will this be safe on my car/fog lights

LtDavis said:

I'd like to do the fix shown at the Corral to my car but I still want the fog lights to automatically turn off when the high beams come on just like the factory setup is (also required by law in Pennsylvania) I don't know jack about wiring, so what would I do different in the wiring to make the fogs work like that?

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One thing to consider: It's also often illegal to have driving lights on without headlights. If this is so, you could simply install the Corral relay and leave the fog light switch's power source alone. The circuit would function as OEM, except you'd have a relay to protect the circuit from overloading.

Now if you want to have something else, but still want the fogs to shut down with the high beams................

One method:

Get an SPDT relay. You can think of this as splicing this relay into the wire that goes from the fog light switch to the relay (you could do this on the load side too, but I like switching the control side of the circuit). As far as splicing into the wiring from the Corral write-up, you will only deal with the wire that goes from the fog-light-switch output to the relay (you're basically cutting it and putting a relay in the middle of it. You don't actually need to cut the wire, but that's how to think of it in terms of circuit interruption). Wire it as follows:

30: Goes to the wire from the fog light switch. This used to go from the switch to the Corral relay.

87A (make sure you use the Normally Closed terminal, which is 87A, not 87): this goes to the Corral's relay where the fog light wire used to connect with the Corral method.

Those above connections are how the relay is spliced into the 'middle' of that one wire.

Now you connect 85 to ground.

And 86 gets spliced into the wire for the high beams. Just Tee into the brights circuit and run a leg of power to this terminal. It can be small gauge wire (a la 18 AWG).

What's happening: Your fogs are on. With this new relay, 30 and 87A are connected at rest (which for relay #2 is when the brights are off), so it's like this new relay is not even there. When the new relay sees highbeam voltage, it energizes the new relay, which takes power away from the Corral relay input, shutting the fog lights off.

Seems like it should work fine to me, and it's close to how I've seen some OEM circuits in other cars wired. If anyone sees a typo, please let me know.

Good luck.

bobbyd said:

jrich what does #85,86, and 87 represent? i think #30 is the 30amp fuse no?

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30 is a relay terminal, not the fuse. JRichker used a 20 amp fuse (Total Watts/Volts = Amps, to decide your power requirements. Rememeber total watts is for two bulbs)

On a SPST relay, the coil is comprised of 85 and 86. When one has power and the other has ground, the relay connects 87 (normally open) to 30 (common).

In JRichker's nice diagram, the curly cue represents the coil. When the coil is energized, the relay energizes and 30 and 87 connect up. If you're using an SPDT relay, at rest, 30 has continuity with 87A.


This is the conventional nomenclature. You can wire these dippy relays with the control and load sides backwards (i.e. connect power to 85, ground to 86. And battery power to 87 and have the output be 30. I HATE it when people do this. It is unnecessary and just leads to confusion). WIth higher end relays, you cannot wire them up backwards, so I always do it the same. Plus it's easier to chase wires if certain assumptions can be made.