FITMENT / MEASURE BEFORE YOU MOUNT

Find your mounting dimensions.

Choose your model for mounting dimensions, bracket spacing and clearance.

Open the wiring wizard ↗Installation guide ↗

Choose your model

Choose the physical model. SHO, VHO and UHO describe the internals.

ZL2Dimensions coming soon ↗

Loading Z8i dimensioned CAD views…

WIRING KNOWLEDGE / FIND YOUR ANSWER

Electrical questions, answered.

Search 62 practical questions. Product pinouts, vehicle-specific connections and component ratings still require their actual instructions.

Search wiring questionsTopic

62 answers

Why is voltage at the light different from voltage at the battery?Voltage & current

Current flowing through resistance loses voltage along the positive wires, fuse, relay, connectors and negative return. Under load, the light sees the battery voltage minus all those losses. Measuring only at the battery misses that difference.

Blue Sea: length, drop & ampacity ↗

Exactly what type of wire should I buy?Wire & routing

Use flexible, stranded, full-copper automotive wire with insulation suited to the route. GXL and SXL with 125°C XLPE insulation are useful examples. Check the conductor specification, temperature rating and compatibility with your terminals; color and packaging gauge alone are not enough.

Southwire automotive wire ↗

Is copper-clad aluminum (CCA) acceptable?Wire & routing

This guide requires full copper. CCA has higher DC resistance, so the same current, gauge and length produce greater voltage drop. The copper table must not be used to approve CCA. A copper-colored surface or the word “stranded” does not establish a full-copper conductor.

Belden: CCA resistance ↗

What wire gauge comes with each light, and why might an extension need larger wire?Wire & routing

Z4i comes with 14 AWG wire connectors and R3 with 18 AWG. Their supplied lead lengths still need confirmation. The Z8i–Z20i factory pigtail is short: 12 inches of 8 AWG positive and 12 inches of return. A long extension adds much more resistance. Keep the supplied pigtail; choose customer extensions for their actual length and current. The planner calculates the segments separately.

Race engineering inputs & model limits ↗

Is the displayed fuse candidate the fuse I should install?Fuses & protection

It is a load-based starting point, not approval of that rating for the supplied cable or connector. Use Race’s actual harness specification and the fuse manufacturer’s temperature, pulse and time-current data. If those limits conflict, redesign the circuit instead of simply fitting a larger fuse.

Littelfuse automotive Fuseology ↗

Is a common 40 A relay enough for every light?Relays & controls

No. Compare the actual continuous DC contact rating at installed temperature with the planned load, and verify startup make/break capability. The socket and terminals also matter. Large loads can require a suitable contactor or rated solid-state output rather than a conventional relay.

Panasonic automotive relay guidance ↗

ELECTRICAL / ONE COMPLETE POWER PATH

See what reaches your light.

Battery voltage is not light voltage under load. Build the circuit, calculate each segment and print a two-page plan and installation checklist.

Use stranded, full-copper automotive wire.

Choose vehicle-rated insulation and terminals for the route. GXL/SXL with 125°C XLPE insulation are examples; tinned copper is fine.

CCA is not full copper. Copper-clad aluminum has greater resistance and voltage drop at the same gauge and length. “Stranded” alone does not guarantee copper. This calculator does not approve CCA.

Factory pigtail: 12″ positive + 12″ return, both 8 AWG.

The fixed leads stay in the calculation. Edit customer wire segments A–G below; the complete positive run and negative return must each remain at or below 15 ft, including the 1 ft factory lead.

Electrical versionBattery voltage under load · VModeled input power · W

Settled estimate with the relay closed. Coil input defaults to an example 0.15 A at 12 V. Unentered component resistances are excluded, so losses can be understated. Review assumptions and component values ↗

Same power, lower volts = more amps. Above 11 V at the light, the driver holds power approximately constant. Below that, MCU dimming changes the load. Each wire and contact uses some voltage under load, so the calculator solves voltage and current together rather than treating battery voltage as light voltage.

AT THE BATTERY13.80 V34.38 A main feed · coil supplied by ACC

AT THE LIGHT13.50 V34.38 A light input

MCU COMMAND100.0%Full power · 464.0 W modeled

MODELED PATH LOSS10.5 W0.30 V battery-to-light difference

Click a wire or its A–G label to edit. The toggle uses a fused ACC bus terminal. Do not splice into the main power feed.

Swipe or scroll sideways to inspect the diagram. Functional normally-open relay circuit. F2 protects the control feed at the ACC terminal bus. Enter measured loaded ACC voltage in component values to account for upstream vehicle losses. The toggle carries coil current, not the light’s main current. Crossings without a dot are not connected. Verify the actual device’s pinout, polarity and current ratings.

All wire values and factory leads Alternative table editor

Enter actual routed lengths. Factory pigtails are separate, fixed rows. Cable gauge alone does not establish ampacity; coordinate the fuse and every connector with the approved harness.

