Universal dual electric fan wiring harness kit, 40 amp relays, high and low speed
Universal dual electric fan wiring harness kit, 40 amp relays, high and low speed
Two Independent 40 Amp Circuits with 630-Series Fan Connectors
Item #: FNWK-004
Product Overview
Modern dual fan setups draw serious current. Many OE and aftermarket fans pull upwards of 30 amps each on a continuous basis, and factory fan circuits, relays and fusible links were never sized for it. Running high-output fans through the factory circuit costs you voltage at the motor, which costs you airflow — and eventually melts a relay terminal or a fuse centre.
This kit pairs the DRPH-001HD dual relay power harness with two RCS-011 Metri-Pack 630 connector sets, so each fan gets its own fused, relayed 40-amp circuit fed straight from the battery, terminated in a sealed connector rated to 46 amps.
Kit Contents
| Qty | Component | Description |
|---|---|---|
| 1 | DRPH-001HD | Dual 630 Relay Power Harness HD — two independently fused and relayed 40-amp circuits on 10 AWG copper. |
| 2 | RCS-011 | Connector Set, Metri-Pack 630S — one male body, one female body, orange cable seals, and three male plus three female terminals (one spare of each) with terminal lock. One set per fan. |
| 1 | RCS-022 | Connector Set, 4-Way Metri-Pack 150 Sealed — male and female bodies, terminal locks, cable seals and five male plus five female terminals. For an optional disconnect in the four relay coil wires. |
The connector sets are supplied loose with unterminated terminals so they can be matched to your specific fan leads and control wiring.
How the Two Circuits Work
The two circuits are completely independent. Each has its own fuse, its own relay and its own pair of coil wires, which means you decide how the fans are staged:
- One fan at a time — trigger a single circuit for light load and city driving.
- Both fans together — trigger both circuits when heat load climbs.
- Two separate control sources — run one fan off a thermostatic switch and the other off the PCM, or off a dash switch for manual override.
Each circuit switches its fan fully on or fully off at full battery voltage. If you want a genuine low and high speed from a pair of fans on a single control, look at our FNWH-007 series/parallel harness, which wires the two motors in series for low speed and parallel for high.
Optional Coil Wire Disconnect
The four relay coil wires run 8 ft, which is long enough to reach a cabin switch or a controller mounted well away from the battery. That length is useful during installation and awkward afterwards, if you ever need to pull the harness out.
The RCS-022 4-way Metri-Pack 150 set lets you put a sealed disconnect in the middle of those four wires, so the harness can be unplugged from your control side without cutting anything. Both coil pairs pass through one connector, keyed so it can only go back together one way.
It is entirely optional. If you would rather run the coil wires straight through to your switch or PCM, leave the connector in the bag.
Wire Identification
| Wire | Gauge | Function |
|---|---|---|
| Red | 10 AWG | Circuit 1 switched positive output to fan |
| Blue | 10 AWG | Circuit 2 switched positive output to fan |
| Black ×2 | 10 AWG | Ground — two 48" wires to the fan connectors, joined at a single chassis ring terminal |
| Red | 20 AWG | Circuit 1 relay coil positive |
| Black / pink stripe | 20 AWG | Circuit 1 relay coil negative |
| Blue | 20 AWG | Circuit 2 relay coil positive |
| Black / light blue stripe | 20 AWG | Circuit 2 relay coil negative |
How each fan connects
Each fan is fed through one of the two RCS-011 connectors, carrying both sides of the circuit:
- Positive — the 10 AWG red or blue output from its relay, on a 12 ft run back to the battery.
- Negative — one of the two 10 AWG black ground wires.
The two black grounds share a single ring terminal, which bolts to the chassis close to the fans — the frame on a body-on-frame vehicle, or a solid point on the unibody. That is why the grounds are 48" while the power legs are 12 ft: the return path stays short and local rather than running all the way back to the battery.
A fan drawing 30 amps returns 30 amps through that ring terminal. Paint, seam sealer, rust or a factory body-to-frame strap that has aged out will cost you voltage at the motor exactly the way undersized positive wiring does, and it is the harder fault to find afterwards. Scrape to bare metal, use a star washer, and check the body-to-engine and body-to-frame bonds while you are there.
If those bonds are marginal, our BGC series body ground cables are listed in the add-ons below.
Harness Layout & Lengths
| Battery to fuse holders | 36" — 10 AWG red and blue, terminated in 3/8" ring terminals |
| Fuse holders to relays | 12" — 10 AWG red and blue |
| Relay output to fan | 144" (12 ft) — 10 AWG red and blue, pre-stripped and may be trimmed to length |
| Ground | 48" — two 10 AWG black wires to the fan connectors, joined at a single chassis ring terminal |
| Coil wires | 96" (8 ft) — 20 AWG, long enough to reach a cabin switch or engine bay controller |
Engineering Specifications
- Two 40 Amp Circuits: Independently fused and independently relayed, one per fan.
