[O-TownMDX]

I have not had the chance to try this. On the TL website they are doing it to their '02 TL's. I must warn you this is a lengthy, but very imformative post.

How to wire fog lights to come on with just the parking lights.
Okay, for anyone that wants to run their fog lights with just their parking lights on, I've figured out how to do it. I did it on my '02 TL-S and it works fine. I know some posted here before wanting to know *why* someone would want to do that (I believe in some states like CA it's illegal to run just fogs), but here in MA you can run just fogs and parking lights at dusk, in the rain, etc. Or if the fog is so thick that just fogs gives you better visibility you can run the fog/parking combo without low beams (even at night). This post may seem lengthy but I tried to be as explicit as possible. Maybe this can get added to the FAQ.
First my warning: Although is mod is 100% effective and safe to do, I absolve myself of all claims of damage to your vehicle should you not be able to complete this mod correctly (or you pound a couple 40s before trying it).

Time to complete: 20-30 minutes, even for a beginner
Tools needed: Short phillips-head screwdriver, small pair of scissors (or razor knife), some type of in-line electrical connector, crimping pliers for electrical connector

Background: Because laws vary from state to state, Acura must make sure that its lighting is 50-state compliant. So even though some states allow it, they must wire the car so the fog lights (a) cannot be operated independant of the lights, (b) cannot be operated with just the parking lights, and (c) cannot be operated when the high beams are on. This mod changes the fogs so they will now do (b) in addition to how they normally function.

What the mod does: When the fog light switch is pressed, the current wiring system has the first fog light relay (there are two--this one is in the passenger side footwell) check the position of the light stalk. If it is switched off or to parking lights, no power passes to the second relay which powers the fog lights. Once it is switched to low beams, power passes through the first relay which then in turn powers the underhood relay and sends the high voltage (20A) to the fogs and lights them. The mod rewires and fools the fog light switch into thinking the low beams are on when the light switch is moved to the parking light position.

Procedure:
1. Remove cover from driver's side fuse panel. This cover is the entire end-piece of the dash. You need to open the driver's door fully to properly access this panel. It is held in place only by pressure clips. Simply pull up and out at the very bottom to start the loosening process. Gently apply pressure to the side closest to the driver and the top and the whole cover will pop out. Notice there is a long ridge on the side closest to the firewall. Make sure that side goes in first when putting the cover back on.

2. Loosen left side of driver's underdash kick panel. Although you could remove this whole piece, you only have to loosen the left side near the fog light switch to do this mod. Looking in though the opening you just made with the cover removal, you should see two brass-looking phillips-head screws. One is close to the front of the dash, one is down behind some wires holding a long thin brace in place, closer to the firewall. This is the screw you need to remove. It is the *only* screw that holds the driver's side underdash kick panel in place. Once you've removed the screw, you can loosen the left portion of the underdash kick panel by gently pulling on the piece. There are two clips at the top front, close to the bottom of the gauge cluster. You pop these clips out and the left side will come away from the dash. *This is as far as you need to remove the underdash kick panel.*

3. Unplug wiring harness to dash light dimmer switch. This is a simple plug harness that is indexed so it only goes back one way--no need to remember how it went in. This gets the cables more free for the next step.

4. Remove the fog light switch from the dash. Easiest way is to reach in from the side and grab it gently from behind (sounds like some of my dates). Squeeze gently top and bottom and push forward (towards where driver sits). The switch should pop out and be hanging by its wiring harness. Unplug the wiring harness. Press the tab in on one side of the harness and pull gently out. Set the switch aside and push the wiring harness back through the opening and bring it out through the side so you can work on it easier.

