Truma Combi How to use

Truma Combi
Service Handbook

Before Working on a Truma…
Warranty Period and Registration:
Truma systems are covered through Truma’s Manufacturer Limited Warranty as defined at www.truma.net and the Truma
Terms & Conditions of sale.
Truma systems come with a 12 months (parts and labor) Limited Manufacturer Warranty and can be extended to 24 months
(parts and labor) upon Warranty Registration within 60 days of purchase.
Warranty Registration can be handled via the warranty post card enclosed in the manuals supplied with the Truma system, or
at www.truma.net.
Service and Warranty Claims:
Before working on a Truma system: All service and warranty related inquiries, including troubleshooting, involving Truma
systems must be directed to the Truma Service Department at: [email protected] or by calling 855-558-7862 ext. 1.
*** Please include the model and serial number of the Truma system in question with all inquiries.
If the Truma Service Representative is unable to support in finding a resolution to the issue, they will provide you a Warranty
Claim Number if the unit is within the Warranty Claim period and the following steps must be followed:
•Please send an order to [email protected] referencing the warranty claim number. Truma will send you an order
confirmation.
•The Truma Service Representative will send you the Warranty Claim Form (WCF) and a Returned Material
Authorization (RMA) if parts need to be returned.
•Complete the Warranty Claim Form as per the instructions.
•The Warranty Claim Form is to be placed with the returned components.
•To ensure that the end user bought the Truma system at a certified Truma Service Partner within the warranty time frame,
a copy of the purchase receipt must be included with the returned components. If the Truma appliance was sold with the
RV, a copy of the first registration is required.
•All returned components are to be returned in their original packaging to avoid further damage.
•Returned components are to be shipped to the destination indicated on the RMA or as instructed by the Truma Service
Representative.
•The RMA is to be affixed to the outside of the packaging for all returns.
•If the Truma Claims process determines product is defective, reasonable shipping charges will be reimbursed.
Components need to be received within 45 days to allow for processing of the Warranty claim and issuance of credit.
•WCF will be evaluated by the Truma Service Department and disposition raised for credit.
Sales Return:
•If you have ordered the wrong product(s) or the wrong quantity and
you want to return it to Truma, please contact your Account Manager
or email [email protected] to ask for an RMA.
•All returned components are to be returned in their original packaging
to avoid further damage.
•Returns are subject to the Truma Terms and Conditions of sale.
•Returned components are to be shipped to the destination indicated
on the RMA or as instructed by the Truma Representative.
•The RMA is to be affixed to the outside of the packaging for all returns.
•Please use one RMA for each carton and place in a visible location.
•Please note that the returned products will only be accepted by Truma
if such returned item is in its original packaging, is a Product of a current product line and both packaging and product are
undamaged. Damaged packaging or product will get deducted to the credit note by the amount of additional labor and
spare parts costs to replace it. Any returned and accepted product will be subject to a re-stocking fee as outlined in the
Truma Terms and Conditions.
Label Example: Combi

Description & Technical Data
With more than 20 years of reliable service in Europe and Australia, Truma Combi furnaces are
the most energy-efficient and lightest heating systems on the market. Truma Combi heaters
combine two functions in one appliance. They warm the living area and heat water in the
integrated stainless steel tank. Depending on the model, Truma Combi heaters can be used in
gas, electric, or mixed mode.
Fuel: LP gas (propane only)
Inlet pressure: 11-13”WC. (27.4-32.4mBar)
Manifold pressure: 10”WC (24.9mBar)
Duct static pressure: minimum of 0.00”WC (0.0mBar)
maximum of 0.65”WC (1.6mBar)
Temperature rise: <150⁰F (83⁰C)
Energy Input Rate / Gas Consumption
LP gas mode Operating Level 1 Operating Level 2 Operating Level 3
Combi eco 7,500BTU/hr (2.2kW) 14,300BTU/hr (4.2kW) --
Combi eco plus 5.3oz/h (150g/h) 10oz/h (290g/h)
Combi comfort 7,500BTU/hr (2.2kW) 14,300BTU/hr (4.2kW) 20,400BTU/hr (6kW)
Combi comfort plus 5.3oz/h (150g/h) 10oz/h (290g/h) 14oz/hr (410g/h(
Electric mode
Combi eco plus 850W 1,700W --
Combi comfort plus
Mixed mode LP gas + electric
Combi eco plus (max) 7,500 BTU/h (2.2kW) + 1,700W
Combi comfort plus (max) 14,300 BTU/h (4.2kW) + 1,700W
Power Supply
Power consumption at 12VDC (DC < 1Vpp)
Combi eco transient: max. 6.1A (average power consumption: approx. 1.6A)
Combi eco plus transient: max. 6.1A (average power consumption: approx. 1.6A)
Combi comfort transient: max. 6.1A (average power consumption: approx. 1.8A)
Combi comfort plus transient: max. 6.1A (average power consumption: approx. 1.8A)
Power consumption at 120VAC/60HZ (line connection or sine wave generator)
Operating Level 1 Operating Level 2 Operating Level 3
Combi eco plus 7.1A 14.2A --
Combi comfort plus
Hot Water System
Capacity of water container: 2.64gal (10 liters)
Water heating time from approx. 23 minutes in hot water mode (measured according to
59⁰F (15⁰C) to 140⁰F (60⁰C): (EN 15033)
Water inlet pressure: max. 40.6psi (2.8bar)
System operating pressure: max. 65.25psi (4.5bar)
Shipping weight (without water and without peripheral equipment)
Combi eco 35.1lbs (15.9kg)
Combi comfort
Combi eco plus 37.0lbs (16.8kg)
Combi comfort plus

