Air Conditioning

This documentation covers the Caravan LIN Protocol for Truma air conditioning units including Aventa Comfort, Aventa Eco, Aventa Compact, Saphir Compact, and Saphir Comfort RC models.

Frame Overview

Truma air conditioning units communicate using two primary LIN frames:

Supported Devices

The following Truma air conditioning units are known to use this protocol:

Note: Variant ID may vary depending on hardware revision and production date. The Function ID is the primary identifier for device type.

Light Support Detection

Light support is determined from the variant_id field in the diagnostic response:

Example: variant_id = 0x00 → has light; variant_id = 0x01 → no light.

Control Frame (ID 0x08) - Commands to Truma AC

Frame Format: [ID=08] [E0] [05] [72] [05] [FF] [FF] [32] [FF]

The control frame sends commands to the Truma air conditioning unit to set target temperature, operating mode, fan speed, and light brightness.

Bytes 0-1: Target Room Temperature

16-bit value (little-endian)

• Format: 0.1°C resolution with -273°C offset
• Calculation: Temperature = (Raw Value × 0.1°C) - 273°C
• Range: 0x0B4A - 0x0BE0 (16.0-31.0°C)

Encoding Example:

Bytes:  [0x8A] [0x0B]
Value:  0x0B8A = 2954 decimal
Temp:   (2954 × 0.1) - 273 = 22.4°C

Important: The target temperature is only accepted by the AC unit when an active operating mode (Fan, Cool, Heat, or Auto) is set in the climate mode byte (Byte 3). When the climate mode is “Off” (0x00), the target temperature is ignored.

Byte 2: Fan Mode

Fan speed control

Byte 3: Climate Mode

Operating mode control

Fan Mode Compatibility by Aircon Mode

Available fan modes vary depending on the climate mode and device model:

Legend: L=Low (0x71), M=Mid (0x72), H=High (0x73), N=Night (0x74), —=Not available

General Rules for Fan Mode Combinations

• Night (0x74) is ALWAYS exclusive to Cool (0x05)
• Standard combination = Low, Mid, High
  • Exceptions: Fan mode on Eco/Saphir Compact: no Mid
  • Exceptions: Heat mode on Aventa Comfort: no Mid
• Models without Heat function have no Mid in Fan mode (except Aventa Compact)

Bytes 4-5: AC Power / Reserved

16-bit value (little-endian)

The meaning of these bytes depends on the model:

AC Power (1W/bit) for the following models:

• Aventa Comfort (before 01/2019)
• Aventa Eco
• Saphir Compact
• Saphir Comfort RC

0xFF for the following models:

• Aventa Comfort (from 01/2019)
• Aventa Compact
• Aventa Compact Plus

Byte 6: Light Brightness

Interior light control (if supported by device variant)

• Encoding: 1% per bit
• Range: 0-100 (0x00-0x64)
• Steps: Only 4% steps are valid
• Values:
  • 0x00: Light off (0%)
  • 0x10: Lowest ON setting (16%)
  • 0x14, 0x18, 0x1C, …: Further steps in 4% increments (20%, 24%, 28%, …)
  • 0x64: 100% brightness (full)
  • 0xFF: Light not available/not used

Note: Light control is only available on devices with variant ID 0x01. Set to 0xFF for devices without light support (variant ID 0x00). Valid values are only 0 (OFF) and 16-100 in 4% steps.

Byte 7: Reserved

Always 0xFF

This byte is reserved and must be set to 0xFF.

Info Frame (ID 0x17) - Status from Truma AC

Frame Format: [ID=17] [6C] [0B] [00] [00] [00] [C0] [00] [FF]

The info frame reports the current status of the Truma air conditioning unit, including actual room temperature, target settings, operating mode, and error status.

Bytes 0-1: Actual Room Temperature

16-bit value (little-endian)

• Format: 0.1°C resolution with -273°C offset
• Calculation: Temperature = (Raw Value × 0.1°C) - 273°C

Decoding Example:

Bytes:  [0x6C] [0x0B]
Value:  0x0B6C = 2924 decimal
Temp:   (2924 × 0.1) - 273 = 19.4°C

Bytes 2-3: Target Room Temperature

16-bit value (little-endian)

• Format: Same encoding as actual temperature
• Range: 0x0B4A - 0x0BE0 (16.0-31.0°C)
• Special Value: 0x0000 (-273°C) indicates system off / no target set

Example:

Bytes: [0x00] [0x00]
Value: 0x0000 = System OFF (no target temperature)

Important: The target temperature is automatically reset to 0x0000 when the AC unit is turned off (climate mode = Off). A valid target temperature is only displayed when an active operating mode (Fan, Cool, Heat, or Auto) is active.

Byte 4: Fan Mode

Current fan speed setting

Byte 5: Climate Status

Bit-encoded status byte

Bits 0-3: Current Climate Mode

Bits 4-7: Reserved

Byte 6: Light Brightness

Interior light control status

• Range: 0-100 (0x00-0x64)
• Unit: Percentage brightness
• Values:
  • 0x00: Light off (0%)
  • 0x32: 50% brightness
  • 0x64: 100% brightness (full)
• Resolution: 1% increments

Byte 7: Reserved

Always 0xFF