Posted: Fri Oct 14, 2011 4:50 pm Post subject: Foglights on with headlights but not with DRLs ('05 Impala)
I just wanted to make a note of how I was able to accomplish my goal for anyone else who may come along trying to do the same thing.
In order to get the fog lights to kick on when the headlights were turned on but not while the DRLs were on, I took BBEngineer's advice of tapping into the control wire for the Headlamp Relay (Blk/Wht wire coming out of B3 pin of the pink BCM plug) and used this to trigger the fog light relay.
To eliminate the fog lights while the high beams were on, what I did here was to add a second relay to break the circuit between trigger wire for the fog light relay. It was really a simple process once I got some sleep and sat down to think about it.
The wiring schematic goes something like this:
Fog Light Relay:
85 To High Beam Control Relay pin 87A
86 To Headlamp Relay control lead from BCM (Blk/Wht wire, pin B3, pink connector)
87 12V power for fog lights (run off the battery--don't forget to use a fuse!)
30 Fog light positive lead
High Beam Control Relay:
85 12V power lead (Just needs to have enough power to trigger the relay)
86 High beam ground
87A To Fog Light Relay pin 85
30 12V power lead (Just needs to have enough power to trigger the Fog Light Relay)
If desired to have a manual off switch you can have your trigger lead from the headlamp control lead run through a toggle switch before going to the fog light relay.
Thanks again BBE for the headlamp relay tip - I had first thought of this but wasn't sure if the DRLs went through it or not and I didn't have a schematic for 2005 headlight/DRL system. The help was much appreciated.
Okay, so I got myself some fog lights and I want to wire them to automatically come on anytime the headlights are on. My first thought was to use the low beams as a trigger for my fog light relay. But then I had an "oh wait" moment since my low-beams are also my DRLs. Second thought was to use the parking lamps -- but here again, I need the fog lights to turn off when I move the headlight switch to parking lights only so that is out as well.
My haynes manual only has the pre-2005 wiring diagram so I can't verify if I were to tap into the signal to the low-beam relay would that also be triggered by the DRLs or not.
Does anyone have a 2005 wiring diagram for the headlight system / DRL System I can use to reference so I can accomplish my goal? I've tried searching but haven't come up with anything...may be due to running on 3 hours of sleep, I don't know but any help would be appreciated.
_________________ 2005 Chevy Impala 9C1
Last edited by blackkodiak18 on Sat Oct 15, 2011 1:37 pm; edited 1 time in total
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