Component Glossary
1. CP Plus Control Panel : Operation and programming of the Truma Combi is controlled by the CP Plus Control Panel.
Powered by a separate 12VDC source from the Combi and protected with a 1A in-line fuse. Connected to the Truma
Combi PCB by a data cable. A W 255 H error code will be displayed on the CP Plus in the event of a connectivity issue
with the Combi PCB.
2. Gas Connection : 5/8” flared male inlet gas supply connection. Operating inlet pressure: 11-13” WC (27.4-32.4 mBar).
3. Magnetic Gas Valve : Supply gas pressure to the combustion chamber is
controlled and regulated by the magnetic gas valve. Depending on the level of
combustion required, the (2) magnetic gas valve solenoids will open or close to
provide 7,500 BTU, 14,300 BTU, or 20,400 BTU (Comfort models only) of
propane to the combustion chamber. Includes a test nozzle for obtaining manifold
pressure: 9.5-11” WC (23.7-27.4mBar).
4. Combined Inlet for Combustion Air/Outlet for Exhaust : Connection for
Combustion Air Inlet tube (80mm) and Exhaust Outlet tube (55mm). Both tubes
terminate on the sidewall of the RV through the Wall Cowl. Combustion air is
pulled into the Combi and exhaust air is pushed out by the Combustion Air Motor.
A damaged or compromised Exhaust Outlet tube may result in exhaust air mixing
with fresh combustion air, leading to combustion failures. 4

Component Glossary
7. Ignition Plugs : Unlike a “standing pilot” ignition system, the Combi
utilizes a Direct Spark Ignitor (DSI) ignition system, which contains (2)
metal rods that create a spark when voltage is applied. A third metal
rod is the Flame Rectifier, which confirms the presence of flame when
a flame is created. The Ignitors and Rectifier are attached to the Gas
Burner.
8. Combustion Chamber : The Combustion Chamber is where the (3)
ingredients for combustion (air, fuel, and spark) are introduced to
each other to create a flame at the Gas Burner.
9. Flame Tube with Baffle Plate : A tube that surrounds the flame
created by the Gas Burner. The Baffle Plate assists with redirecting
exhaust air back into the Exhaust Outlet.
5. Combustion Air Motor : A variable speed fan motor tasked with providing
one of the key ingredients for combustion: Air. The Combustion Air Motor pulls
in fresh combustion air from outside through the Wall Cowl and Combustion
Air Inlet tube and pushes exhaust air out of the Exhaust Outlet tube and Wall
Cowl. It will change speeds to match the combustion needs of the Combi.
6. Gas Burner : Part of the Flame Tube, located in the Combustion Chamber in
the center of the Combi and surrounded by the Air Heat Exchanger and Water
Container, the Gas Burner is where flame is created when heating in Gas
mode. The Gas Burner heats both air for warming the indoor living space as
well as domestic water.
5
10. Circulation Air Fan : A 10 speed fan
motor that draws air from within the
living space into the Air Heat
Exchanger where it absorbs heat from
the flame of the Gas Burner before
being distributed throughout the
indoor living space via duct work. The
Circulation Air Fan typically won’t run
when the Combi’s primary focus is to
just heat water and not air to warm the
living space. However, it also operates
as a cooling device in the event of
excessive air and/or water
temperatures.
11
12
7
6
10
11. Air Heat Exchanger : Surrounding the Combustion Chamber and housing the Electric Heating Elements (Plus models
only), the Air Heat Exchanger is where heat from the Gas Burner or Electric Heating Elements is absorbed by the passing
air being moved by the Circulation Air Fan before entering the duct system for distribution within the living space.
12. 120VAC Electric Heating Elements (Plus models only) : Imbedded in the Air Heat Exchanger are (2) 120VAC 850W
Electric Heating Elements. Whether in EL1/MIX1 (850W) or EL2/MIX2 (1700W), both Electric Heating Elements are
energized. In addition to 120VAC Electric Heating Elements, Combi Plus models will also feature a 120VAC PCB and a
NEMA 5-20P outlet plug.
13. Warm Air Outlets : Duct work (65mm) connections to the Combi. (4) Warm Air Outlets altogether, though Combi Eco
models may only utilize (3), with one of the bottom outlets blocked off with a blank cover (34310-02).

Component Glossary
14. Stainless Steel Water Container : 2.64gal (10 liter) water
container made of V4A stainless steel. The Water Container
surrounds the Air Heat Exchanger and absorbs heat from the Gas
Burner or Electric Heating Elements (Plus models only) to heat the
water for the domestic water supply. The Combi does NOT feature
instant or on demand water heating technology and thus has a
recovery time, like a traditional water heater, to reach the desired
water temperature setpoint.
15. Warm Water Connection Tube : 12mm connection for Warm
Water Connection with Aeration Valve (34020-00178) to hot water
outlet. Aeration Valve features a gravity fed check valve before the
connection of a clear air tube, with the purpose of ensuring all 2.64
gal (10 liters) are drained from the Water Container when the
Drain Valve is opened. Warm Water Connection with Aeration
Valve must be installed so that the hot water plumbing flows in a
vertical direction while the Aeration Valve is positioned in a
horizontal configuration (see component “K”)
16. Cold Water Connection Tube : 12mm connection for cold water
inlet.
14
15
16
17. Room Air Temperature Sensor : NTC thermistor that tells the Combi the
ambient temperature within the living space by converting temperature to
resistance Ω. Connected to the Combi PCB by a wiring harness. At 77⁰F (25⁰C),
the Room Air Temperature Sensor should register approximately 10K Ω. X10
and X11 wire harness connection points at Combi PCB from RTS are not
polarity sensitive.
18. Casing HDF-Therm : Insulation jacket of the Truma Combi
17
Additional Components
A B
A. Air Temperature Switch(es) : N.C safety switch located in the
Air Distribution Chamber that opens it’s contacts to end the
ignition sequence if it senses temperatures above 374°F (190°C).
B. Air Temperature Sensor : NTC thermistor that informs the PCB
of the temperature within the Air Distribution Chamber by
converting temperature to resistance.
C. Combustion Air Temperature Sensor (Not pictured) : NTC
thermistor that informs the PCB of the temperature within the
Combustion Chamber by converting temperature to resistance.
E
D
D. Water Temperature Switch (All models) : N.C. thermal safety
switch that opens it’s contacts to end the ignition sequence if it
senses temperatures above 185°F (85°C).
E. Water Temperature Switch (Plus models only) : N.C. manually
resettable safety switch that opens it’s contacts to end the
ignition sequence if it senses temperatures above 185°F (85°C).
F. Water Temperature Sensor(s) (Not pictured) : NTC
thermistors that informs the PCB of the temperature within the
Water Container by converting temperature to resistance.

Additional Components
G H
G. Drain Valve (Previous version) : Shown in the “closed” position,
the drain valve is installed on the cold water inlet of the Combi and
is used to drain the Water Container when placed in the “open”
position. In addition to a manual drain, it also automatically opens
when pressure above 51psi are present.
H. Drain Valve (Current version) : Shown in the “open” position, the
current drain valve model replaced the previous version in 2017.
In addition to a manual drain, the Drain Valve also features an
automatic pressure relief safety that activates when pressures
above 66.25psi are present.
I. Wall Cowl (Not pictured) : A concentric vent located on the sidewall of
the RV, the Wall Cowl is the entry point for fresh combustion air into the
Combustion Air Inlet Tube, and the exit for exhaust air through the
Exhaust Outlet Tube.
J. Gas Shutoff Switch (Not pictured) : The Gas Shutoff Switch, located
above the 12VDC PCB, controls 12VDC power to the Gas Valve. Turning
the Gas Shutoff Switch to the “OFF” position will deenergize the Gas
Valve and result in one of the following fault codes when the Combi goes
to fire: E 112 H, E 121 H, E 122 H, E 202 H, E 211 H, and/or E 212 H.
See “Fault Codes: Further Details”.
K. Warm Water Connection with Aeration Valve : The hot water plumbing
connection to the Warm Water Outlet of the Combi. Elbow fitting consists
of an Aeration Valve with a gravity-fed check valve to ensure that all
2.64gal (10 liter) of water is drained from the Water Container when the
Drain Valve is opened. Must be installed so that hot water plumbing line
flows in a vertical direction (see picture K for proper install). A Combi that
doesn’t completely drain could be evidence of an Aeration Valve issue.
K
Step 1.
Once the Combi receives a call for heat from the CP Plus, a Green LED will illuminate on the PCB. The Combustion Air Motor
and the Circulation Air Fan*will run for 30 seconds to purge the system. The Combustion Air Motor and Circulation Air Fan*
will ramp up to operating level 2 (14,300BTU) fan speeds right before the start of Step 2.
Step 2.
Once the Combustion Air Motor and Circulation Air Fan* has reached operating level 2 speeds, a yellow LED will illuminate on
the PCB. The Magnetic Gas Valve will open at the same time that the Direct Spark Ignitor is energized and begins sparking.
Step 3.
After the three ingredients for combustion (air, fuel, and spark) have been introduced to the Combustion Chamber, the burner
flame will activate. Once the flame presence has been proven by the Flame Sensor, a red LED will illuminate on the PCB.
Heat from the Gas Burner will then make its way into the Water Container and/or be distributed throughout the RV via the duct
work by the Circulation Air Fan*.
*If the Combi is strictly in water heating mode and not furnace mode, the Circulation Air Fan will not operate. The purpose of
the Circulation Air Fan is to operate while the Combi is in furnace mode to distribute hot air throughout the RV via the ducting
system. However, it’ll also act as a cooling device for the Combi in the event of an overheat situation in any operational mode.
Sequence of Operations

CP Plus - Functions
CP Plus –Tips & Tricks

Common Error Codes
#
Flashcode
Error
Error Info
Action
4ssss, slss Current for combustion air motor too high Combustion air motor, cable
harness, or PCB fault Go to Blue Pages: Check Combustion Air
Motor, then PCB
5ssss, slsl Current for combustion air motor too low Combustion air motor, cable
harness, or PCB fault Go to Blue Pages: Check Combustion Air
Motor, then PCB
6ssss, slls Current for combustion air motor too high Combustion air motor, cable
harness, or PCB fault Go to Blue Pages: Check Combustion Air
Motor, then PCB
8ssss, lsss Recheck flash code Electronic fault –Failure in PCB Restart heater, replace
electronics
10 ssss, lsls Plausibility of Combustion Air Sensor Combustion Air Sensor outside
of tolerance range –sensor or
harness
Go to Blue Pages:
Check Combustion Air
Sensor
18 Yellow indicator light flashes (9) times Warm air outlets blocked
circulated air intake blocked Inspect individual outlet apertures, remove air
intake blockage.
20 sssl, slss Plausibility of NTC Water Temperature Sensor Water Temperature Sensor
outside tolerance range –
sensor/harness, excessive temp
Allow system to cool
Go to Blue Pages:
Check WTS
21 sssl, slsl Plausibility of NTC Room Temperature Sensor Room Temperature Sensor
outside tolerance range –
sensor/harness, excessive temp
Allow system to cool
Go to Blue Pages:
Check RTS
22 sssl, slls Plausibility of NTC Air Temperature Sensor
Air Temperature Sensor outside
tolerance range –
sensor/harness, excessive temp
Allow system to cool
Go to Blue Pages:
Check ATS
24 sssl, lsss Current for air circulation motor too high Air circulation motor or PCB
fault Go to Blue Pages: Check Air Circulation
Motor, then PCB
25 sssl, lssl Current for air circulation motor too low Air circulation motor or PCB
fault Go to Blue Pages: Check Air Circulation
Motor, then PCB
26 sssl, lsls Current for air circulation motor too high Air circulation motor or PCB
fault Go to Blue Pages: Check Air Circulation
Motor, then PCB
45 ssls, llsl No 120VAC supply to Combi Fault in 120VAC power supply,
WECO manual reset switch
engaged
Verify 120VAC supply
voltage/engaged GFCI,
reset WECO manual
reset switch
69 slss, slsl Current monitoring for air circulation motor
with CP Plus –software error Air circulation motor, CP Plus (before C01.04.01), or PCB
fault
Go to Blue Pages:
Check Air Circulation
Motor, check CP Plus,
Check PCB
148 lssl, slss Overtemperature of the Combustion Air
Temperature Sensor Combustion Air Sensor outside tolerance range –
sensor/harness, excessive temp
Allow system to cool
Go to Blue Pages:
Check CATS