5. Spice the wires. The wiring harness consists of an inline, 5-prong plug, which is connected by five 18-20 gauge wires that are individually exposed for about an inch and then are bunched together by some rubber conduit tubing. Take the scissors or razor knife and carefully cut open the tube to expose more of the wires. You need to cut back about two inches, because you're going to want about three inches of slack to work with. Once you've cut the tubing, fan all the wires flat. You have five wires going to the harness. They are:

1. White/Blue - Ground side of indicator light (green light that shows fogs are on)
2. Blue/Red - Power to passenger side footwell relay
3. White/Red - Power from headlight switch
4. Red/Black - Power from taillight relay
5. Red - Connection to dash light brightness controller

Wire number 4 provides power to the icon on the switch whenever the lights are on (parking lights/taillights are all on one circuit). Wire number 3 provides power through the fog switch *only* if it detects the headlight switch in the low-beam position. So what we do is splice wires 3 and 4 together, thereby bypassing the headlight switch altogether. Now, whenever the taillights have power, so will this leg of the switch and the fogs will come on when the switch is pressed.

You can use whatever means you wish to join wires 3 and 4 together. Just remember you *don't* want to cut them, just splice the two together. I highly recommend an inline automotive wiring splicer (the kind that looks like a double-barrel shotgun from the end). These types of splicers are meant to be slid on over an exisiting attached wire and a second wire's free end is slid into the other side of the connector. The connector is then crimped and the latch cover is closed. However, because both of these wires are connected at both ends, if you use this type of connector you will need to drill out or punch out the solid end of the connector so both sides are completely open on each end. Then simply slide the wires into the connector, crimp the metal blade down through the wires and snap the plastic retaining tab closed. If you're good with solder you can solder in a jumper between wires 3 and 4, but that makes the mod much more permanent. I strongly recommend a two-wire inline connector and crimp.

6. Reassemble the fog light switch. Take the wiring harness from the side and push it back through the hole in the dash where the switch goes. The wiring harness for the dash light dimmer control is sort of tied with this one so you have to make sure you keep them separate and only push the fog light harness through the hole. Snap the wiring harness onto the fog light switch (it can only go one way). Then gently push the fog light switch back into the dash opening (make sure it is right-side up--green light on top, icon on bottom).

7. Replug the wiring harness into the dash light dimmer switch. Self explanatory.

8. Reattach underdash kick panel by pushing gently in area of the clips until they snap into place (remember there are two at the top, just under the gauge cluster)

9. Replace the phillips screw in the brace for the dash panel.

10. Replace driver's side fuse panel cover. Remember to start it by inserting the side closest to the firewall first. It just snaps into place.

That's it--you're done. The only thing you've changed is now the fogs will come on whenever you have the light switch either in the parking light position or in the low beam position. NOTE: The fogs will *still* go off when you use high-beams so this mod will not cause trouble for those who live in a place where it is illegal to drive with high beams and fogs together. Making them come on *with* the high beams is a much more in-depth mod and will not be dealt with here. What's more, if your fogs are on and you shut off just the headlight switch, the fogs go off too (like the factory set-up). Remember it this way--whenever the taillights are on, the fogs can also be on (*except* for when high-beams are also on).

Whew! I know it seems like it is complicated, but this is a very easy mod. If you've crimped wires before in a car it's even easier. Most of you could do this in 20 minutes, no more than 30 minutes for a real beginner.

 

[Steve]

Thanks for your explaination. What is the way to wire the fogs so they are operated only by their switch? As in "A" of your post - "independant of the head lights". (and shut off if the car is shut off to avoid a dead battery).

We live in a rural area that (in the off season anyway) finds me quite often on road without other cars. Running with fogs AND high beams on is great - almost like day time! This can now be accomplised by manually holding the highs on while lows and fogs are on, a pain in the left hand.

Looking forward to your reply with wire crimpers in hand -

 

[taschroth]

Using Fogs as Daytime running lights...

Great find for the fog rewire, it sounds like you could put ignition power to the trigger wire instead and get the fogs to be available whenever the car is running.

