Any electricians in the house familiar with 12v relays?
I know what a relay does, and I know how to hook one up, but what I don't know is where to get them and what kind I would need for my application.
My new vehicle has fog lights. I would like to add an additional pair of HELLA or similar (PIAA maybe?) lights in the center of the front bumper. To power these, I will go directly to the car's battery. To switch them on/off I will connect a relay's "low side" to the fog lights and the "high side" to the new lights. The lights will either be 55w or 100w a piece.
I guess if I really, really wanted to, I could run a switch on the relay's low side up and inside the car so I could control them independently of the fog lights.
What I don't want to do is modify the car in any way that can't be undone. I don't want a bunch of janked-up wire/birds nested/taped crap when you open the hood. So I'm trying to do this in the least intrusive manner possible.
I assume that the "low side" of a relay has a pretty low nominal draw? Any ideas on what the latent draw for the "low side" of a relay that could handle this application would be?
Thanks guys.
Not a electrician but have always hooked up the power wire to the starter motor + ... auto elec bloke told me it's better that way... and keeps more wires out of sight too
I believe the input on most relays is 5 volts? All the input does is complete the circuit from power source to accessory, so it's not huge at all. Your best bet might be to just put them on an independent switch. Otherwise, you'd have to splice into the existing fogs/light stalk.
If you go that route, do as Janx said: pull switch power from the starter motor so that you can't accidentally leave them on and kill your battery. Were it me, I would do as follows:
Switch input from starter + (can be found in fuse box under the hood).
Switch output to relay "low" input.
Relay "high" input from battery.
Relay ground.
Relay output to fogs.
All of that would be adding wiring without touching any of the stock components. If you're careful with it, you can easily hide everything behind the bumper cover and run the switch wiring through the firewall into the cabin following your stock wires.
Quote from: JAS6377 on December 11, 2014, 10:02:04 PM
I believe the input on most relays is 5 volts? All the input does is complete the circuit from power source to accessory, so it's not huge at all. Your best bet might be to just put them on an independent switch. Otherwise, you'd have to splice into the existing fogs/light stalk.
If you go that route, do as Janx said: pull switch power from the starter motor so that you can't accidentally leave them on and kill your battery. Were it me, I would do as follows:
Switch input from starter + (can be found in fuse box under the hood).
Switch output to relay "low" input.
Relay "high" input from battery.
Relay ground.
Relay output to fogs.
All of that would be adding wiring without touching any of the stock components. If you're careful with it, you can easily hide everything behind the bumper cover and run the switch wiring through the firewall into the cabin following your stock wires.
Ah, okay, good point.
I thought for sure I'd be able to find a 12v relay high AND low side. Been looking but it's hard to know what I'm looking at without holding it in my hand. I might take a look at a local shop or NAPA to see what they might be able to come up with.
Also, here's what I was thinking I would do:
The fog-lights have their own, separate switch already. I could run the "low" side of the relay to the fuse box where the fuse for the fog lights is located. Tap in the "low" side of the relay there, so I don't have to booger up the wiring for the fog lights or anything at all.
I've done this for radios and other accessory installs before; you just remove the fuse, fold the bare wire over the blade, and then shove it back into the fuse block. It's a little rigged-up but it works just fine - did this for the tach install on my Ranger 10 years ago and it's worked ever since. Of course I would add another fuse to the low-side of the relay, just in case.
As far as the "high" side of the relay, I don't see why it would be an issue to run directly to the battery? Not that I will or won't do it that way, but I'm just curious. The fog lights automatically turn off when you turn the key off, which would turn off the relay, and would prevent me from accidentally leaving the lights on.
You're dead on. I didn't realize your fogs were already on their own switch. Probably because my car didn't actually come equipped with them lol. But yes. Low input from that fuse to trigger the relay, high input from battery, ground to ground (duh), and output to extra fogs. As extra protection, I always add inline fuses to relays. It may not be necessary, but it's peace of mind. The only issue I see is that the fog fuse may be always powered, depending on where in the circuit it is. You can try that wiring setup and see how it goes. I'd just do a quick mock-up first, then go from there.
Quote from: JAS6377 on December 13, 2014, 06:01:36 PM
You're dead on. I didn't realize your fogs were already on their own switch. Probably because my car didn't actually come equipped with them lol. But yes. Low input from that fuse to trigger the relay, high input from battery, ground to ground (duh), and output to extra fogs. As extra protection, I always add inline fuses to relays. It may not be necessary, but it's peace of mind. The only issue I see is that the fog fuse may be always powered, depending on where in the circuit it is. You can try that wiring setup and see how it goes. I'd just do a quick mock-up first, then go from there.
All well and good but...I still don't have a relay to use, which was the point of this thread - LOL!
You can buy fitting kits over here with everything you need included.
http://www.amazon.co.uk/Universal-Relay-Wiring-Switch-Driving/dp/B008CFL8EW (http://www.amazon.co.uk/Universal-Relay-Wiring-Switch-Driving/dp/B008CFL8EW)
Someone must sell them over there :dunno_black:
Be careful where you pick the feeds up from, CANBUS systems don't like being messed around with :thumb:
Sorry lol. I got a 30 amp automotive relay from Amazon, and a 10 amp inline fuse from my local Radio Shack. A standard 4 pin relay should do just fine.
As long as you have it set up for off road only or a switch so you dont blind oncoming traffic, youre golden. Ive used a power distribution block which was fused and a guarded toggle switch
Okay, let me backtrack just a bit here...
I actually need a suggestion on what kind of relay I should be using. I don't know a lot about them. I just need a 12v "high" and "low" side...but not sure if there might be a specific type that might suit my needs best.
https://www.google.com/search?q=12+volt+automotive+relay+wiring+diagram&biw=1366&bih=635&tbm=isch&imgil=wGKJKoVUxPUJ6M%253A%253BIZk0ESLfKREfRM%253Bhttp%25253A%25252F%25252Fforum.ih8mud.com%25252Fthreads%25252Fconverter-radio-install-in-bj71.818882%25252F&source=iu&pf=m&fir=wGKJKoVUxPUJ6M%253A%252CIZk0ESLfKREfRM%252C_&usg=__AxaVjp7FVHHEza-woy3TM85taw8%3D&ved=0CDEQyjc&ei=Wr-QVIS3ONTYoATq3ICIAw#facrc=_&imgdii=_&imgrc=wGKJKoVUxPUJ6M%253A%3BUh5_rLr9XqLI7M%3Bhttp%253A%252F%252Fwww.mp3car.com%252Fvbulletin%252Fimagehosting%252F12527647e9129233622.bmp%3Bhttp%253A%252F%252Fwww.mp3car.com%252Fvbulletin%252Fthe-faq-emporium%252F117895-faq-relays-how-they-work-and-how-to-wire-it-up.html%3B453%3B385
A 3 pole relay? I take it you want to have 2 light levels available
Quote from: yamahonkawazuki on December 24, 2014, 02:50:13 PM
A 3 pole relay? I take it you want to have 2 light levels available
I dunno where 3 pole came from. But, no, I don't need 2 light levels.
I think I'll shelve this idea for now. The first thing I need to do is replace the 1980's stock head unit. It doesn't even have a play/pause function which aggravates the hell out of me.
My mistake on the brainfart :oops: