Three wires, and what they give away.
The Wired unit cannot see the engine. It gets a permanent feed, a ground and the ignition line, and it turns out a vehicle's electrics are an honest witness. An alternator cannot pretend the engine is off. A battery cannot hide being replaced.
- SAR 290
- Once, per vehicle
- 45 minutes
- With a certified fitter, at your yard
- 9–36 V
- Vans, trucks and plant on one unit
- 13 hours
- Live on its own cell, or 20 days parked
One day on TRK-207, read off the wires
Composed rather than recorded: no truck manages all of this in a day. Pick a rule and see every minute it owned. Of the 10 events worth writing down, 4 needed a person, 3 belonged to the workshop, and 3 were the unit noticing on your behalf.
Engine running, ignition line off
Needs a personcharging ≥ 27 V · ignition offThe alternator says the engine is running and the ignition wire says it is not. Either the wire has failed or it has been bypassed — and a trip taken like this never appears as a trip.
Then: Book the vehicle in to check the ignition line.
- 09:05–09:48 · 43 min
The supply voltage is the engine's alibi
Every rule above rests on four numbers. They are ordinary lead-acid electrics, and a 24-volt truck is two 12-volt batteries in series, so one set of figures doubles into the other.
Newer alternators move their charging voltage around to save fuel, and battery sizes vary, so the unit spends its first week on a vehicle learning that vehicle's own numbers. Voltage alerts in that week are marked provisional.
| Reading | 12 V van | 24 V truck |
|---|---|---|
| Charging The engine is running. Nothing else on a vehicle holds the supply this high. | ≥ 13.5 | ≥ 27.0 |
| Healthy at rest Settled for an hour with everything off, on batteries that are fine. | 12.6 | 25.2 |
| Resting low Settled, and short of what healthy batteries rest at. A hint on its own. | < 12.3 | < 24.6 |
| Weak crank How far the supply sags while the starter turns. The hint confirmed. | < 9.5 | < 19.0 |
The unit runs from 9 V to 36 V. A weak crank on a 12-volt van dips to within 0.5 V of that floor, and past it the unit carries itself through the start on its own cell.
When somebody takes the power away
The unit carries a small cell of its own, sized for a disconnection rather than a working life. Moving, it reports live for 13.3 hours. Parked, it checks in hourly for 20 days.
The cell refuses charge above 45°C, and a parked cab in summer passes that by mid-morning. It charges when the air conditioning runs, which is to say when the truck is working. The figures here assume it started the day full.
- Today, on the cell
- 2.6%
- 314 minutes disconnected and 12 minutes being towed used 21 of its 800 mAh.
- Left connected, parked
- 1.5%
- Of a 180 Ah pair of truck batteries over 14 days, at 8 mA. Not the reason a truck will not start.
- Two switch inputs
- Usually a rear door, because a door opening away from a delivery point is the one signal that catches a load going missing, and a PTO or tipping body, for the hours an engine spent working something other than the wheels. Anything past two is the Advanced unit's four.
No standard place to look
Each fitter chooses a spot behind the trim for that vehicle, photographs it, and the photograph goes on the vehicle's record. The next fitter can find it in a minute. Nobody else in the yard learns where the tracker is, because across forty trucks there are forty answers.
The case reports being opened. Opening it still takes a person the unit cannot argue with, which is why the rules above care more about what the power and ignition do next than about the case itself.
What three wires cannot tell you
Anything the engine knows
No fault codes, no fuel level, no engine temperature. The maintenance page is built on the engine bus, so on a light vehicle that is the OBD unit's SAR 170 more, and on a truck it is the Advanced.
Distance comes from the sky, not the gearbox
Our distance and the dashboard's will disagree by a few percent, and dashboards are built to over-read. Once we have seen both on a vehicle we offset it, so service reminders land where the sticker says.
The first week is provisional
Until the unit has learned a vehicle's own charging and resting voltages, the battery and ignition rules run on the textbook figures in the table, and they are wrong often enough that we say so on every alert.
Concealed is not invisible
Someone who knows what they are looking for will find it. The day above ends that way on purpose, and the security page is blunt about who this catches and who it does not.