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Dash light hot

The dash light hot is teh same circuit the runs most of the parking lights and other "lights on" circuits. Some are through relays, others are direct.
That circuit should have no trouble running one more relay.

Both my Pilot and CR-V are wired that way with the factory fuse, and no problems.
 

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Re: Dash light hot

N_Jay said:
The dash light hot is teh same circuit the runs most of the parking lights and other "lights on" circuits. Some are through relays, others are direct.
That circuit should have no trouble running one more relay.

Both my Pilot and CR-V are wired that way with the factory fuse, and no problems.
Yes, I count 26 categories of items powered by this circuit, more items than any other fuse in the entire vehicle (albeit individually very low-powered items). And it may not be all that frequently that you would press on the brake pedal at night, while the glove box, both vanity mirrors, and the optional cigarette lighter is in the opened position and . . .

I never said the circuit couldn't handle the additional draw. What I am saying is:

1. Unless you make precise calculations, you don't know - you are making assumptions.

2. No custom automotive electronics installer, or regional power grid EE, will say it is advisable to replace the function of a power line with a lower capacity unit without knowing the above.

3. You won't find any literature, instructions, handbooks, technical references, in print or online that supports this type of blind modification.

So it begs the question;
why would Honda/Acura use a thicker gauge wire for the relay signal than the icon light, at higher expense?
A) they want to waste money
B) they want to make life harder for the wiring vendor by specifying differing gauge wires on the same harness without cause
C) they don't know how to add up the power consumption on this circuit and were just guessing that a thicker wire was better
D) they looked at the numbers and decided it was quantifiably necessary regardless of the inconvenience of implementing non-uniform wire gauges, at the expense of heavier gauge wiring.

Several people have performed this modification without any negative results. Therefore, it must be deemed safe and appropriate by current engineering standards (no, I'm not an elect. engineer and I don't know crap about designing circuits).

George Burns is puffing on his 4,937th cigar on his 100th birthday with a showgirl in his lap and says "Na, smoking doesn't hurt. Look at me!"

If anybody wants to perform this specific modification really badly, go ahead. Just know that . . . you don't really know!

Good luck. I'm a risk taker too. Alone, I didn't even know if I would make it back from the Arctic coast to the wife waiting at Dawson.
 

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TheyCallMeBruce,

Your point has been so noted. I sense your motivation is to be the voice of conservatism. The fact is many MDX owners, myself included, have performed this simple "no-cost" mod. with no adverse results. I love to be able to drive with the parking lights and foglights. So, for you brave souls willing to "throw caution to the wind", I say "step up to the plate and go for it.":29:
 

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EXCALIBUR said:
TheyCallMeBruce,

That being said, I sense your motivation is to be the voice of conservatism.
Uh, sort of, but not quite.
You would not be able to call the 200 hours or so of modifications I have performed on my MDX to be exactly "conservative." In addition to several other areas, I have modified the lighting system extensively. My fog modification was also near to zero cost, but I went through the effort to choose connection points which I felt were appropriate and I used wires which were either equal to or thicker than those I bypassed. Contrary to conservatism, in order to do a job right sometimes, you have to make seriously radical modifications. Pursuing such, I have torn out and replaced entire subsystems (such as when I rigged a previous car to roll all windows and moonroof down or up with the alarm remote, back in the late 80's before any kits were avail). If I am uncertain how my actions will affect the original system, I will disconnect the original and create a redundant system. Or else, do nothing at all.
But I'm glad everything worked out for you. Thanks for your response.
 

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Great information, but......

For those of us that really need fog lights w/o headlights for real fog, how do the stock fog light perform? My experience has been that just about every factory installed fog light is crap. Is the MDX foglight sufficient, after your mod to run w/o headlights, for real fog, or am I better going back to my PIAA dealer and wiring them in with parking lights only?
 

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TheyCallMeBruce said:


I have modified the lighting system extensively. My fog modification was also near to zero cost, but I went through the effort to choose connection points which I felt were appropriate and I used wires which were either equal to or thicker than those I bypassed.
Curious how you went about this... I assume you also provided a different power source to the fog relay? In perusing the schematics and wiring diagrams, I didn't see a particularly convenient location for this - unlike for my Audi, where it can be done in the fuse box itself.

I've not been entranced with the trigger-by-illumination circuit, but haven't seen a particularly nice way to get the same function. I would be interested in how you solved this problem.

Thanks,
Richard
 

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solomon said:


Curious how you went about this... I assume you also provided a different power source to the fog relay? In perusing the schematics and wiring diagrams, I didn't see a particularly convenient location for this - unlike for my Audi, where it can be done in the fuse box itself.

