Mastering Geotab
★ Geotab Harnesses · GO9 RUGGED Harnesses
The HRN-RW04K4 is Geotab's differential harness kit for the GO RUGGED, used where a machine has a negative battery disconnect, an oil pressure switch or a negative ignition output. Geotab requires it for ground service equipment.
The HRN-RW04K4 is a differential harness kit for the Geotab GO RUGGED that handles three awkward signal situations: a negative battery disconnect, an oil pressure switch, or an ignition output that switches negative. The kit includes the HRN-RW04S4 harness plus a fuse kit, and the harness measures 100 cm (39 in).
Most telematics wiring assumes one battery wire, one ignition wire and a frame ground. Airport ramp equipment and older industrial machines often break those assumptions. A baggage tractor may cut the negative cable rather than the positive one. A belt loader may have no engine computer at all and no clean ignition lead to tap. Geotab built this harness for exactly those machines, describing its purpose as equipment with a ground disconnect, or non-ECM equipment that lacks a true ignition.
The kit is made for the GO RUGGED, the sealed Geotab unit rated IP68 and IP69K that bolts onto equipment outside the cab if needed. Geotab names three use cases: a negative battery disconnect, an oil pressure switch, and a negative output ignition. In its GO9 RUGGED documentation, Geotab lists this harness among those required for ground service equipment, alongside the HRN-RZ04T4, HRN-RZ04S4 and the RW03 pulse harness.
No earlier part is listed as replaced by this kit, and no separate base harness is named as a prerequisite. The maximum connected cable remains 2 m, so the 100 cm harness leaves roughly a metre of budget for anything else in the run.
One upgrade warning matters here. Geotab strongly advises that any 12 or 24 volt vehicle moving from a GO8 or older device to a GO9 or newer device have its cable harness replaced with an approved version, and it keeps a list of the affected harnesses. Ramp fleets often mix hardware generations, so we check every unit.
On a ramp, the questions are utilisation and engine hours. How many tugs actually ran on the overnight shift? Which belt loader is due for service? On a machine with no ECM data and no true ignition, a basic three-wire install can guess wrong, logging the unit as idle when it is working or as running when it is parked with a switch left on.
The oil pressure option is a practical answer for simple engines. Oil pressure only builds when the engine turns, so a pressure switch gives a running signal that a key position cannot fake.
Geotab publishes installation instructions for this harness, and its rugged install rules apply throughout. Our technicians follow that sequence on every unit:
| Spec | Detail |
|---|---|
| Part number | HRN-RW04K4 |
| Type | Differential harness kit |
| Kit contents | HRN-RW04S4 harness and fuse kit |
| Compatible device | GO RUGGED (GO9 RUGGED) |
| Use cases | Negative battery disconnect, oil pressure switch, negative output ignition |
| Equipment class | Required for ground service equipment |
| Harness length | 100 cm (39 in) |
| Maximum connected cable | 2 m |
| Country of origin | China |
| Upgrade note | Replace older cable harnesses with an approved version when moving from GO8 or older to GO9 or newer |
Decide which signal you are using before cutting anything, because the three cases wire differently and mixing them up gives false engine hours. Oil pressure switches on older engines can be weak or intermittent, so watch the reading at idle as well as under load. Ramp equipment gets pressure washed and sits in rain and de-icing spray, so seal every splice and keep the device away from exhaust heat. If a fleet runs both 12 and 24 volt units, label each install so the next tech knows what was done.
Much ground service equipment has no engine computer and no true ignition wire, so the GO RUGGED needs another reliable signal. Geotab lists this harness as required for that equipment class.
No. Geotab lists the HRN-RW04S4 as part of the HRN-RW04K4 kit, together with a fuse kit.
Geotab strongly advises replacing the cable harness with an approved version when moving 12 or 24 volt vehicles from GO8 or older units to GO9 or newer. We swap the harness as part of the upgrade.
Our crew brings Geotab harnesses and devices to your site and fits them on the equipment where it is parked, ramp fleets included. Reach API Signal at 803-513-1009 or send the details through Get a Quote.
Sources: Geotab harness identification, Geotab differential harness guide, 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.
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