Geotab HRN-RW03K5 Harness

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What Is the HRN-RW03K5?

The HRN-RW03K5 is a pulse harness kit that lets a Geotab GO RUGGED detect a running engine on equipment that reports neither ignition status nor RPM. It does this by connecting to the low-voltage, or primary, side of the engine's ignition coil, where the coil switches on and off with every firing cycle.

Think of an older gasoline forklift, a towable generator, or a baggage tug powered by an industrial spark-ignition engine with no electronic control module. There is no data port to read and often no dependable key-on wire. Yet the coil is working every time the engine runs, and that activity is a signal the device can use. Geotab sums up the purpose as non-ECM equipment with no true ignition, and lists the harness as required for ground service equipment.

Which Vehicles and Devices Does the HRN-RW03K5 Work With?

The kit is part of Geotab's GO RUGGED range and pairs with that sealed device. Its natural home is spark-ignition equipment with a conventional coil and no engine computer reporting RPM. In Geotab's GO9 RUGGED notes, the pulse harness sits in the short list of harnesses needed for ground service equipment, next to the HRN-RW04K4 differential harness and the Kubota and Ford EDI engine harnesses.

Geotab lists the kit contents as the HRN-RW03S5 harness plus a fuse kit, with no part replaced and no separate base harness named. At 122 cm (48 in), this is one of the longer rugged harnesses, which leaves less than a metre of room under the 2 m total cable limit. That matters when the coil sits at the front of an engine bay and the best mounting point for the device is on the frame or behind a seat.

What Problem Does It Solve on the Job?

An equipment manager running a mixed yard of older gas units usually wants two things from telematics: where each machine is, and how many hours it actually ran. Location is easy. Run hours are not, because a key switch left on or a battery charger connected can fool a simple voltage-based install. The coil only pulses when the engine is turning, so reading it ties hour counts to real engine activity rather than to the position of a switch.

Hour accuracy drives maintenance schedules and rental billing. A towable light tower billed by the hour, or a forklift serviced every few hundred hours, needs a number the owner can trust. On these engines, the pulse harness is how we get that number without adding a separate sensor.

How Is the HRN-RW03K5 Installed?

Geotab publishes installation instructions for this kit. The outline below follows Geotab's rugged installation rules:

1. Note the device serial number, the asset name and the current hour meter reading, and register the serial before touching the machine.
2. Shut the engine off and keep the GO RUGGED disconnected while you work on the harness.
3. Locate the ignition coil and identify its primary terminals, the low-voltage side fed by the ignition circuit. Leave the high-voltage tower and plug leads alone.
4. Connect the pulse lead and the power leads as the Geotab instructions describe, using the supplied fuse kit and sealed connections.
5. Route the harness away from exhaust manifolds, belts and the high-voltage leads, keeping the total run within 2 m (6.5 ft). Do not join two T-harnesses.
6. Mount the device to a solid surface with a view of the sky and tie the harness down at both sides of every joint.
7. Start the engine, wait for the status LEDs to settle, and confirm a Pass result in MyInstall before releasing the machine.

Which Related Harnesses Should You Compare?

• HRN-RW04K4: the differential option that reads an oil pressure switch or works with a negative-side disconnect.
• HRN-RW03K4-A: the rugged three-wire kit when the machine has a proper ignition wire to tap.
• HRN-RZ04T4: the Kubota engine harness for ground service units built on Kubota power.
• HRN-RZ04T41: the Ford EDI tug T-harness for the MSG-425 engine.

What Are Common Questions About the HRN-RW03K5?

Which side of the ignition coil does the HRN-RW03K5 use?

Geotab specifies the low-voltage side, also called the primary side. The high-voltage output that feeds the spark plugs is never the connection point.

Does a diesel machine need the HRN-RW03K5?

The harness is built around an ignition coil, which a diesel engine does not have. For a diesel with no usable ignition signal, we look at the HRN-RW04K4 oil pressure option instead.

What comes in the HRN-RW03K5 kit?

Geotab lists the kit as the HRN-RW03S5 harness together with a fuse kit. The harness is 122 cm (48 in) long.

With 35 years in twelve-volt work behind us, API Signal supplies the Geotab harness and device and fits both on site, older gas equipment included. Phone 803-513-1009 or request pricing on Get a Quote.

Sources: Geotab harness identification, Geotab pulse harness installation instructions, Geotab GO9 RUGGED, Geotab GO9 RUGGED installation guide. GEOTAB is a registered trademark of Geotab Inc. API Signal is an independent installer and is not Geotab.