Webasto HVH50
The Webasto HVH series are electrical water heaters typically used in popular PHEV.
Connectors
The HV connector is a Tyco HVA280 connector with A-key (might be different on other devices).
The small center pins are for interlock (detect that the connector is seated). The right pin (with tab facing upwards) is HV+, the left one HV-
The LV connector is best found by the VW part number 1J0973714
Pin 1 is permanent 12V
Pin 2 is an analog output
Pin3 is an analog or PWM input
Pin 5 and 7 are interlock (probably must be shorted)
Pin 6 is LIN
Pin 4 and 8 are unused
Ground must be connected the the case via a stud.
Communication & Control
While there is a document describing the LIN interface , Webasto seems to have altered the interface for different OEMs. According to the document, LIN bus speed is 19200 but on a unit obtained from ebay it was 9600. So always try both.
The data format seems common as follows
| Command | Possible IDs | Byte 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
|---|---|---|---|---|---|---|---|---|---|
| Write power | 35 | 0=Off, 1=On | Temp setpoint
1 digit=1 degree Offset -40 |
Power limit
1 digit=40W |
- | - | - | - | - |
| Read Status | 24 or 23 | various | status | info | |||||
| Read Meas | 40 or 22 | Lin status
0=good, 1=issue |
Outlet temp
Scaling as above |
Inlet temp | HV value MSB | HV value LSB | Power MSB | Power LSB
1 digit=20W |
Some units allow control via a simple on off signal on Pin 3 (12V=heat up liquid to 85°C) and some units allow a strange PWM control between 50-100Hz where 25%-81% duty cycles allow setting various power levels.