Truma Combi Service Handbook

The Blue Pages: 12VDC
Component Measuring points Function/Setpoint Remark
Input fuse F1 Switch off the appliance, remove the
fuse and check for continuity
Continuity (0 Ω) Replace fuses only with similar
fuses.
Air temperature switch Pull out the X19 plug
Continuity between
X19-3 and X19-4 (on plug)
Continuity (0 Ω) The switch must be closed
Opens at 374°F/190°C
Water temperature switch
Pull out the X18 plug
Continuity test between
X18-3 and X18-4 (on plug)
Continuity (0 Ω) The switch must be closed
Opens at 185°F/85°C
Room temperature sensor
cable
Detach the cable from the room
temperature sensor and the
electronics and check the continuity
of both wires
Continuity (0 Ω) If there is no continuity, replace
the cables
Component Measuring points Function/Setpoint Remark
Water temperature sensor Pull out the X18 plug
Resistance measurement between
X18-1 and X18-2 (on plug)
68°F / 20°C = 12.5 kΩ
77°F / 25°C = 10.0 kΩ
104°F / 40°C = 5.3 kΩ
122°F / 50°C = 3.6 kΩ
Resistance value (NTC)
is temperature-related
Air temperature sensor Pull out the X19 plug
Resistance measurement between
X19-1 and X19-2 (on plug)
68°F / 20°C = 125 kΩ
77°F / 25°C = 100 kΩ
122°F / 50°C = 36 kΩ
176°F / 80°C = 12 kΩ
Resistance value (NTC)
is temperature-related
Room temperature sensor Pull out X10 and X11 plugs
Resistance measurement between
X10 and X11 (on plug)
59°F / 15°C = 15.7 kΩ
68°F / 20°C = 12.5 kΩ
77° F / 25°C = 10.0 kΩ
Resistance value (NTC)
is temperature-related
The furnace will not operate in
case of a short circuit or
interruption.
Solenoid coil “small”
Pull-in winding
Pull out X7 plug
Resistance measurement between
X7-18 and X7-20 (on plug)
8-9 Ω If the resistance value is
outside, replace the coil
Solenoid coil “small”
Hold-in winding
Pull out X7 plug
Resistance measurement between
X7-18 and X7-19 (on plug)
310-340 Ω If the resistance value is
outside, replace the coil
Solenoid coil “large”
Pull-in winding
Pull out X7 plug
Resistance measurement between
X7-15 and X7-17 (on plug)
8-9 Ω If the resistance value is
outside, replace the coil
Solenoid coil “large”
Hold-in winding
Pull out X7 plug
Resistance measurement between
X7-15 and X7-16 (on plug)
310-340 Ω If the resistance value is
outside, replace the coil
Combustion air temperature
sensor
Pull out X7 plug
Resistance measurement between
X7-6 and X7-7 (on plug)
68°F / 20°C = 12.5 kΩ
77°F / 25°C = 10.0 kΩ
104°F / 40°C = 5.3 kΩ
122°F / 50°C = 3.6 kΩ
Resistance value (NTC) is
temperature-related
Continuity
Resistance

Truma Combi Specifications

General

Type	Combination heater
Fuel	LPG
Water capacity	10 liters
Control	Digital control panel
Safety Features	Overheat protection, flame monitoring
Efficiency	Up to 90%