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GT Headlights

Inspecting the Opel GT Headlight Wires, is a requirement for safe operation!

Opel GT Headlight Rewiring Tips: ALL OPEL GT's NEED their headlights rewired!GTHeadlightArrow03

The unique horizontal twisting and turning of GT headlights, after 30 years' time, cracks the old dried-out rubber insulation on the high current headlight wires, causing electrical shorts in the un-fused circuit, and has even caused fires in the engine compartment. Because of these severe consequences, you need to perform this repair ASAP as a preventative measure !!

To visually inspect, turn ignition key off and open the headlights and unscrew 3 screws holding down metal headlight lid. The area of most critical wear, is where the wire loom rotates behind the bulb; you can peel back some insulation here to view cracked rubber and bare wires. Additional symptoms may include: Failure of headlights, Failure of main (7-wire) headlight relay, and/or the amp gauge "pegging" when lights are switched on. (Refer to article for other GT headlight/micro-switch diagnoses).

**NOTE: This procedure is for "driver" Opel GT's, as it leaves in place, some of the original circuit. If GT will be restored factory-original (or judged in a car show), either the original harness will have to be opened up and then re-taped, or completely replaced with an original-style replacement headlight wiring harness. Read all the notes, and have all parts ready, before starting.

Special Parts Required:

  • 10 feet of 12-gauge wire: White, Yellow and Brown**
  • 25 feet of Black Electrical Tape or Specialty Wire Wrap
  • 2 Headlight Connectors, 3-Prong Type; Solder and Flux;
  • 15 Black Wire Ties, Small Diameter; 2 Eyelet connectors
  • Flex Tubing, 15mm Outer Diameter, 2 pieces each 12" long
  • (Optional) Electrical Wire Sleeve (max ½" O.D.);
  • (Suggested) 2 Electrical Connectors, 3-Wire Detachable

Special Tools Required:

Wire Cutter, Solder Iron, Coat Hanger, Exact-o Knife


Disconnect battery cables. Open headlights and remove metal lids  (See: "L" or "R" stamp on middle right lip of each lid; they are side-specific). Cut the wires to the 3-prong connector to the back of the headlight bulb.original_splice

Starting with the passenger "R" side: Inside front wheel-well, remove the 4 phillips-head screws holding the access plate (you have to scrape some undercoating off the heads of these 4 screws, to be able to turn them).

Prepare replacement wire loom. Cut 10' of each of the three wires into 2 lengths, 7 ¼ feet (87") for the passenger side, and 2 ¾ feet (33") for the driver's side. (Unless ½" O.D. electrical wire sleeve is used), tape a loom of three-color strands into a tight "triangle" at least 12" from one end, using overlapping, evenly spaced layers for clean look and protection. This loom must fit through a narrow 15mm hole, So keep wires straight and tight in the new loom.

pass_sideAttach the end of this new 3-wire loom to the ends of the old wires by wrapping and taping them together, then from inside the wheel-well pull on the old wires, back from the bulb area back into the wheel-well. Push the end of a coat hanger from the engine area through the wiring grommet (in the front corner area) into the wheel-well area, then attach the end of the coat hanger to the 3-wire loom and securely tape together.

Carefully pull these wires back through the grommet into the under-hood area (It's a tight 15mm fit, so use some WD-40 or Vaseline to lube and protect the grommet and the tape on the new wire loom). Detach the ends of the new wires from the old wires, then cut into the old loom a couple of inches and cut off the old wires back in the old loom. Back at the headlight buckets, ensure that un-taped wire ends run through section of 15mm flex tubing in hole in headlight mechanism (to avoid chafing during rotation).GTBULB2

If a 3-wire detachable connector is used here (preferred, as it allows future removal without cutting wires), install it and solder or connect wires to the 3-prong type headlight bulb connector. Make sure wire colors are in correct location at headlamp bulb (see Diagram, at Right).

Repeat wire replacement procedure on driver's side of car.flex_tubing

Then, for a clean look, use the black wire ties to neatly secure the new passenger-side loom to the old harness, where it goes in front of the radiator and back towards the master cylinder. You can also wire-tie the driver-side harness where it crosses under the master cylinder.

Separate brown (ground) wires from ends of the new wire looms near the Master Cylinder, then splice the yellow wire and the white wire to the existing wire harness. You have 2 options for location: The easiest to access, is on the main harness in the driver's side of the engine compartment, about 10" towards the rear from the radiator support beam. Unfurl the metal clips, then pull the main harness out from under the inner lip of the fender. The original splice location is near the master cylinder (where original wires connect 2-into-1 in the loom) but unless you insist on originality, it's a tight area for the splicing and soldering work.

new_wiresOpen up the loom, by cutting sleeve lengthwise about 8" with an exact-o blade, then locate, tug out and cut the white wire and yellow wire (forward of area to be spliced). Prepare to splice the ends of the replacement white wires to a small section of the original white wire (use blade to strip a 1" area of insulation, or two separate ½" areas "staggered" for a cleaner look). Place some cardboard below the area for protection, then carefully solder (using lots of flux) these wires together. Let cool, then use this same approach but about 1" back , to solder the replacement yellow wires to the original yellow wire. Let cool, then tape up the loom, and hide the splice area by securing it with the clips under the inner lip of the fender.

Connect brown wires to chassis ground, by adding a round "eyelet" to wire ends and attaching with self-tapping screw to existing hole in engine area sheet metal (& sand off rust/paint there) on inner fender-well behind master cylinder (see photo).

Re-inspect all connections, to make sure they are secure and well insulated. Reinstall metal headlight lids.
Reinstall 4-screw metal access plates in fender-wells. Reconnect battery cables. Test headlights for proper function.

Additional pages of the above article, including simplified instructions of:

— How to diagnose GT headlight circuits for relay and micro-switch failure
— How to install a headlight relay bypass switch, and
— Summaries of past articles concerning the Opel GT headlights; Including those in back issues of the OMC Blitz (and other sources, like prior Opel clubs), is available by ordering this OMC August 2004 Blitz newsletter back issue, for $2.00 by mail (includes US postage), from the OMC Treasurer, 3824 Franklin Ave, La Crescenta CA 91214-1607.

We encourage every Opel enthusiast to join the Opel Motorsport Club, to acquire your own collection of these tech tips!

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