I was able to get my fogs to come on with the ignition at about 1/2 brightness (6 volts) as daytime running lights and then go to full power whenever the headlights come on. A side effect is that the fogs stay on with the highbeams and if the car is running and if the headlights are on but the fog switch is off, they are still on the 1/2 power setting. (other words, if the igntion is on the fogs are on one way or the other)

Please don't ask for details on this mod is it was 8 months ago but basically I used 2 relays that created 2 separate fog circuits. One relay, activated by the ignition, shunts power to the fogs in series which effectively halves the voltage so they are running off 6 volts. This means they should not burn out much quicker even being on all the time. The other relay is activated by the headlight switch and takes out the 1st relay and let's a full 12volts go to the fogs.

The X's delivered in Canada would need dayime running lights by law but I can not find anyone to tell me how they do it. Anyones have a Canadian spec MDX that knows, pass it on.

 

[rroof]

Wow - great, detailed post! Thanks!

 

[rvehock]

Just finished re-wiring my fog lights so that they come on with my parking lights. The instuctions listed in the first post of this thread worked out great. Took me a total of 15 minutes, a great low-cost upgrade for sure:4:

 

[Gregc]

I hate to bring this up, but this Mod could cause very serious problems. Connecting Red/Black wire to the Wht/Red wire connects 2 different circuits fused by 2 different sized fuses. The fuse for the Red/Black wire is 15a fuse 10 (this is the fuse for most running lights and the Multiplex control unit) on the passenger's side. The fuse for Wht/Red is a 20a fuse 43 (this is the fuse for the right side headlamps). Adding these 2 values together brings you up to 35amps. That means when the headlights are on you have 2 paths to get 12volt power at a total of 35 amps. This could be very dangerous if a component shorted out or drew too much current. The wires could overheat and start a fire, or you could damage the Multiplex Controller. This mod would be better if you cut the Wht/Red wire and used one of the Scotch-lock connectors to connect the switch end of the Wht/Red wire with the Red/Blk wire. That would acomplish what you want without cross wiring the circuits. You would need to insulate the cut end of the Wht/Red wire. Should work fine that way. For those that have cross wired the circuits, simply cut the Wht/Red wire past your connection and insulate both sides and you should be good! Never just tie 2 circuits together, you are inviting trouble.


Greg in Atlanta

 

[Steve]

Perhaps you could revise the step by step mod instructions of the earlier post to allow those of us who are less talented to attemp this (with the most chance of success).

I don't understand why the car is not built so the fogs can be used without the lowbeams. Many other cars come that way.

Thanks, Steve

 

[Gregc]

Perhaps you could revise the step by step mod instructions of the earlier post to allow those of us who are less talented to attemp this (with the most chance of success).

I don't understand why the car is not built so the fogs can be used without the lowbeams. Many other cars come that way.

Thanks, Steve

The step number 5 needs to be changed.


5. Splice the wires. The wiring harness consists of an inline, 5-prong plug, which is connected by five 18-20 gauge wires that are individually exposed for about an inch and then are bunched together by some rubber conduit tubing. Take the scissors or razor knife and carefully cut open the tube to expose more of the wires. You need to cut back about two inches, because you're going to want about three inches of slack to work with. Once you've cut the tubing, fan all the wires flat. You have five wires going to the harness. They are:

1. White/Blue - Ground side of indicator light (green light that shows fogs are on)
2. Blue/Red - Power to passenger side footwell relay
3. White/Red - Power from headlight switch
4. Red/Black - Power from taillight relay
5. Red - Connection to dash light brightness controller

Wire number 4 provides power to the icon on the switch whenever the lights are on (parking lights/taillights are all on one circuit). Wire number 3 provides power through the fog switch *only* if it detects the headlight switch in the low-beam position. So what we do is splice wires 3 and 4 together, thereby bypassing the headlight switch altogether. Now, whenever the taillights have power, so will this leg of the switch and the fogs will come on when the switch is pressed.

