Foglight rewire guide for full control w/ OEM switch
Sep 4, 2016, 09:01 PM
#1
Foglight rewire guide for full control w/ OEM switch
There are already a few foglight-rewire how-to's on the forum, however none of them were exactly to my liking. What I wanted for my foglights was the following:
I'm happy to say that this method of rewiring checks all those boxes. Read on if you'd like your fogs to work like this too.
Parts needed:
- Schneider Electric/Magnecraft 711-type Relay **Discontinued; see below for possible replacement
- (Optional) Relay mount makes it easier to connect all your wiring to the new relay.
- Wire
- Tools for cutting/stripping/splicing wires
- Electrical tape/heatshrink wrap/whatever you want to cover your wire splices with
** The exact relay I used has been discontinued for a few years, but this part from McMaster-Carr appears to be equivalent: https://www.mcmaster.com/1358T13/
Their matching socket is here: https://www.mcmaster.com/1358T21/
Note that I haven't personally tried this McMaster-Carr relay, so I can't 100% guarantee it works. From comparing its specs with the one I have though, I don't see why it wouldn't work since the specs seem identical.
The relay is the key to this; it converts a momentary switch like our OEM foglight switch into a latching-type switch. Even better with this one is that it also maintains its state after it loses power. This means that if you had your fog lights off when you turned your car off, they'll still be off the next time you start it. If you had them on when you stopped the car, they'll turn back on the next time you start it.
Here's the wiring diagram, overlayed on top of the OEM wiring diagram (grayed-out parts won't be touched).
Figure 1:
Wiring the relay:
Figure 2:
- The 'B' pole just goes to a ground. There's a bolt very close by that you can use, just above the hole where the left screw of the dash trim goes.
- The 'A' pole goes to pin 1 (top wire) of the fog light switch
- The '6' pole has two wires going to it: one from a 12v power source (see figure 3 below), and one going to pin 2 of the fog light switch (second wire from the top)
- The '9' pole goes all the way to the engine bay, to the OEM fog light relay (A-06X). See figures 4, 5 and 6 below, and afterwards for more on how I did the wiring in the engine bay.
Figure 3, showing the fuse I used as a 12V power source. This fuse only gets power when the ignition is 'on' (not 'acc'). If for whatever reason you want to use the fogs with the key in 'acc' as well, you'll need a different fuse. This is in the fuse box under the steering wheel.
To route the wire from the relay to the engine bay, I passed through a grommet above the clutch pedal assembly which leads to the fender. You'll likely need to turn the steering wheel in order to be able to squeeze your hand in behind the fender liner to get the wire and route it to the engine bay.
Figures 4 and 5, showing where I routed the wire from the cabin to the engine bay.
Figure 6, showing the fog light relay in the engine bay junction box.
Wiring in the engine bay:
Just two things need to be done in the engine bay.
1. Pin 3 on the fog light relay needs to be grounded. Figure 8 below shows where I grounded it.
2. Pin 2 is where the wire coming from the cabin goes.
To do the wiring for this relay, you can take apart the junction box in order to get direct access to the wires under it, where you'll be able to cut and splice as needed. To open the relay box:
- Remove the covers on both relay boxes. (The square-ish one and the skinny one right next to the battery)
- Remove the 2 10mm bolts securing the relay boxes in place. One is barely visible in the bottom left corner of figure 6, and the other is at the opposite corner.
- Now, the skinny relay box needs to be removed before being able to get to the big one. On each long side of the skinny relay box, there are 3 small tabs in which you can stick a flat screwdriver to be able to separate it from the base of the relay box. You'll only be able to access 5, but this will be enough to partially separate the base from the box. You now need to release the 2 bigger tabs holding the small box to the big one, and you'll be able to start sliding the skinny box upwards. On my car the wires under the small box going into it had very little give in them; this is why the base needs to be separated; in order to allow the rest of the box to slide out from the clips holding it to the big one. As you slide the box out, you should be able to release the last small tab to completely separate it from the base, which will give you more leeway to get it out.
- With the small relay box separated from the big one, you can now reach the small tabs all around the big relay box that are holding the base in. When all tabs are released, you can tilt the relay box forward to see the horrible/wonderful jumble of wires underneath it. Refer to figure 7 below for the pinout of the fog light relay. As a reminder, the relay we need is A-06X, and the wires that need to be cut to be spliced elsewhere are 2 and 3. When you cut, make sure to leave yourself a long enough wire coming out of the base of the relay box to be able to strip the end and splice it into the wire from the cabin (for pin 2) or an extension to be able to ground it (pin 3).
Figure 7, showing the pinout for the relay box.
Figure 8, showing where I grounded pin 3 of the fog light relay.
With that done, you should be done! Enjoy!
- Retain the OEM switch
- Be able to turn the fogs on/off without having the low beams on
- Have the lights stay in the same state even after the car is turned off (for example, if the lights were on when I shut the car off, I want them to turn on again the next time I start it). Because I use the foglights as DRLs here in Canada, I want them on whenever I'm driving during the day, without having to remember to turn them on every time I start the car.
- Leverage as much of the OEM wiring circuit as possible
I'm happy to say that this method of rewiring checks all those boxes. Read on if you'd like your fogs to work like this too.
Parts needed:
- Schneider Electric/Magnecraft 711-type Relay **Discontinued; see below for possible replacement
- (Optional) Relay mount makes it easier to connect all your wiring to the new relay.
