Vehicle Temperature Services

This page explains how vehicle temperature data is reported through the Fleet API, covering the available temperature sources, which endpoints to use for different use cases, and how temperature alerts are delivered.

Temperature Sources

The Fleet API exposes two categories of temperature data:

Category	Fields	Where it comes from
Cargo / cabin temperature probes	temp1, temp2, temp3, temp4	Up to four external temperature sensors wired to the Cartrack device, commonly used for refrigerated transport and cold chain monitoring
Engine and unit temperatures	water_temp (coolant), oil_temp, unit_temp	Read from the vehicle's CAN bus (coolant and oil) or from the Cartrack device itself (unit temperature)

All temperature values are returned in Celsius as decimal numbers. A field is null when the corresponding sensor is not fitted or not reporting.

warning

Temperature sensor availability depends on the hardware installed in the vehicle. If no temperature probes are fitted, the temp1 to temp4 fields return null. Contact your Cartrack account manager if you are unsure which sensors are installed on your fleet.

Which Endpoint Should I Use?

Use this mapping based on what you want to accomplish:

Goal	Endpoint
Get the latest temperature reading for all vehicles	Get Vehicles Temperature Data
Get historical temperature readings for a period	Get Vehicles Temperature Data
Get temperature together with position, fuel, and odometer in one call	Get Vehicles Status
Get engine coolant and oil temperature per event	Get Events for All Vehicles / Get Events for One Vehicle
Retrieve triggered temperature alert notifications	Get Alerts Notifications

1) Dedicated Temperature Endpoint

What It Means

GET /topics/vehicles/temperature is the recommended endpoint for temperature monitoring. It returns the readings from the four temperature probes for all vehicles in the account, and operates in two modes:

• Latest mode: omit both filter[start_timestamp] and filter[end_timestamp] to get the most recent temperature reading per vehicle, provided data was reported within the last 2 months.
• History mode: provide a time range to get all readings within it. The range is limited to a maximum 24-hour period. If only one timestamp is given, the other defaults to 24 hours before or after it.

Use filter[registration] to restrict the response to a single vehicle.

Response Fields

Field	Type	Description
vehicle_id	integer	Cartrack vehicle identifier
registration	string	The vehicle's registration
temp1 to temp4	number or null	Temperature reading from sensors 1 to 4, in Celsius
event_ts	string	When the reading was recorded by the device
recieved_ts	string	When the reading was received by Cartrack

If recieved_ts is significantly later than event_ts, the vehicle was likely in an area with poor network coverage and the data was transmitted with a delay. Keep this in mind when monitoring time-sensitive cold chain thresholds.

Sub-User Access

This endpoint supports Topic-Based Access Control. Grant the TEMPERATURE topic to a sub-user to give it the same temperature data access as the account administrator, without exposing the rest of the account.

Developer Considerations

• History queries are limited to 24 hours per request. For longer periods, issue multiple requests with consecutive windows.
• Results are paginated: use the page and limit parameters to iterate through large fleets.
• In latest mode, vehicles that have not reported temperature data in the last 2 months are not returned.

2) Temperature in Vehicle Status

GET /vehicles/status includes the temp1 to temp4 fields as part of each vehicle's last known state, alongside position, ignition, fuel, and odometer. This is a point-in-time snapshot, not a history.

Use it when you already poll vehicle status for a live dashboard and want to display current temperatures without an extra API call.

3) Engine Temperatures via Events

The events endpoints (GET /vehicles/events and GET /vehicles/{registration}/events) return the full event stream from the vehicle. Each event includes the probe readings plus the engine-related temperatures:

Field	Description
temp1 to temp4	Temperature probes 1 to 4, in Celsius
water_temp	Engine coolant temperature, in Celsius
oil_temp	Engine oil temperature, in Celsius
unit_temp	Internal temperature of the Cartrack device, in Celsius

Engine coolant and oil temperatures depend on CAN bus support for the vehicle model and return null when not available.

4) Temperature Alerts

Temperature-related alerts are configured on the account (through Fleetweb or your Cartrack account manager) and can then be retrieved through the API:

1. Call Get Alerts Notification Types to list the alert types available on your account. Temperature-related types include COOLANT_TEMPERATURE, ENGINE_TEMPERATURE, TEMPERATURE_DIAGNOSTIC, and the geofence-scoped probe alerts GEOFENCE_ALERTS_TEMP1_HIGH_WITH_IGNITION_ON to GEOFENCE_ALERTS_TEMP4_LOW_WITH_IGNITION_ON (a high and a low variant per probe).
2. Call Get Alerts Notifications with filter[alert_type] set to the relevant type to retrieve the triggered notifications for a period (limited to 31 days per request).

info

Creating temperature alerts through the API is not currently supported. The alert creation endpoints cover other alert types (geofence, ignition, and PTO and panic sensors); temperature thresholds are configured on the account itself.

Recommended Integration Pattern

1. For cold chain monitoring: poll GET /topics/vehicles/temperature in latest mode at your refresh interval, and compare temp1 to temp4 against your thresholds. Check event_ts to make sure the reading is recent before acting on it.
2. For temperature history and auditing: pull GET /topics/vehicles/temperature with consecutive 24-hour windows and store the readings on your side.
3. For live fleet dashboards: read the temp1 to temp4 fields from GET /vehicles/status, which you likely already poll for positions.
4. For threshold breach notifications: configure temperature alerts on the account, then poll GET /alerts/notifications filtered by the temperature alert types.
5. For engine health monitoring: use the events endpoints and track water_temp and oil_temp over time.