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DIY: (w/pictures) How to wire foglight switch from interior to engine bay

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Old 10-21-11, 02:24 AM   #1
KahnBB6
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Default DIY: (w/pictures) How to wire foglight switch from interior to engine bay

When I did my 97+ foglight conversion I got as far as installing the housings and wiring up the relay harness but when it came time to install an interior switch there was no information available. I got the impression that it was common to just wire fog lights to turn on with the main headlights or parking lights automatically on 92-94 SC's.

That wasn't good enough for me. I needed a switch on the dash. Getting a 1995+ column stalk surround installed was going to be a pain so I decided to install my own. Here's how you can too:

No one seemed to know where the trigger and relay wires could be routed to the interior floorboard until StiCk3 (thank you again!) suggested a much better alternative to the steering column boot or the engine wiring harness plug on the passenger side.

THE SWITCH

The location I used to mount is the interior panel with the instrument dimmer switch. If you pull this out, you'll see that just to the right on the inside is a blank spot for another OEM switch/indicator. I don't know what Toyota intended for this but I can't even find examples of its use in Soarers. It's the perfect location for a black switch.

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I found this switch at Pep Boys. It was the only decent looking thing they had that might have worked. They have several versions with different indicator lights in red, amber and blue. I chose amber.

Click the image to open in full size.

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1.) Take a small drill bit and carefully mark and align where you want to make your hole. I removed the switch housings after having done this and drilled from the inside out. Then take a 15/16" drill bit (or whichever bit size your switch specifies) and carefully drill from the inside. When you're finished, take a Dremel with a light bristle (nylon fiber) wheel and get rid of any excess.

Click the image to open in full size.

Click the image to open in full size.

2.) For this switch I had to notch one side very gently to allow it to snap in place. I haven't shown pictures but you will also need to dremel down whatever areas of the switch conflict with the blank inner OEM housing. I preferred to score up the switch instead of dremeling anything else on the Lexus panel. Either way works.

Click the image to open in full size.

3.) Now connect your wires using crimp terminal connectors found at Radio Shack. I used three separate spools of 18 gauge wire in green (ground), black (relay connection) and red (trigger; in this writeup I would be using the parking lights).

Click the image to open in full size.

This particular switch was made for a flat surface and in a Lexus SC there is hardly a flat surface anywhere on the car to mount it. Considering that what Calty intended in 1991, that's actually pretty cool. From a profile it doesn't look good but consider that most of the time the angle of view (driver and passenger) isn't going to reveal this tiny gap.

Click the image to open in full size.

And here is how it should look when completed. It's not a factory switch but it's passable, clean and accessible in an intuitive location for a fog light switch.

Click the image to open in full size.

THE WIRING

1.) Jack up your car on the driver's side front (be safe about this! Use a jackstand!), remove the wheel (21mm socket, 101 ft-lbs each lug) and set it aside. Now you must remove the upper splash shield. There are MANY screws and bolts. Be sure to keep track of them. Before you can do this, however, you must carefully(!) remove the lip strip from the outer edge of the wheel well. Those screws are tiny!

Click the image to open in full size.

2.) Now we can see two very critical areas: a passthrough to the engine bay through the fender and a sealed rubber grommet duct that leads directly into the interior floorboard near the fuse box.

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This closeup is of the grommet. Take a 10mm socket and take out the two bolts. They are long, so be patient. This will help you later to align wires or a clothes hanger feeder.

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3.) Next, there will be a thin layer of electrical tape sealing the end tube of the grommet. peel this off and keep your own roll of electrical tape handy. You'll need it later.

Click the image to open in full size.

4.) Now we'll go back to the interior. I already wired up my foglight switch wiring in this picture (the black, red and green wires that are zip-tied). A ground (green wire in my harness) is available near the fuse box in an OEM location. Use that, then secure your trigger and relay wires (here they are red and black respectively) and get a long, straight coat hanger end.

Click the image to open in full size.

5.) Go back to the wheel well. Take the coat hanger end and feed it through the small tube end of the grommet. Bend it a little to get it to angle correctly and try helping it through with your fingers under the unbolted area of the grommet. Now you should have the straight hanger fed through a bit. It is far easier to feed it this way than the other way around, which might poke a hole in your grommet.

6.) Back into the interior, tie your red and black wires to the coat hanger and prepare to feed it through the grommet. It's a tight fit but it WILL work.