- Wire
- Tools for cutting/stripping/splicing wires
- Electrical tape/heatshrink wrap/whatever you want to cover your wire splices with
** The exact relay I used has been discontinued for a few years, but this part from McMaster-Carr appears to be equivalent: https://www.mcmaster.com/1358T13/
Their matching socket is here: https://www.mcmaster.com/1358T21/
Note that I haven't personally tried this McMaster-Carr relay, so I can't 100% guarantee it works. From comparing its specs with the one I have though, I don't see why it wouldn't work since the specs seem identical.
The relay is the key to this; it converts a momentary switch like our OEM foglight switch into a latching-type switch. Even better with this one is that it also maintains its state after it loses power. This means that if you had your fog lights off when you turned your car off, they'll still be off the next time you start it. If you had them on when you stopped the car, they'll turn back on the next time you start it.
Here's the wiring diagram, overlayed on top of the OEM wiring diagram (grayed-out parts won't be touched).
Figure 1:
Wiring the relay:
Figure 2:
- The 'B' pole just goes to a ground. There's a bolt very close by that you can use, just above the hole where the left screw of the dash trim goes.
- The 'A' pole goes to pin 1 (top wire) of the fog light switch
- The '6' pole has two wires going to it: one from a 12v power source (see figure 3 below), and one going to pin 2 of the fog light switch (second wire from the top)
- The '9' pole goes all the way to the engine bay, to the OEM fog light relay (A-06X). See figures 4, 5 and 6 below, and afterwards for more on how I did the wiring in the engine bay.
Figure 3, showing the fuse I used as a 12V power source. This fuse only gets power when the ignition is 'on' (not 'acc'). If for whatever reason you want to use the fogs with the key in 'acc' as well, you'll need a different fuse. This is in the fuse box under the steering wheel.
To route the wire from the relay to the engine bay, I passed through a grommet above the clutch pedal assembly which leads to the fender. You'll likely need to turn the steering wheel in order to be able to squeeze your hand in behind the fender liner to get the wire and route it to the engine bay.
Figures 4 and 5, showing where I routed the wire from the cabin to the engine bay.
Figure 6, showing the fog light relay in the engine bay junction box.
Wiring in the engine bay:
Just two things need to be done in the engine bay.
1. Pin 3 on the fog light relay needs to be grounded. Figure 8 below shows where I grounded it.
2. Pin 2 is where the wire coming from the cabin goes.
To do the wiring for this relay, you can take apart the junction box in order to get direct access to the wires under it, where you'll be able to cut and splice as needed. To open the relay box:
- Remove the covers on both relay boxes. (The square-ish one and the skinny one right next to the battery)
- Remove the 2 10mm bolts securing the relay boxes in place. One is barely visible in the bottom left corner of figure 6, and the other is at the opposite corner.
- Now, the skinny relay box needs to be removed before being able to get to the big one. On each long side of the skinny relay box, there are 3 small tabs in which you can stick a flat screwdriver to be able to separate it from the base of the relay box. You'll only be able to access 5, but this will be enough to partially separate the base from the box. You now need to release the 2 bigger tabs holding the small box to the big one, and you'll be able to start sliding the skinny box upwards. On my car the wires under the small box going into it had very little give in them; this is why the base needs to be separated; in order to allow the rest of the box to slide out from the clips holding it to the big one. As you slide the box out, you should be able to release the last small tab to completely separate it from the base, which will give you more leeway to get it out.
- With the small relay box separated from the big one, you can now reach the small tabs all around the big relay box that are holding the base in. When all tabs are released, you can tilt the relay box forward to see the horrible/wonderful jumble of wires underneath it. Refer to figure 7 below for the pinout of the fog light relay. As a reminder, the relay we need is A-06X, and the wires that need to be cut to be spliced elsewhere are 2 and 3. When you cut, make sure to leave yourself a long enough wire coming out of the base of the relay box to be able to strip the end and splice it into the wire from the cabin (for pin 2) or an extension to be able to ground it (pin 3).
Figure 7, showing the pinout for the relay box.
Figure 8, showing where I grounded pin 3 of the fog light relay.
With that done, you should be done! Enjoy!
Last edited by Raptord; Jan 8, 2021 at 07:44 AM.
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detroit pistins (Sep 11, 2016)
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Oct 27, 2018, 04:37 AM
#10
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Bump...I'm trying to wire my fogs and follow this exact setup. Unfortunately, the relay you have listed is discontinued. Do you have any other types of relays you could recommend? I'm not too good with electronics. Thanks!
Oct 27, 2018, 12:53 PM
#11
You can check this PDF from Schneider Electric which explains how the 711 relay I linked worked, to help find a replacement: https://www.serelays.com/library/section7/105A_755.pdf
Basically you should look for an impulse latching relay, ideally that also uses permanent magnet latching so that it remembers its position when you turn the car off.
Jul 18, 2020, 11:39 AM
#12
had similar problem due to broken ground from manifold to firewall. car would have a weak crank and sometimes wouldn't even crank. cleaning up the burnt fused ground wires sucked ***. this post helped me solve the problem, much thanks
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MIVEC-YEETS (Jan 16, 2022)
Jan 8, 2021, 07:41 AM
#13
As pointed out by enzone above, the relay I used at the time has been discontinued for some time. Until now, I wasn't aware of any equivalent replacements, but I believe I've now found one at McMaster-Carr:
https://www.mcmaster.com/1358T13/
And the socket: https://www.mcmaster.com/1358T21/
As a disclaimer, I haven't tested it so I can't be 100% sure it works the same as the one I'm using now, but based on the spec sheet, it seems it should work exactly the same.
https://www.mcmaster.com/1358T13/
And the socket: https://www.mcmaster.com/1358T21/
As a disclaimer, I haven't tested it so I can't be 100% sure it works the same as the one I'm using now, but based on the spec sheet, it seems it should work exactly the same.
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