Geotab HRN-INTX21ATC Harness

← All Geotab harnesses

What Is the HRN-INTX21ATC?

The HRN-INTX21ATC is a fuse interrupter harness that plugs into a vehicle's standard ATC fuse position so the Geotab Relay Kit can open and close that fused circuit for starter inhibit. Geotab describes it as a way to tap an existing circuit with no permanent vehicle modification.

ATC is the full-size blade fuse, sometimes called a standard blade. Among the four fuse interrupters Geotab lists, this is the only one rated above 30A; Geotab gives the HRN-INTX21ATC a ceiling of 40A. The other three cover smaller fuse bodies, so the choice comes down to which fuse style sits in the slot you plan to interrupt.

Which Vehicles and Devices Does the HRN-INTX21ATC Work With?

Geotab does not tie this part to a vehicle make or year. Its listing ties it to a fuse style instead: any vehicle where the circuit chosen for starter inhibit runs through an ATC fuse is a candidate. The partner product is the Geotab Relay Kit, and the purpose Geotab names is starter inhibit.

In Geotab's starter inhibit guide for its relay kit, the relay is driven by an IOX-OUTPUTM plugged into the expansion port of a GO9 that is itself installed with a T-harness. That guide covers internal combustion vehicles only and warns against fitting starter inhibit to hybrid, plug-in hybrid, mild hybrid, battery-electric vehicles or motorcycles. Geotab's relay kit documentation also rules out push-button start vehicles.

Geotab lists no superseded part and no required companion harness for it.

What Problem Does It Solve on the Job?

The classic starter inhibit install means finding the cranking wire with a meter, cutting it, and soldering the relay harness into both ends. On leased trucks or units headed for resale, many fleet managers do not want factory wiring cut at all. A fuse-slot interrupter avoids that.

The 40A rating matters on older work trucks and equipment where the circuit that feeds the start function is protected by a larger ATC fuse. A 30A-rated interrupter is not an option in a 40A position. Before we quote a starter inhibit job, we look at the actual fuse in the slot, read its rating, and match the interrupter to it.

How Is the HRN-INTX21ATC Installed?

Geotab's specific install item for this part is hosted in its install guide library, and our technicians work from it on site. The general sequence for a starter inhibit job, drawn from Geotab's relay kit guide, runs like this:

1. Park the vehicle securely, key off. Disconnect the GO device before relay work begins, as Geotab's relay kit document instructs.
2. Use wiring diagrams to confirm which fused circuit controls cranking, and check that it is not multiplexed and does not feed anything that keeps the engine running.
3. Pull the ATC fuse from that position and fit the HRN-INTX21ATC in its place, per Geotab's listing that the part replaces an existing ATC fuse.
4. Connect the interrupter to the relay kit, wire the relay's ignition feed to a true ignition source with a fuse, and ground as the kit instructions direct.
5. Reconnect the GO device, secure it and every harness with cable ties, and confirm it powers up and reports in MyGeotab, then complete the record in MyInstall.
6. Run Geotab's inhibit tests: the engine must not crank with the relay energised, must crank when it is released, and must keep running if the relay energises mid-run.

Two general Geotab harness rules still apply to the GO device side: total harness length cannot exceed 2 m (6.5 ft), and two T-harnesses are never chained together.

Which Related Harnesses Should You Compare?

• HRN-INTX2S1MINI: the same job for Mini blade fuses, rated to 30A.
• HRN-INTX2S1LPM: sized for Low-Profile Mini fuses that sit nearly flush in the box, rated to 30A.
• HRN-SIFUSETAP: a fuse tap that powers the starter inhibit relay from an existing fuse, used together with a compatible interrupter.
• HRN-CX10S4: a relay harness for IOX-KEYLESS that uses the cut-and-solder starter wire method instead of a fuse slot.

What Are Common Questions About the HRN-INTX21ATC?

Does the HRN-INTX21ATC require cutting the starter wire?

No. Geotab describes it as a way to tap an existing ATC fuse circuit with no permanent change to the vehicle, which is the whole reason to choose it over a cut-and-solder relay install.

What fuse size does the HRN-INTX21ATC handle?

Geotab lists it for ATC, also called standard blade, fuses rated up to 40A. If the slot you want holds a Mini, Low-Profile Mini or Micro2 fuse, a different INTX part is needed.

Can the HRN-INTX21ATC be used on a push-button start vehicle?

Geotab states its relay kit cannot be used on push-button start vehicles, so this interrupter is meant for bladed-key starts. We confirm the ignition type during our pre-install survey.

API Signal supplies and installs Geotab harnesses, relay kits and GO devices on site at your yard, drawing on 35 years of twelve-volt work. Call 803-513-1009 or use Get a Quote and we will match the right fuse interrupter to each vehicle before the install day.

Sources: Geotab Harness Identification and Application; Geotab SPR-RELAYKIT; Geotab Starter Inhibit guide, IOX-OUTPUTM & SPR-RELAYKIT. GEOTAB is a registered trademark of Geotab Inc. API Signal is an independent installer and is not Geotab.