You can use whatever means you wish to join wires 3 and 4 together. Just remember you do need to cut the White/Red (wire3) wire about 2 to 3 inches from the connector, on the switch side splice the White/Red wire to the Red/Black wire (wire4). I highly recommend an inline automotive wiring splicer (sometimes called a Scotch-lock connector). These types of splicers are meant to be slid on over an exisiting attached wire and a second wire's free end is slid into the other side of the connector. The connector is then crimped and the latch cover is closed. . Then simply slide the wires into the connector, crimp the metal blade down through the wires and snap the plastic retaining tab closed. If you're good with solder you can solder in a jumper between wires 3 and 4, but that makes the mod much more permanent. I strongly recommend a two-wire inline connector and crimp. Be sure to Tape up the exposed end of the White/Red wire (wire 3) that was cut. Also I included a picture of a Scotch-lock connector...Hope this helps and keeps everyone safe!



Greg in Atlanta

 

[Gregc]

For some reason the picture of a Scotch-lock did not show up!!! Let's try it again!!!

 

[rvehock]

The step number 5 needs to be changed.


5. Splice the wires. The wiring harness consists of an inline, 5-prong plug, which is connected by five 18-20 gauge wires that are individually exposed for about an inch and then are bunched together by some rubber conduit tubing. Take the scissors or razor knife and carefully cut open the tube to expose more of the wires. You need to cut back about two inches, because you're going to want about three inches of slack to work with. Once you've cut the tubing, fan all the wires flat. You have five wires going to the harness. They are:

1. White/Blue - Ground side of indicator light (green light that shows fogs are on)
2. Blue/Red - Power to passenger side footwell relay
3. White/Red - Power from headlight switch
4. Red/Black - Power from taillight relay
5. Red - Connection to dash light brightness controller

Wire number 4 provides power to the icon on the switch whenever the lights are on (parking lights/taillights are all on one circuit). Wire number 3 provides power through the fog switch *only* if it detects the headlight switch in the low-beam position. So what we do is splice wires 3 and 4 together, thereby bypassing the headlight switch altogether. Now, whenever the taillights have power, so will this leg of the switch and the fogs will come on when the switch is pressed.

You can use whatever means you wish to join wires 3 and 4 together. Just remember you do need to cut the White/Red (wire3) wire about 2 to 3 inches from the connector, on the switch side splice the White/Red wire to the Red/Black wire (wire4). I highly recommend an inline automotive wiring splicer (sometimes called a Scotch-lock connector). These types of splicers are meant to be slid on over an exisiting attached wire and a second wire's free end is slid into the other side of the connector. The connector is then crimped and the latch cover is closed. . Then simply slide the wires into the connector, crimp the metal blade down through the wires and snap the plastic retaining tab closed. If you're good with solder you can solder in a jumper between wires 3 and 4, but that makes the mod much more permanent. I strongly recommend a two-wire inline connector and crimp. Be sure to Tape up the exposed end of the White/Red wire (wire 3) that was cut. Also I included a picture of a Scotch-lock connector...Hope this helps and keeps everyone safe!

Greg in Atlanta

Greg,

Thanks for the 411, I will make the changes you suggested.

 

[rvehock]

Cut the red/white wire and all functions well, thanks for the information greg, I was unaware of any potential problems related to the original instructions from the TL website. I have also posted this information on the TL web forum so they can be aware of the potential wiring overload issue.

 

[HrdTsk]

Update for 2003

I tried this mod today with my 2003 Mdx Touring Nav. The color of the 5 wires seems to have changed. Mine has (top to bottom at the switch) :

White/Blue
Blue/Green
Red/Green
Red/Black
Red

Does anyone know which wires to splice to accomplish this mod for the 03?

