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My '02 has the factory option fog lights and as far as I can tell, the fog lights can only be turned on when the headlights is on. Also if both of them are on, and you turn the headlights off, the fog lights will turn off too.


BUT if you turn the truck off, the fog lights switch will reset. This mean that everytime I start my truck, I have to manually turn the fog lights on too. Kind of annoying. I like it when I have both headlights and fog lights on when driving in the dark ... seems to have better coverage.


So, before I tear the truck apart, I'd like to know if there is a way to make the fog switch stop from resetting itself everytime the truck is shut off? I am not sure if the fog light switch is computer or relay operated, but just want to know if it is do-able, and if so, how? Thanks!
 

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On my 03 the Fog Lights come on when the button is pressed and then only when the Low Beams are on - they go off when the High Beams come on. I was looking at the schematics in the Helms manual recently and all the lights (Hi/Lo/Fog) are controlled by the BCM (Body Control Module) so it's the BCM that resets the Fog lights when you shut down. I built a new headlight/fog light harness with some relays, diodes, 10 gauge wire and switches that allow both head lights and the fog lights to be on at the same time but I haven't had time to install it. If ever get it installed I'll post the details. You can also accomplish this using some diodes (wired OR) on the BCM (coil) side of the headlight/foglight relays. Another option is to use the "flash to pass" input to the BCM to enable all the lights. On the 03/04's the BCM switches the relays by "grounding" the coil but I believe the 01 and 02's may be different.

 

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I think there are laws in some states saying that the fogs cant be on with the high beams. There was a link someone posted a while back on another forum that verified this.


As far as resetting the fog light switch, I also find this VERY annoying as I want them on if my headlights are on.
 

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wxmn6So said:
before I tear the truck apart, I'd like to know if there is a way to make the fog switch stop from resetting itself everytime the truck is shut off? I am not sure if the fog light switch is computer or relay operated, but just want to know if it is do-able, and if so, how?
There's ALWAYS a relay in a head light circuit. However, in this case it's the computer that's out thinking you.
But there's no way to change that (short of getting aftermarket foglights, which can then be wired however you'd like).Edited by: JimWilson
 

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TEXMudder said:
...I think there are laws in some states saying that the fogs cant be on with the high beams.  There was a link someone posted a while back on another forum that verified this...
Thanks for pointing this out!
 

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Whats to stop you from adding a relay, tapping into 12V power, and wiring the existing lights to the existing switch through the new relay, and bypass the BCM. Then they will be wired just like an aftermarket set of fog lights. Everyone is happy that way.





Bill
 

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Redapple said:
Whats to stop you from adding a relay, tapping into 12V power, and wiring the existing lights to the existing switch through the new relay, and bypass the BCM. Then they will be wired just like an aftermarket set of fog lights. Everyone is happy that way.
Bill
Nothing to keep you from doing that, but the
switch. It's a gimpy sucker - if I could replace
it with a simple OEM looking on/off switch I would.
Problem is that the cargo light is also integrated
into the plastic carrier assembly too.

Do a search for some posts by Army & you'll
see how to do the "all lights on" mod. The
fogs will stay on with the highbeams or you
can make them function "normally" by adding
a switch. Here's some simple pictures;
Foglight Mod

hth,

T.
 

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Terry,

Thanks for posting the link to the light mod design ..
Excellent job documenting the install...

I had thought about using diodes like army did but I was worried (I worry too much
) about the BCM high beam relay driver having enough capacity to sink current for more than one relay. Apparently there is no problem since it's working.
I think I may change the harness I built to just boost power to the lights and use army's method for control.


Edited by: jbplock
 

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Thanx Terry,
You learned me something.

Bill
 

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Ditto Terry!! Excellent post with the pics and details!! Yet another wonderful Dmax project.
 
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