Complete Section 2.1 — Grounding Kit first. A headlight relay harness routes full battery voltage to the bulbs — but that voltage still needs a clean ground return path to work properly. Do the grounds first or you are only solving half the problem.
Why OBS Headlights Are Genuinely Dangerous — and Why It's Not the Bulbs
The OBS headlight circuit has a fundamental design flaw that was marginal from the factory and has gotten progressively worse over 30 years. In the stock system, the full headlight current — both bulbs, both high and low beam filaments — passes through the headlight switch on the dashboard. That switch was not designed for sustained high-current use and its contacts corrode, arc and degrade over time.
The result is that by the time an OBS truck is 25-30 years old, the headlight switch is introducing significant resistance into the circuit. Your 60-watt headlight bulbs are receiving perhaps 45-50 watts of actual power. You have paid for a torch and received a candle. On UAE roads at night — where the combination of unlit camels, sand on the carriageway and vehicles with no lights whatsoever is a genuine hazard — this is not a minor inconvenience.
A relay harness solves this completely. It uses the existing headlight switch circuit only to trigger a relay — a tiny electrical signal, no current load on the switch — while routing the actual headlight power directly from the battery via a relay and a fused heavy-gauge cable. The bulbs receive full battery voltage. The switch lasts indefinitely. Night visibility transforms.
Stock vs Relay Harness
✗ Stock Circuit — The Problem
Full headlight current passes through the dashboard switch, through 30-year-old wiring, through corroded connectors — arriving at the bulbs with significantly reduced voltage.
→ Fuse box
→ Dashboard headlight switch ← HIGH RESISTANCE HERE
→ Corroded connectors ← RESISTANCE HERE TOO
→ Headlight bulbs
→ Ground (also corroded)
✓ Relay Harness — The Fix
Switch circuit carries only a tiny trigger signal. Full battery power routes directly to bulbs via new heavy-gauge wiring and a relay. Bulbs receive full voltage.
→ New fused heavy cable
→ Relay (triggered by switch signal)
→ New direct wiring
→ Headlight bulbs ← FULL VOLTAGE
→ New direct ground
What You Actually Gain
What You Need
The Harness — One Part, Complete Solution
- Painless Performance Headlight Relay Harness — OBS specificPainless Performance 30102 or equivalent
Optional — Upgrade Bulbs at the Same Time
- H4 LED Bulb Set — plug-and-playPhilips RacingVision or equivalent — verify H4 fitment
- H4 Halogen Upgrade — if preferring halogenOsram Night Breaker or Philips X-treme Vision
On LED bulbs: LED headlight bulbs work well with a relay harness — they finally receive the stable full voltage they need. However, some LED bulbs cause interference with the OBS radio or gauges. If this happens, the bulb has no EMI suppression built in — try a different brand before blaming the harness.
What It Will Cost (AED)
| Item | Source | Est. Price (AED) |
|---|---|---|
| Headlight Relay Harness | Order via Aramex from Summit Racing / Amazon US | 180 – 300 |
| LED Bulbs H4 (optional upgrade) | Sharjah / Dubai auto parts | 80 – 200 |
| Labour | Independent mechanic — simple job | 80 – 150 |
| Total — Harness Only | 260 – 450 |
The Painless Performance harness is not commonly stocked in UAE. Order via Aramex from Summit Racing — allow 7–10 days. Alternatively, a competent auto electrician in Sharjah can build an equivalent relay harness from components for similar cost.
The Process
- Disconnect battery negative before starting.
- The relay harness plugs inline between the existing headlight connectors and the headlight bulbs — no cutting of factory wiring required on most kits.
- Route the new power feed wire from the battery positive terminal through the engine bay to the relay location — typically near the headlights behind the grille.
- Connect the relay trigger wires to the existing headlight connectors — these carry only the switch signal, no high current.
- Connect the new output wires directly to the headlight bulb connectors.
- Mount relays securely in the engine bay — away from heat sources and moving parts.
- Reconnect battery. Test all functions — low beam, high beam, both sides.
- Adjust headlight aim if needed — brighter output can reveal incorrect aim that was previously not noticeable.
Hand This Over
"Fit the headlight relay harness provided. The harness routes direct battery power to the headlights through a relay — the existing headlight switch wiring is used only as a trigger signal, not to carry the main current. Do not cut any factory wiring — the harness plugs inline. The new battery power feed wire must be fused at the battery end — the fuse is supplied with the harness. After fitting, test both low and high beam on both sides, then check headlight aim."
This Guide Covers
All OBS trucks use the H4 headlight bulb format and share the same fundamental headlight circuit design. The relay harness approach applies across the entire platform.
Continue the Wiring Section
- Next — 2.3 Rear Tailgate Loom (K5 Blazer two-door) — if your reverse lights, number plate lights or rear washer are intermittent, the tailgate hinge loom has failed. Specific to the two-door K5.