the lights are on... If you're like me and have more than one set of additional lights then you might not want to pop the dash panel off AGAIN when you test things and realize that one switch is up and the other down when the 2 sets of lights are on... simply switch the light connection from 87 to 87A and your switch positions will match up and look pretty Quote Link to comment Share on other sites More sharing options...
Cougar Posted January 15, 2008 Share Posted January 15, 2008 You can use either 87 or 87A but normally you would want the relay to be turned on to turn on the lights. It wouldn't be conventional for the relay to be turned on so the lights would be off. This would also mean there would have to be cutoff switch to the main power to the lights since power would be applied to them while the car is off. Pin 87 should normally go to the lights. Quote Link to comment Share on other sites More sharing options...
cobcob Posted January 15, 2008 Share Posted January 15, 2008 True nuff... if your lights are wired to a circuit that is normally off when the key is off. I have all of my lights wired direct off the battery so I CAN run them when the key is off if the need arises (not for long admittedly, I can put a hurting on the battery real quick with all my stuff lit up) but you never know what you might need to do in case of an emergency Quote Link to comment Share on other sites More sharing options...
daeron Posted January 16, 2008 Share Posted January 16, 2008 Congratulations USMB!!! You caught me. My HybridZ friends jumped on that inaccuracy as soon as i published that drawring over there. It took "us folk" over here six months to finally call me out, and make me get off my lazy butt. I am editing the image to reflect the info I now know to be true; namely, that post 87A outputs power when the relay is turned OFF. My apologies for my misconception, but SINCERE apologies for my laziness in not fixing that six months ago when I was first schooled on this skip, thx for the heads up. Quote Link to comment Share on other sites More sharing options...
Subaru_dude Posted February 8, 2008 Author Share Posted February 8, 2008 Completely forgot to show pics. http://i136.photobucket.com/albums/q200/SMASHmySOOByDONTya/DSC_0077.jpg Quote Link to comment Share on other sites More sharing options...
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