ID / connection	Length ft	Copper gauge	Current A	Drop V
A Battery + → main fuse F1Main power circuit			34.38	0.015
B Main fuse F1 → relay contact 30Main power circuit			34.38	0.046
C Relay contact 87 → positive pigtailMain power circuit			34.38	0.061
D Negative pigtail → approved returnMain power circuit			34.38	0.122
E ACC bus / control fuse F2 → toggle switchLow-current coil circuit			0.17	0.001
F Toggle switch → relay coil +Low-current coil circuit			0.17	0.001
G Relay coil − → approved returnLow-current coil circuit			0.17	0.001
Factory positive pigtail Fixed supplied lead · not a customer extension	1.00	8 AWG	34.38	0.030
Factory return pigtail Fixed supplied lead · not a customer extension	1.00	8 AWG	34.38	0.030

Compare battery voltages The light voltage and current are solved together

Battery V	Light V	Light current A	MCU command	Modeled path loss W
9.0	9.00	0.00	0.0%	0.0
10.0	10.00	0.00	0.0%	0.0
10.5	10.36	16.03	35.8%	2.3
11.0	10.72	31.27	72.3%	8.7
12.0	11.65	39.84	100.0%	14.1
12.6	12.26	37.83	100.0%	12.7
13.8	13.50	34.38	100.0%	10.5
14.4	14.11	32.89	100.0%	9.6

Battery values are scenarios, not guaranteed charging-system voltages. A lower voltage can increase current in constant-power operation, then reduce it once MCU dimming is active.

11 V → 100% · 10.5 V → 50% · 10 V → 0%

The MCU curve is evaluated at the light, after wiring losses. Input power is modeled as following that command. Optical output and standby electronics are not established by this curve.

Fuses, relay capacity and rapid dips 9.0 V protection basis

11 V CURRENT REFERENCE42.2 ARated power ÷ 11 V

RAPID-DIP LOAD BASIS · 9 V51.6 ARated power ÷ 9 V before a delayed MCU response

RELAY CONTINUOUS PLANNING TARGET≥ 65 A25% margin on the 9 V basis, before temperature and DC LED inrush qualification

Protection uses 464.0 W, at least the selected model’s maximum reference. The MCU can be slow to react to rapid voltage drops. The steady-state dimming table cannot establish that transient waveform. The load-based main-fuse candidate is 70 A, using a 75% continuous-load allowance; it is not approval for the supplied leads, connector, holder or relay. Follow Race’s harness fuse specification and the actual fuse’s time-current, pulse, temperature and interrupt ratings. Protect the small control branch separately at the ACC bus terminal.

Actual main fuse F1 · AActual control fuse F2 · A

Component values, assumptions and sources

ACC bus voltage with ignition ON · VCopper conductor temperature · °CRelay coil current at 12 V · AMain fuse path resistance · mΩMain relay contact resistance · mΩOther main-path connections · mΩControl fuse, toggle and terminals · mΩ

The coil is modeled as resistance derived from its entered 12 V current, not a specific relay’s measured curve. Coil temperature and pickup/hold thresholds are not qualified; contacts are assumed closed. Blank ACC voltage assumes battery voltage. Enter a measured loaded ACC bus voltage to account for upstream vehicle losses. A solid-state controller requires its own topology. For R3, the Zenith low-voltage curve is not assumed.

The model sums each segment’s resistance, uses a main battery feed carrying only light current and an independent fused ACC feed carrying coil current, and solves the light voltage and current together. Constant power applies at ≥11 V. Between 10 and 11 V, modeled input power follows the supplied linear MCU command; at ≤10 V the modeled LED load is zero. Standby current, exact optical output, MCU delay/hysteresis, battery dynamics and thermal ampacity are not established here. The calculator flags multiple stable equilibria.

Power uses the larger of the reference watts and the reference 12 V current × 12 to avoid optimistic catalog rounding. Coated stranded-copper resistance comes from Southwire table 2-6, temperature-adjusted using the NIST coefficient. All component resistance inputs remain estimates until verified from the actual hardware or loaded measurements.

Have Race review the plan and actual component part numbers ↗

Z8i UHO · Wiring plan

464 W modeled · battery 13.8 V · ACC 13.8 V (tracks battery) · copper 105°C · one light / one circuit

Planning worksheet, not a factory pinout or approved harness. Toggle feed: fused ACC terminal bus, no main-feed splice. Relay contacts assumed closed. Some component losses are unmeasured and excluded. Verify component ratings, polarity, fuse coordination and loaded voltage before use.

