Headlights DIM when fogs on!!!!!!!

jmildoc

jmildoc

New member
So Millerad and I installed some driving lights on my T4R on friday after work, and after much hassle with the wiring we used the stock fog light wires. Only problem is when I turn the lights on, the headlights dim to about half the brightness. They have a relay and are run on the stock Hella 500 harness.

Any help would be appreciated.

Here are the lights we installed.

Original plan was to use them for reverse lights under the truck but they ended up being too big. Navigator NV-1204" x 6" Clear Fog Light with Stone Guard and Cover : Amazon.com : Automotive
 
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It can't hurt to check. use a jumper and run a ground to the battery and see if the dimming goes away.
 
the only way i have got the dimming to go away is run straight power from the battery to the lights.

Is this safe to do? then i can turn the lights on anytime I want right?
 
jmildoc said:
the only way i have got the dimming to go away is run straight power from the battery to the lights.

Is this safe to do? then i can turn the lights on anytime I want right?
Click to expand...

That's what I did with my 4" PIAA's. It's safe to do. It's not going to drain the battery unless the lights are on when the car is off. I just ran my power switch straight to the battery and it hasn't drained it at all.
 
jmildoc said:
the only way i have got the dimming to go away is run straight power from the battery to the lights.

Is this safe to do? then i can turn the lights on anytime I want right?
Click to expand...

That's what I did, and was thinking about doing with yours. But we wouldn't have been able to use the pre-existing harness and switch wiring. That is how I have mine wired. We can reuse the relay you bought, and just wire the directly in with the in-line fuse.
 
It's hard to visualize what you are doing exactly. The power to the relay contacts should be straight to the battery with an in-line fuse or drawn from an auxiliary bus. Even with constant power to the contacts, the supply to the switch/relay coil circuit can determine when the lights can come on; anytime, key on, highs on, lows on, or either highs or lows on.

That said, here is a wild guess. The stock fog light coil circuit is powered from the headlight circuit so that the lights only come on when the low beams are on. I figure somehow you tapped in so that the coil side supply is being used to power the fog lights (which should be from the contact side) overloading the headlight circuit.
 
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you need to replace the wiring that you used for the new fog lights with bigger wires. then use a relay to power the fogs from the battery but use the stock wires to activate the relay from your stock switch. these means you'll also use bigger wires for grounding the new fog lights
 
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I have the same problem but with my stock lights.... The only thing is I have my two 10 watt LED driving/strobe lights tapped to the fogs. Positive only though. The steady burn comes on when the parking lights are on, as seen in my signature pic. The strobe function activates when I turn on the fogs (that still work and turn on). But the headlights also dim down a bit.....
 
Well I am going to pull out the factory harness and rewire it all to see if I can get it to work how I want it to work, and that is, anytime I put them on. And then the next step is, next month I am getting two sets of Dually knock off Hanma LED spot, and flood lights. I will have light dang it!
 
Since you have a 1998, you do not have DRL's and the headlights are switched grounds. This means one side of the stock fog light relay coil is connected to the switched ground lead of the low beams,. You need to switch that relay coil ground to a full-time ground. Odds are it goes lowbeam switched ground to stalk switch to relay coil and the 12V+ is on the other side of the relay coil. So the surgery has to occur at the stalk to feed the fog switch from a full-time ground. I don't have access to non-drl wire diagram (MY '99 and earlier) so I am just guessing. The switch could also be on the 12v+ side of the relay coil, but that would require an extra wire to the stalk.

Worst case, the connection is internal to the stalk and then I don't know how you could do it and keep the stalk switch.
 
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So why was there a wire coming from my headlight switch behind my dash.

When I grounded that wire it made my hi's and low's stay on. Pretty neat actually. Think this would be okay to run a switch so I can do this when needed?
 
This is what I went by and I still can't get them to work.
ba9y4yge.jpg
 
jmildoc said:
This is what I went by and I still can't get them to work.
ba9y4yge.jpg
Click to expand...

There is nothing wrong with the diagram. Are you using the stock fog wiring and switch? Exactly where are you connecting the 85 and 86 terminals? One of these has to be a ground and the other has to have 12V+ for the lights to come on. It doesn't matter which has which. (I am guessing you do not hear the relay click when you work the switch. If you do, the problem is on the other two terminals, where you need ground>>light>>relay #87 and battery>>fuse>>relay #30. If there is 12V+ at the lights, the issue is the grounds.)
 
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I do hear the relay clicking when I toggle the switch.
Gonna run new better grounds to both lights and see if that helps.
 
jmildoc said:
I do hear the relay clicking when I toggle the switch.
Gonna run new better grounds to both lights and see if that helps.
Click to expand...

This is where you need to get a test light or VOM and troubleshoot, not just mess around with the wiring. I've been doing this a long time.
 
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