OPTIONAL: at an electronics supply store, get some narrow shrink wrap tubing and slide that over your wires to protect them. This will usually be heat shrink tubing and works best with a heat gun.

7.) Feed the red and black wires through the grommet and leave just a little slack in the interior. You never know what you may need to splice in the future.

8.) Now take your electrical tape and cover up the grommet end just the way the OEM tape was laid on. It shouldn't take much.

9.) Finally, feed the lines through the engine compartment access hole. You can now connect your relay terminal and trigger signal as described in O.L.T.'s 92-94 foglight conversion thread and you will have an interior switch wired into a clean location!

10.) Replace the wheel well splash shield, outer lip, all bolts and your front wheel (when a couple of bolts are threaded securely enough, lower the car from the floor jack enough to give the wheel traction. Then tighten all the bolts to 101 ft-lbs in a star pattern. Do a final check. Now lower the car and you're done!

And the final product. I haven't pictured it but I can now have the fog lights off with the parking lights on with the flip of a switch on the dash

Click the image to open in full size.
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Last edited by KahnBB6; 10-21-11 at 03:32 AM..
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Old 10-21-11, 05:00 AM   #2
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Late night Diy ftw!
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Old 10-21-11, 05:19 AM   #3
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I like the creativeness of the switch location, good stuff.
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Old 10-21-11, 02:13 PM   #4
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Thanks guys! Hope it helps someone!
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Old 10-21-11, 03:20 PM   #5
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Not being an a$$, but this way is easier as I've done it already; post #22

http://www.clublexus.com/forums/sc-4...ght-mod-2.html

You didn't have to go through all that trouble..
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Old 10-22-11, 01:54 AM   #6
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It's cool Philip! My DIY was a bit of trouble but only because Toyota made it so hard to gain firewall access in these cars.

I just looked at post #22 but it doesn't really explain what is being done. You're saying the switch wires for the trigger and relay signals never needed to go through the firewall? I know it's also possible to get a trigger signal from one of the fuse connections under the dash but a wire does have to reach the relay on the fog harness in the front of the car if the intention is to have a dash mounted switch.
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Old 10-22-11, 11:34 AM   #7
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I just realized that you have a '93, and the thread I posted says '95-'96, so I'm not really sure what's the difference in terms of wiring over the years. Well, what it is is, it by-passes the relay for the fog lamps so you have full control of it and not depend on the park light for you to turn it on/off. If you follow post #1 of that thread you can turn on/off the fog lamps even if the park lights are turned completely off, post #22 allows you to turn on/off the fog lights independently when the park lights are turned on.
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Old 02-06-12, 04:54 PM   #8
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i actually got the 95 column switch i wanna use that to switch on the lights but i see no write ups.
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Old 02-06-12, 06:52 PM   #9
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I like seeing these types of threads on here. Looks good and your mission was accomplished. Well done.
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Old 02-06-12, 06:54 PM   #10
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Very nicely done!
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Old 02-06-12, 07:20 PM   #11
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thank you for taking time out of your day to do a DIY for CL.
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Old 02-06-12, 10:15 PM   #12
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I have the same switch, wired at the same spot. Good going.
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Old 08-08-14, 08:41 AM   #13
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Thanks for linking me here Kahn, I'll be doing this when my 3k HIDS get in.
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Old 08-08-14, 09:43 AM   #14
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I have a 1995, if I bought a 97 bumper would i need to do any of this?
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Old 08-08-14, 04:25 PM   #15
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Quote:
Originally Posted by Kris9884 View Post
Thanks for linking me here Kahn, I'll be doing this when my 3k HIDS get in.
No problem. Hope it helps!

Quote:
Originally Posted by SoarerXavi View Post
I have a 1995, if I bought a 97 bumper would i need to do any of this?
SoarerXavi, you actually shouldn't have to do this if you have a 1995. Unless I am mistaken 1995 was the first year (USA models) for factory fog lamps instead of the 92-94 cornering lamps. Your wiring should support 35w fog bulbs already and you *should* have a fog lamp switch on your lighting control stalk on the left of the steering column.

So apart from the 97-00 bumper, grill, foglight housings, foglight connectors and electrodes... no, you shouldn't need to make a custom foglight harness or wire in an aftermarket interior switch. Your Lexus should have all that built-in as a 1995+.

In your case you will need to splice the new 97+ foglight electrodes (in those new plastic connectors) into your 1995 foglight wiring and that's it. I recommend solder covered in heat-shrink tubing but you can use crimps from radio shack too.
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