- 10 Gauge Throughout: Heavy copper on both circuits and the ground for minimal voltage drop under sustained load.
- Sealed 630-Series Relays: Shrouded, sealed 40-amp relays rated for exposed under-hood environments.
- Sealed 630-Series Fuse Holders: Weather-sealed inline holders on each circuit, shipped fused at 30 amps.
- 46 Amp Fan Connectors: Metri-Pack 630S sealed sets, 10–12 AWG, rated 0–46 amps with a voltage drop under 3.0mV per amp, temperature rated -40°C to 125°C.
- Sealed 4-Way Coil Disconnect: Metri-Pack 150 sealed set for the four coil wires, rated 0–14 amps against a coil load of roughly 100mA per relay.
- Fully Isolated Relay Coils: Both coil leads brought out on each circuit, so either side can be switched — positive-switched, ground-switched, or one circuit each way.
- PCM / ECM Safe: Internal suppression resistors protect solid-state drivers, so the relays can be triggered directly from engine management outputs.
- High-Temperature Nylon Loom: GM specification GMP.PA6.003, rated -40°F to 300°F, covering the entire harness.
- Fully Labeled: Every connection, fuse and relay is marked, so circuits stay traceable years after installation.
Before You Install
The RCS-011 connector sets are supplied with loose terminals so they can be matched to your fan leads. Proper B-type crimping tools are recommended. Each set includes one spare male and one spare female terminal.
Each circuit is rated to 40 amps and ships fused at 30 amps. The installation kit supplies spare ATC pairs in 20-, 30- and 40-amp ratings along with matching fuse holder labels, so you can fuse to the measured draw of your fans rather than to the harness ceiling.
Once you have settled on a rating, cut the matching label from the strip and apply it to each fuse holder cap. The caps are opaque, so without a label there is no way to tell what is fitted without opening them — and if you ever change the fuse rating, change the label with it.
Frequently Asked Questions
Q: Does this give me a low and a high fan speed?
A: Not per fan. Each circuit runs its fan at full voltage. You get staging — one fan or both — rather than two speeds from one fan. For true series/parallel two-speed operation, see FNWH-007.
Q: Can I trigger this from my PCM or ECM?
A: Yes. The 630-series relays have internal suppression resistors, so no external resistor or diode across the coil is required. Hold the coil positive at +12V and let the PCM pull the coil negative to ground — the coils are fully isolated, so a ground-switched output drives them directly without risk to the solid-state drivers.
Q: Are the fan connectors pre-terminated?
A: No. Each RCS-011 set ships with loose terminals and orange cable seals sized for 10–12 AWG, so you can terminate them to your own fan leads. Basic crimping and soldering skills are required.
Q: Can I run fans that draw more than 40 amps each?
A: No. Each circuit is rated to 40 amps and the connectors to 46. Verify your fan draw under sustained load rather than inrush, and fuse accordingly.
Q: Where do I ground the fans?
A: The two black wires carry the fan negatives and share one ring terminal. Bolt it to clean bare metal on the frame or unibody near the fans, not to a bracket or a painted panel. The full fan current returns through that point, so a poor ground costs you airflow the same way undersized wiring does. If your body-to-frame or body-to-engine bonds are tired, add one of our BGC body ground cables.
Q: What is the 4-way connector set for?
A: It is an optional sealed disconnect for the four relay coil wires, so you can unplug the harness from your switch or controller without cutting anything. Both coil pairs pass through the one connector. If you do not want a disconnect, leave it in the bag — nothing else in the kit depends on it.
Q: Can I shorten the output wires?
A: Yes. The 12 ft output legs are supplied pre-stripped and can be trimmed to suit your routing. Keep runs as short as practical to minimise voltage drop.
Warranty & Support
Racetronix harnesses are considered the standard by which others are judged. Every harness is assembled using our computerized crimp-quality monitoring system and then circuit checked before it ships.
This kit is backed by our Limited Lifetime Warranty to the original purchaser while installed in the original vehicle. Warranty claims are subject to proper electrical diagnosis — part-swapping is not a substitute for troubleshooting.
How to get technical support
Racetronix provides technical support to verified customers through our support forum rather than by phone or email. Request access as soon as you place your order. Approval is handled while your parts are in transit, so the documentation and the people are already there on the day you start the install.
We concentrate support in one place for good reasons:
- Open around the clock. Answers do not wait for business hours or for someone to be free at a desk.
- Knowledge going back to 1999. Installation threads, schematics and diagnoses accumulated since we started, all searchable.
- Moderated and approval-only. No spam and no noise — just customers and our technical staff.
- No attachment limits. Post full-resolution photos of your own wiring and get an answer against what you are actually looking at, instead of a description of it.
- Answers stay available. A solution posted once helps the next person with the same vehicle.
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