Depot headlight wiring for hight beems
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Article by Fred Jensen

For some reason, only known to GM, your C5 (and maybe other generations) turn off your Low Beams when the High Beams are turned on. With stock Pop ups I did not see it as a problem. But, I just installed the DEPO Projector Headlights, mostly as I was tried on the Pop ups and fixing them. As they look installed:

The Depot headlights are very good, but the high beams must have been designed thinking the low beams also stay on as these high beams hardly “touch the road” near your car when they are on. However, with lows on and “flashing” the highs lighting is excellent.
So, I decided to do a mod to have the lows be on when the highs were selected. I also wanted to do it so even if I wanted to go back the stock Pop ups, I would get all the light my car could provide (all 4 on at once). The below mod works with stock and non-stock headlights for under $15 and is a quick and easy to do.

The basic design is to use a relay SPST (single pole / single through about $6 at Radio Shack or elsewhere) to switch on / provide power to the low beams when the highs are turned on. The connections that need to be made from passenger side wire harness are:
High beam (black wire) to relay coil
Ground (green wire) to relay coil
Low beam (Ivory wire) to switched side of coil
A wire from the battery terminal under the fuse box cover by the battery to other switched side of coil. (This is where the power to light the low beams comes from, goes through the relay when it is energized / engaged and into the Ivory low beam harness wire and flows to both sides of the car)
(Polarity is not an issue, but obviously which of the 4 connections each wire is connected to is)
As per the photo everything can be done in the engine compartment on the passenger side.
photo of C5 corvette

Implementation notes / suggestions:
Harness wires are small (about 20 GA) so get / use other wires and connectors that are sized accordingly.
Spade connectors are best to connect wires to the relay. I used heat shrink tubing over them and cut about ¼ long to cover the exposed relay connector. Just use a match to heat the wire end and the part that will be by the relay will stay open as a “sleeve”.

Best to connect into the harness wires would be Quick Slide (T-Taps) Connectors as there is not much harness wire available for cut & slice connections. But, other options can work. It is not necessary to run an additional wire to the driver side low beam as the wire in the passenger side wire harness also connects to that side somewhere in the harnesses. I put fuses on the new wire I ran from the battery / fuse box connection and on the High Beam to Relay Coil wire for extra safety. The relay has a “tab” with a hole in it to attach to something. I drilled a small hole and used a pop rivet. That location is a thin plastic that goes through to and is also part of the wheel well. When you’ve done this, when you switch on the High Beams the voltage actuates the relay connecting the power from your battery wire to the Low Beams. Since ½ that power goes the 1 foot to the passenger side light and the other ½ goes a few feet through existing wiring to the driver Side Low Beam none of the wires gets more power than they would normally and wire size is not a power issue. Further, when you “flash” your lights instead of just Highs, you also get the lows (I think a nice upgrade to get slow people to move over.  




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