johnnyd

No, I’m not actually running this, but it a basic schematic and does work.

Incorrect, the second relay only has four connections. The coil is powered by the 12v+ feed from the BCM (Body Control Module) to one side of the coil; the other side of the coil is to ground, it is completely isolated from pins 87a and 30.

You are correct, it may be risky depending on a Diode to prevent backflow of current to the BCM despite the fact that most Diodes failers tend to cause an open, like blown fuse condition. The Diode isn’t really necessary in the circuit because 87 and 87a should never bond together. That said, a circuit without the need of a Diode would be a plus.

A better solution may be: (The 12v+ high amperage source is completly isolated from the Factory BCM.) NOTE: Although not shown in the diagram, this diagram is intended to be used with a Bosch relay that includes suppression on the coil to prevent inductive kickback, Bosch makes several with a resistor or quenching diode - no need to install on the outside. The relays with a diode suppressor will have polarity sensitive coil connections.

JK-Ford

I looked at this point again and I still see the same thing. Or maybe we just have a diferent approache. What I see is that your reverse circuit is connected to 87 of the first relay and feeds through that relay via terminal 30 to the second relay at terminal 85, actavating the coil of the second relay. ince you show the diode at terminals 87 and 87a of the first relay, you are effectivly bypassing that protection device. I was unaware of the existance of this type of protection. I will research this information so that I may expand my skills in this area. Once again I would like to apoligize to jmat1980 for hyjacking this thread.

JonathanL83

Wow.. ok, so this is the thread I was looking for apparently.
I have two 55watt backup lights that I want to function as so:
When I shift into reverse the fog AND stock lights always light up.
When I flick a switch on the dash (could be driving down the highway or parked in gear) the fog lights light up (not the stock lights).
I'm just confusing myself looking at everybody's different schematics for this setup; which will work best for my function? Will one 5-prong relay do the job? Do I need a diode for back-flow protection? If this really is such a hassle I'll just resort to a toggle switch and be done with it.
Thanks guys, I'm very appreciative that you all share this info!

whpony96

Post number 31 is the correct way to wire the reverse lights to work WITH a optional switch on the dash as well..The only thing I would add just to be safe is Diode on pin 85 where the 12+ supply voltage is coming from. This will give a bit of added protection for the factory electrical system from a back flow of voltage from the collapsing magnetic field off the coil when the relay is disengaged. A diode is basically a voltage one way valve. Voltage will only pass in one direction thru it. If you reverse the diode (or install it incorrectly) the only thing that will happen is nothing...Because it stops the voltage from passing thru it.

JonathanL83

Thanks, today I was able to purchase two relays that both have the coil between 85 & 86 (Hooray!). I'm using the attached diagram.
Is it safe to power both -a lighted switch and the power to the relay- directly from the auxiliary cigarette lighter?
Or do I have to buy a couple ATM fuse taps and go the heated-seat route?

jmat1980

I have mine running off just one relay and its been working fine for several months. Im no electrician, but the 2 relays + diode, may be overkill, but maybe its better to be safe than sorry

JonathanL83

EDIT: lights all in working order, just as I wanted, I'll post a short install in another thread.
My last post covered why I don't need the diode; the relays I bought have the coil built-in (between prongs 85 and 86). I understand the need for both relays in my situation; one is used strictly to trip the fog lights when the Jeep is in reverse, while the other relay allows for me to trip the switch at any given time while parked or driving. If I could have purchased a 5-prong (dual-87 style) relay I would have, but non could be found locally and I wanted to make this a weekend DIY.
Today I purchased an ATM add-a-fuse at Pep-Boys ($10 ripoff! Advance Auto sells the Bussman brand for closer to $6, but alas AA was sold-out). I'll plug that into the fuse box (the heated seat plugs -M8 or M9- will do). I've already run a large gauge wire (12 or 14) through the foam insulation (right below the corner of the passenger-side windshield) to the relays that will be mounted by the passenger's foot rest area.
After I complete this light project I'll write up a full install, hopefully making it easier for the next guy like me..

jmat1980

Ok, I got ya...I used the Relay with 87 and 87A, now I know why you needed 2

viper02

[QUOTE=JonathanL83;1179308]EDIT: lights all in working order, just as I ....
... the relays I bought have the coil built-in (between prongs 85 and 86)....

Can you let us know the specifics of these relays? Where did you get them, part number, price, etc?????

whpony96

You will be just fine using the acc outlet.. but if it was me to be safe I would run to the battery (or use the heated seat plugs) just to isolate you reverse lights from the jeeps electrical system.