Fog Lights with High Beams Project
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Part 1
Here's the modifications neccessary to keep the Fog Lights ON while using High Beams on a '97 to '99 Grand Prix!
Pull relay #17 out of it's socket and bend contact #2 (Labeled on the bottom of relay) out and up. This allows the new ground wire to be attached to relay #17 and disconnects the relay from the light green wire at the same time. (No factory wire cutting required! Easily reversible!) Slide the spade lug of the new jumper wire over the relay contact that is sticking out and place relay #17 back in it's socket. Pull relay #11 out of it's socket and stick the other end of the jumper wire into the ground contact of relay #11. Place relay #11 back into it's socket. Both relays will probably sit a bit crooked but shouldn't hurt anything.
NOTE: Make sure that the word "OMRON" (or other manufacturer's name) reads properly
after doing this modification. If relay #17 is plugged in upside down, it might not work right.

Schematic from page 8A-11-0 of '98 Service
Manual
Please note that the various colors shown are for reference only. They won't look this way on your car. Also, the Yellow, Red, Purple, and Light Green wires in the above schematic are internally connected and not visible without complete dissassembly of the UnderHood Junction Block.
 
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Part 2
Here's the modification needed to make the Fog Light switch work properly after making the modification to the relay in Part 1.
This requires removal of the Fog Light switch from the dash. (I checked for an easier method of getting to these wires but they run along the top of the dash for a while and connect to 2 other circuits along the way to the UnderHood Junction Block so changes are most easily made at the switch location.) Here's my preferred method:

Inside view of Fog Light switch

Below is an alternative method that involves the wires that run to the Fog Light switch. I don't like this method as much for 3 reasons:
  • It requires cutting factory wiring
  • It requires working and soldering near the dashboard
  • It's not easily reversible

  • Alternate Fog Light modification

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