I’m preparing to install a pair of driving lights on my 96 Ranger. I have some KC lights that are either 130 or 150 watts ea. I want to use Ford parts where possible / reasonable, namely the Ford Fog light switch and a small Ford relay & fuse box (I have both). I do not have enough of the factory wiring in the truck to utilize for this application.

I prefer to be safe in my install and will be using the switch to ground activate the relay. I think the wiring to the relay should be as follows:
Cab ground using the Black wire from Ford Sw to . . .
Ford Fog switch using the Bl/Bk wire (through the firewall) to . . .
Relay (#??) in relay box

Assuming the lights are the higher 150 watts each that calculates out to 12.5 amps each and 25 amps total going through the relay. The relay is a 4 pin (that’s how the Ford relay box I got is made).

So my questions are
1. Which relay pole do I run the ground switch wire to?
2. What amp rating should the relay be? Is 30 amps enough?

Then, the relay box will have 2 fuses (1 for each light) which will also be in the relay box. I can use either 15 or 20 amp fuses there. Then run the wiring to the lights.

Thank you for your input.

 

I thought I would get at least a little input on this. So I’ll bump this to see what input I can get.

 

Sorry missed it when first posted

Yes, ground activation from cab switch is best, that is what Ford does with their switch and relay
Yes, 30 or 40 amp 12v relay, that's pretty standard

This is a Micro relay diagram: http://www.gtsparkplugs.com/images/m...lay-wiring.jpg

This is a Mini relay diagram, most common: http://www.gtsparkplugs.com/images/m...ode-wiring.jpg

Pins/slot number in these diagrams is an industry standard, Ford uses 1 to 5 but doesn't always use the same 1 to 5, lol, so confusing

85 and 86 are the "activation" connections for the relay, if one is 12v and the other Ground then relay activates(closes), there is no polarity, so either can be 12v and the other Ground, doesn't matter
This is the 12volt rating for a relay

30 and 87 are the "load" connections, in this case Driving light's 12volts and amps pass thru these connections, these have the AMP rating, 30 or 40 amps
Also no polarity here, 30 or 87 can have the 12volts all the time, and when relay "closes" the "other one" gets that 12volts

87a can be there or not, doesn't matter for this use, but it is used in some circuits, AC circuit usually has a WOT(wide open throttle) relay, for this, 87a has 12v for AC compressor clutch which is hooked to 30, so when AC is on the 12v passes to AC Clutch from 87a to 30, relay is OFF
When computer "sees" WOT it turns ON this relay which cuts power to AC clutch giving engine MAX power for acceleration or passing, then when foot comes off the gas pedal AC come back on
This is used because relay doesn't have to be on full time for AC, just a better setup

So for your wiring you will hook up your FUSED 12volt power to 30 AND lets say 86, so both have power all the time OR key on power if you use another relay for that

Then Driving lights would be hooked to 87, and lights would be grounded

Then 1 wire from 85 to cab light switch, and switch is grounded in the cab, switch can have an LED that comes on when relay is grounded, via that same ground wire to relay


If you want you can hijack a key on source in the engine bay, like EVAP or EGR solenoid, they both have key on power only, and use that for 86 in this example, so no driving lights with key off
Or you can use parking light 12volt wire(brown wire in engine bay) for 86's 12v, so driving lights could only be used if parking lights/head lights were on

The 85 to 86 relay coil only has a 0.5amp current draw so will not overload any circuit in the vehicle


1996 fog light diagram below
For the fog light relay 2 would be our 85, the ground, and 5 would be the 12v for relay coil, 86

1 would be 12volt OUT to driving lights, 30
3 would be fused 12v IN 87

The LED in Fords switch is powered by fog lights being on, so you would need a second wire thru firewall to use that feature

 

relay wiring diagram.

150 watt ÷ 12 volts = 12.5 amps per light
2 lights = 25 amps
So, the lights will pull 25 amps
The relay can handle the load. But it would be better to overbuild the circuit. A relay with a higher rating. And... use a fuse as close to the power source as possible so you don't burn your truck down. Hope this helps