Light: 13.50 VLight current: 34.38 ACommand: 100.0%Loss: 10.5 W

Wire segments · lengths exclude the fixed factory pigtails
ID / connection	ft	AWG	A	Drop V
A · Battery + → main fuse F1	0.5	8	34.38	0.015
B · Main fuse F1 → relay contact 30	1.5	8	34.38	0.046
C · Relay contact 87 → positive pigtail	2	8	34.38	0.061
D · Negative pigtail → approved return	4	8	34.38	0.122
E · ACC bus / control fuse F2 → toggle switch	2	14	0.17	0.001
F · Toggle switch → relay coil +	2	14	0.17	0.001
G · Relay coil − → approved return	1	14	0.17	0.001
Factory + / − · fixed, each	1 / 1	8 / 8	34.38	0.030 each

Steady state at battery voltages
Battery V	Light V	Light A	Command %
9.0	9.00	0.00	0.0
10.0	10.00	0.00	0.0
10.5	10.36	16.03	35.8
11.0	10.72	31.27	72.3
12.0	11.65	39.84	100.0
12.6	12.26	37.83	100.0
13.8	13.50	34.38	100.0
14.4	14.11	32.89	100.0

Hardware & rapid-dip basis

F1 main fuse: Not confirmed (70 A load-based candidate only).

F2 control fuse: Not confirmed. Coil input: 0.15 A at 12 V (entered assumption).

464.0 W protection basis. 11 V current: 42.2 A. Separate 9 V rapid-dip basis: 51.6 A. Relay/contact continuous planning target: ≥ 65 A before derating/inrush checks.

MCU command: 100% at ≥11 V; linear to 0% at 10 V. This is settled behavior, not a dip waveform. Standby current, optical output and dynamic recovery are not modeled.

Component path inputs, mΩ: F1 0, relay 0, other main connections 0, control path 0.

Install it once. Install it well.

Z8i UHO · Keep this checklist with your wiring plan · 2 / 2

A short checklist for a durable off-road installation. Follow the vehicle, light, connector and protection-device instructions for your exact hardware.

Keep runs short. Use the shortest practical protected route for positive and return wiring. Leave a small service loop for aiming and connector access; avoid coils of excess cable.
Choose full-copper stranded automotive wire. Select insulation, gauge and terminals for current, length, temperature, fluids and exposure. Supplied wire size does not set the size of a long extension.
Crimp with the correct tooling. Match the terminal to the conductor and insulation size. Use the specified die and strip length, inspect the finished crimp and gently check retention. Support the wire so vibration does not load the contact.
Seal exposed joints. Use sealed automotive connectors and correctly sized adhesive-lined heat shrink where the joint design permits it. Apply controlled heat per its instructions; keep connector seals and mating faces clear.
Protect and secure the route. Use temperature- and abrasion-rated sleeve or loom, grommets at metal pass-throughs, and suitable cushioned clips. Allow for steering, suspension and engine movement without tension or rubbing.
Protect both circuits at their sources. Put F1 near the battery feed and F2 at the ACC bus terminal. Confirm fuse, holder, relay, connector and cable ratings together. Use the OEM-approved return path and terminal torque.

AVOID

Heat and moving parts. Keep clear of exhausts, manifolds, turbos, belts, fans, driveshafts and moving suspension or steering parts. Check the full movement range. Loom is not permission to run against a hot surface.
Sharp edges and pinch points. Do not trap wiring under brackets, seats or body panels, or stretch it across joints. Do not let cable ties crush insulation. Protect against stones, tire contact and pressure-wash exposure.
CCA and unsuitable cable. Copper-clad aluminum has greater voltage drop than full copper of the same gauge. Avoid household solid-core wire and insulation unsuitable for the installed environment.
Twist-and-tape or unsupported solder joints. Solder only where the terminal or OEM procedure calls for it. Excess solder can wick into strands and create a stiff flex point. Never use solder to rescue a poor crimp; support and seal an approved soldered joint.
Unprotected taps and oversized fuses. Do not splice the toggle feed into the main power cable. Use the fused ACC terminal. Do not fit a larger fuse to cure repeated blowing or assume app dimming replaces circuit protection.
Unverified grounds and terminal stacks. Do not bypass a battery-current sensor or use an arbitrary painted fastener as a return. Keep terminal connections accessible, protected and within the hardware maker’s stacking instructions.

BEFORE THE FIRST DRIVE

□ Isolate power using the vehicle’s procedure before wiring. Fit fuses after inspection. □ Confirm polarity, terminal markings, secure fasteners and connector locks.

□ Test under load: record battery voltage, voltage at the light and current. Compare with page 1. □ Check for abnormal heat, flicker, rubbing or a loose connection; stop and investigate if found.

□ Reinspect after the first rough-terrain outing and periodically thereafter. Keep the plan and component part numbers for service.

Need a second look? Send your plan, component part numbers and routing photos to info@racelights.com. More answers: racelights.com/fitment → Electrical → Search wiring FAQ.

Further guidance: TE Connectivity · automotive splice sealing; Ford · vehicle-specific harness routing. Example references do not replace your vehicle’s instructions.