North American Turbocoupe Organization



Fog lights wiring question...
Kuch Offline
Senior Member
#1
I would like to change my wiring for the fog/driving lights to be able to come on with the parking lights and not just the head lights. I will be adding headlight relays this spring so is this doable while I do that? Thanks for any info.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, BBK AFPR, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
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Jeff K Offline
Administrator
#2
Pretty easy (at least for someone like me who spent their carrier as a physicist and electrical engineer) ..... Assuming you want the fogs to come on with only the park lights and go off when headlights are switched on.

You will need 2 12 V relays. One must be a 5 terminal with a normally closed (NC) set of contacts and one 4 terminal with just the normally open (NO) set .of contacts that can handle 10 A minimum. Standard automotive 30 A or 40 A relays would be fine,

Tap into the park light circuit and run it to the coil on the relay with the NO contacts. Other coil terminal to ground. Run a wire from the headlight circuit to the relay with the NC contacts coil, and other coil terminal to ground.

On the relay with the coil connected to the park circuit run a fused circuit from +12V hot at all times to one of the NO relay terminals. The other NO relay terminal goes to one of the NC terminals on the relay connected to the headlight circuit. The other NC terminal goes to the fog lights.

Theory of operation: With park lights on, relay powered by the park circuit turns on, current flows from 12 V hot at all times, thru the NC terminals of the relay connected to the headlights to the fogs and turns them on. When headlights are switched on, the relay connected to the headlight circuit energizes opening the NC terminals and turning off the fogs. Dash switch will still work normally to turn the fogs on/off.

.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Kuch Offline
Senior Member
#3
Jeff, thanks for the detailed response, I appreciate it. I would still like them to be on with the headlights as well, just being able to have them on with the parking lights too. So how could I still use the factory switch for turning on like factory, but also on with the parking lights as well. If that makes sense.
1988 Turbo Coupe, Black/Black, 5 Speed, Moonroof,  T3/T4 50 trim, ported E6, 255LPH, BBK AFPR, 3" DP dual 2.5" w Hooker Maxflows, MGW shifter, K&N, Gillis valve, RR cam, Koni's
1964 Ford Galaxie 500XL, 390 6V, 4 Speed, Vast and fast
1960 Ford Starliner, 292 Y Block, 3 Speed, slow and low
Reply

Jeff K Offline
Administrator
#4
Even easier if you want them on with the headlights also........ Only need one 4 terminal relay with the coil wired between the park lights hot side and ground. No need for the 2nd relay wired to the headlight circuit.

I have may fogs (converted to LED units that are BRIGHT BRIGHT) wired as DRLs. The fogs are on at half brightness whenever the key is in RUN, and turn off when the headlights are on. Headlights are also LED. Fogs go to full brightness when turned on with the dash switch, and also turn on at full brightness when the high beams are turned on. Fogs on with high beams is illegal in most, if not all states but I dont care. I like to be able to see at night.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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