 

[EXCALIBUR]

HrdTsk,

It seems like the logical decision would be to splice the Red/Green and Red/Black wires together. I followed the original instructions by O-TownMDX for my 2002 MDX and they worked fine. Go for it and see if it works. Since you are only using an inline splicer, there would not be any irreversible damage if it does not work. If all goes wrong, I shall alert the bomb squad and your next of kin. Good luck.

 

[HrdTsk]

Re-wire

Thanks

I wonder if anyone has the schematics or knows of a way to test with a voltage tester?

 

[PsychoKnight]

Don't Do It

Thanks

I wonder if anyone has the schematics or knows of a way to test with a voltage tester?

HrdTsk,

I've converted the wire colors from my 01 schematics to the 03 colors you provided, based on top to bottom harness positions.

wht/blu (heavy) = neg to combo switch for hi-bm cutout
blu/grn = pos to fog relay
red/grn (heavy) = pos from combo sw (20A)
red/blk = pos panel light circuit (15A)
red = neg to multiplex

The TL post mod calls for jumping the pos. panel light circuit to the pos. from the combo sw, that is, red/grn to red/blk.

I don't like this. You will notice that the red/blk will replace the red/grn, but the red/blk is much thinner than the red/grn. You will be taking a wire that is intended to support a .84 watt bulb (yes, less than 1 watt) to activate a high current solenoid relay switch, inducing a physical movement within the relay through an electro-mechanical motor (solenoid). Without testing through a micro-ammeter I have no idea how much power it takes to power the switch on this particular relay, but even if its just 200MA, that is still 3 times more than this wire was supposed to provide to the itty bitty indicator bulb. To figure the draw on this icon circuit, you would have to add up all the wattages for every single dash light, indicator light, and icon light which this circuit supports, then add a percentage for overload margin, then see if there is sufficient excess capacity to activate the fog relay, after you determine the average draw from the relay.

Plus, any electrical engineer will tell you;
Unless you know the entire scope of what you are dealing with (i.e. the total wattage/amperage suported by these circuits, both the icon light circuit and the fog relay circuit), you don't ever, ever, replace a wire with a thinner gauge wire - just as you would never replace a fuse with one of a higher capacity. You would be reducing your safety margin by an unknown degree.

I offer a friendly suggestion that you look for another way to power the fog relay besides sucking power from the delicate icon light.

P.S. Disclaimer:
I am 98% certain that I provided the correct wire codes, but without checking an 03 manual properly, it is possible to connect a high amperage 12 volt positive directly to the negative input of the multiplex controller, resulting in the destruction of your driver's multiplex unit (expensive computer module).

 

[DaleB]

Re: Re: Re-wire

just as you would never replace a fuse with one of a lower capacity. You would be reducing your safety margin by an unknown degree.

I think you meant don't replace a fuse with one of 'higher' capacity (it will blow later, or TOO late).



But very good advice and consideration.

 

[PsychoKnight]

Re: Re: Re: Re-wire

I think you meant don't replace a fuse with one of 'higher' capacity (it will blow later, or TOO late).



But very good advice and consideration.

Damn, your fast! Not 2 minutes later and I get a correction from Ol' Dale.

Thanks.

 

[EXCALIBUR]

TheyCallMeBruce,

Hmmmm. Something to think about. Neverthless, splicing the White/Red and Red/Black wires together on my 2002 MDX worked for me without any adverse effects. This mod. allowed me to run my foglights with my parking lights. YMMV.

 

[DaleB]

Re: Re: Re: Re: Re-wire

Damn, your fast! Not 2 minutes later and I get a correction from Ol' Dale.

Thanks.

Ha, ha! No problem my pleasure. Great advice you offer in your usual thoroughness. Reminds me of the Six P's!


Prior Planning Prevents Pi** Poor Performance

Good to remember before undertaking any task.

 

[HrdTsk]

Thanks Bruce

Given my limited technical ability, I think I will pass on the mod as suggested in this post. Could you propose an alternative within the scope of an adverage person? Please feel free to say no if that is what you think.