I've not been entranced with the trigger-by-illumination circuit, but haven't seen a particularly nice way to get the same function. I would be interested in how you solved this problem.

Thanks,
Richard
I do not have my fogs tied into the tail lights. They are wired like factory DRLs of most makes. What I did will only confuse you if you want the fogs to work automatically in the combo light intermediate position.

I've only just started to look at the problem this way, and I'm not fully confident, but this is the direction I am working it, if I were to run the fogs in the intermediate position:
Based on '01 manual color codes
1. Jump the wht/red from the fog switch to IG2 yel ignition wire using an integrated fuse piece loaded with a 3amp ATC.

This allows power to the fog switch whenever the ignition is on. The fogs will not activate by themselves because the permanent ground will be re-routed to a switched source in the next step.

2. At the combo switch harness I would pull out the wht/blu pin (all harnesses Ihave seen on the MDX so far are quick release designs, just pop open the harness and pull gently with needle nose, you can insert just as easily) and attach it to the red/yel pinout.

This keeps the fogs from coming on except when the headlight switch is in the parking light or headlight position.



These mods will not defeat the fog switch, you can turn it on and off as before, with the addition of turning them on with only the parking lights. Why go through all the trouble? My idea is to avoid replacing a wire with a thinner gauge, and pull the additional draw (a very small draw) from the very heavy IG2 wire instead. Yes, I'm still sucking power from an un-intended source, but the difference is that I would be using the absolute thickest wire in the cabin compared the the absolute thinnest wire. I would also be redundantly providing a fused-controlled power source with a larger gauge wire rather than replacing a wire with a thinner piece.

Again, I haven't done this, I went with an entirely different arrangement. Somebody speak up if you see any weaknesses in this setup.
 

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Everyone relax

The relay takes fractions of an amp.
Even 24 guage wire will carry well over 1 amp.

To make everyone happy, pick up the same circuit, just get it off a lead running to a larger load, and therefore running in a thicker wire.
The same color code is typically the same circuit. (But test to be sure)
 

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Re: Everyone relax

N_Jay said:
The relay takes fractions of an amp.
Even 24 guage wire will carry well over 1 amp.

To make everyone happy, pick up the same circuit, just get it off a lead running to a larger load, and therefore running in a thicker wire.
The same color code is typically the same circuit. (But test to be sure)
Sounds good to me.:D
 

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Re: Everyone relax

N_Jay said:
The relay takes fractions of an amp.
Even 24 guage wire will carry well over 1 amp.

To make everyone happy, pick up the same circuit, just get it off a lead running to a larger load, and therefore running in a thicker wire.
The same color code is typically the same circuit. (But test to be sure)
Sorry

What exactly do you mean with regard to the mod?

Do you have access to the 2003 schematics? Does anyone?

Sorry, with my level of expertise, I need the cookbook approach.
 

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Re: Re: Everyone relax

HrdTsk said:


Sorry

What exactly do you mean with regard to the mod?

Do you have access to the 2003 schematics? Does anyone?

Sorry, with my level of expertise, I need the cookbook approach.
Come on guys. It looks like HrdTsk might be back in on the rewiring foglights mod. Let's talk some plain english and K.I.S.S.:1zhelp:
 

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'03 fog light schematic

Maybe this will help someone.
 

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Colors Correct

Yes, when I took off the kick panel and inspected the fog light switch on the 03 MDX, I found top to bottom:

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

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Re: '03 fog light schematic

catzx6 said:
Maybe this will help someone.
Also, may I ask where did you get this schematic?
 

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where did you get this schematic?
Pg. 22-104 of the '03 Service Manual. ;)
 

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Re: Everyone relax

N_Jay said:

Even 24 guage wire will carry well over 1 amp.
Uh, where did you get this particular figure? And for what length of wire? Just curious. Thanks.
 

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Ampacity

There are lots of ampacity tables available.
A google search will fine enough to drive you crazy (as they all say different things).
Ampacity has more to do with acceptable voltage drop, and temperature rise than what the wire will carry before failure.
For the current levels and lengths we are talking about voltage drop is almost irrelevent.
 

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Re: Ampacity

N_Jay said:
There are lots of ampacity tables available.
A google search will fine enough to drive you crazy (as they all say different things).
Yes, they all have differing results. This is why I ask. The parameters of what is considered acceptable is an extremely important criterion.

Which chart did you use?

Have you ever have tried to power a 12VDC, 1 amp motor with 24 ga wire? You're telling me the voltage drop is neglible and the temperature rise is insignificant?

Now you have me really intrigued. Thanks if you have the time to provide the specific information of how you arrived at the 24ga/1amp specification.
 
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