100W aux lights, simple noob wiring question.

[Randy88FJ62]

Picked up some old pro comp 100 watt, 8 amp draw driving lights for $20. Is there anything special to wiring these puppies up? I was going to run accessory wires to the battery and run an inline switch to turn them on and off.

Why do some light kits come with relays and fuses? Is there anything I need to know so i don't wreck the lights or my truck's electrical system?

Are two of these lights going to draw more than my car can handle with stock alternator?

Looking to wire these up tonight in case I go to Calico for the weekend.

Thanks.

 

[90FJ62]

You need a relay so that you are not pulling the current through the switch for the lights. You should be able to get everything you need form autozone or similar store.
There are a few different ways you can wire up the lights and many diagrams have been put into threads here.

Dave

 

[Randy88FJ62]

You need a relay so that you are not pulling the current through the switch for the lights. You should be able to get everything you need form autozone or similar store.
There are a few different ways you can wire up the lights and many diagrams have been put into threads here.

Dave

Thanks, I'll do some searching on wiring diagrams.

 

[Randy88FJ62]

Found some explanations and it doesn't look too difficult. I have a question regarding running an inline fuse. Should I be running a fuse in between the battery and the relay to protect it from frying in case of a power surge? And if so, what amperage fuse should I be using?

 

[djawahir]

I would run a fuse between the 12V and the relay if I was doing a fresh wiring job. But, that's just me. I think the relay would blow if there was a short in the wire anyways. But, double the protection isn't necessarily a bad thing, right?

 

[lovetoski]

And if so, what amperage fuse should I be using?

20 or 25 amp fuse.

P=VI
P = Power(watts)
V = volts
I = Current(amps)

200watts = 12VX??

200/12 = 16.666amps.

Interesting side note...
200/12 = 16.666amps
200/14.4 = 13.88amps

An properly functioning alternator will put out 14.4 volts (+/- .3). Higher voltage will reduce the amp load on the system. Also, light output from halogen bulb is very dependant on voltage. Using a relay + the correct guage wiring reduces voltage drop, which in turn makes for brighter lights and less strain on the whole electrical system.

 

[Randy88FJ62]

I picked up 12 gage wire for the install. I think it will be plenty big enough to get the voltage to the lights.

Thanks for the answer Lovetoski. I took circuit theory in college and all we did was theory. Look where that got me now. Classroom is useless without hands on experience.

Looks like I have everything I need for the job. Thanks everyone for the quick answers.

 

[Randy88FJ62]

I wired everything up and it doesn't work. My guess is that the switch needs to have the ground / accessory wires switched as the truck is "negatively grounded" as some have said. Or the relay I used is not correct.

Please take a look at the diagram below and let me know what I am missing.

The relay says 12V 40A and in between those two numbers is the number 240 circled.

 

[90FJ62]

Randy
I would pull the 12v hot wire for the switch from a different leg than the one going to the lights. I did this in a friends truck last week and used a switched 12 volt wire from his dash. This made it so that he could turn the lights on only when the key was in aux or on. and yes you will need a ground for the switch relay and lights. I will look at the relays i have for my lights in a sec and see what they say. Other than that looks like a good diagram.

dave

 

[Randy88FJ62]

You have a good point regarding the lights being on only when in ign or acc.

I believe the problem is the pin designations for the Bosch relay. I keep finding conflicting information regarding which pin does what.

Right now I have it set up as:
Pin 85 Ground
Pin 86 Switch
Pin 87 12V from battery
Pin 30 To Lights

Is there a mistake in this assumption?

 

[ntsqd]

Can you get someone to turn on the switch while you have a finger on the relay? You should be able to feel the relay vibrate slightly with turned on or off. Knowing that will narrow down which side the fault is on.

 

[ntsqd]

I doubt that it should make any difference, but you might try reversing your 30 & 87 wires. The 85 & 86 terminals should be interchangeable unless your relay is diode protected, then it *might* matter.

I usually wire them:
30: Battery 12 VDC
87/87A: Load (which depends on what)
85 or 86: Battery 12VDC
86 or 85 (whatever remains): To switch; switch to ground.

That isn't the common way to do it and ignores the key on/off thing (don't want that for myself), though it works well it is contrary to what you have.

 

[augirthedude]

You have a good point regarding the lights being on only when in ign or acc.

I believe the problem is the pin designations for the Bosch relay. I keep finding conflicting information regarding which pin does what.

Right now I have it set up as:
Pin 85 Ground
Pin 86 Switch
Pin 87 12V from battery
Pin 30 To Lights

Is there a mistake in this assumption?

Relays check out this web page for the definative answer

 

[Randy88FJ62]

I burnt the 30A fuse. Why would it be eating fuses?

 

[Randy88FJ62]

I talked to the Bosch guy and he said that 85 / 86 and 87 / 30 can be interchanged without a problem. So I feel better on how I wired the relay.

I used a multimeter and checked out the wiring. I'm getting 12V at the relay from the battery. So I'm back onto how I'm frying fuses.

 

[ntsqd]

The linked page mentions that relays with protection diodes across the 85 and 86 terminals are polarity sensitive. Wired backwards results in a short to ground. Try reversing those two wires and see what happens.

 

[Randy88FJ62]

The linked page mentions that relays with protection diodes across the 85 and 86 terminals are polarity sensitive. Wired backwards results in a short to ground. Try reversing those two wires and see what happens.

The Bosch rep I talked to said they could be switched but you could be right. I'm heading out for the weekend, hiking in Mammoth. I'll check back on Sunday night.

If anyone has any other ideas on why I'm burning up fuses, please lt me know.

Thanks.

 

[ntsqd]

With both the unprotected relays and the resistor protected relays the polarity should not matter and the Bosch rep would be 100% correct.
As pointed out by the above link a diode protected relay having the wrong polarity causes a short to ground. Which would blow any fuse.

 

[Randy88FJ62]

No matter which way I hook up the 2 wires to the relay (85 and 86) I get the fuses to burn. Any other ideas?

 

[Dynosoar]

Randy, Follow the diagram below.

Dynosoar