Common Error Codes
#
Flashcode
Error
Error Info
Action
149 lssl, slsl Overtemperature of the Water Temperature
Switch or Air Temperature Switch Water Temperature Switch or Air Temperature Switch out of
range –sensor/harness,
excessive temperature
Allow system to cool
Go to Blue Pages:
Check WECO, Check
AECO
150 lssl, slls Overtemperature of the Air Temperature
Switch or Water Temperature Switch Air Temperature Switch or Water Temperature Switch out
of range –sensor/harness,
excessive temperature
Allow system to cool
Go to Blue Pages:
Check AECO, Check
WECO
112 slll, ssss Combustion Failure: Flame not detected Flame was not detected during
ignition sequence –potential
combustion issue (air, fuel,
spark)
1)
Check On/Off switch in
ON position 2) Check
supply gas pressure 3)
Check condition of
exhaust and intake -
properly installed, no
damage 4) Ensure
proper grounding and
incoming 12vdc 5) Allow
system to cool and
restart Go to blue
pages: 6) Check ignitor
7) check gas valve 8)
Check PCB
121 slll, lssl Combustion Failure: Flame unstable Flame unstable during
operation –potential
combustion issue (air, fuel,
spark)
Same steps as #112
122 slll,lsls Combustion Failure: Flame not detected Flame was not detected during
ignition sequence –potential
combustion issue (air, fuel,
spark)
Same steps as #112
202 llss, lsls Combustion Failure: Flame not detected Flame was not detected during
ignition sequence –potential
combustion issue (air, fuel,
spark)
Same steps as #112
211 llsl, ssll Combustion Failure: Flame unstable Flame unstable during
operation –potential
combustion issue (air, fuel,
spark)
Same steps as #112
212 llsl, slss Combustion Failure: Flame not detected Flame was not detected during
ignition sequence –potential
combustion issue (air, fuel,
spark)
Same steps as #112
255 CP Plus –Combi communication and/or
12VDC failure Combi 12VDC supply power inadequate or non-existent or
communication failure between
Combi and CP Plus
Verify 12VDC supply
voltage between 11-
15VDC, check CP Plus,
Data Cable, CP Plus 1A
Fuse

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

The Blue Pages: 12VDC
Component Measuring points Function/Setpoint Remark
Ignitor (step 1) Pull out X7 plug
Apply 12 V between X7-11 (+) and
X7-10 or 9 (-)
Ignition spark can be
heard and seen If you cannot hear the ignitor ticking, replace the ignitor
Combustion air motor Pull out X7 plug
Apply 12 V between X7-2 (+) and
X7-5 (-)
Motor runs at full
speed If you cannot hear the motor running, replace the motor
Air Circulation D.C. motor Pull out X3 plug
Apply 12 V between X3-1 (+) and
X3-2 (-)
Motor runs at full
speed If you cannot hear the motor running, replace the motor
Solenoid coil “small”
Pull-in winding Pull out X7 plug
Apply 12 V (< 5 sec.) between
X7-18 (+) and X7-20 (-)
You hear the solenoid
valve opening If you cannot hear the solenoid valve opening, replace the coil
Solenoid coil “large”
Pull-in winding Pull out X7 plug
Apply 12 V (< 5 sec.) between
X7-15 (+) and X7-17 (-)
You hear the solenoid
valve opening If you cannot hear the solenoid valve opening, replace the coil
Component Measuring points Function/Setpoint Remark
Ignitor (step 2) Switch on the furnace
Voltage measurement between
X7-10 or 9 and X7-11
Minimum voltage
10 V If no voltage is measured when the solenoid valve has opened or if it
is less than 10 V:
- detach the plus or minus cable
from the ignitor (ignitor short
circuit input side) or
- replace the electronics
Air Circulation D.C. motor Switch on the furnace (ΔT > 2° C),
voltage measurement between
X3-1 and X3-2
4.5-12 V
(speed is controlled
by LTF)
If the voltage is less than 4.5 V,
replace the electronics
Solenoid coil “small”
Hold-in winding Switch on the furnace (ΔT ≤ 2°C)
voltage measurement between
X7-18 and X7-19
Minimum voltage
10 V After start ramp, consistent voltage If not, replace the electronics
Solenoid coil “large”
Hold-in winding Switch on the furnace (ΔT > 2°C)
voltage measurement between
X7-15 and X7-16
Minimum voltage
10 V After start ramp, consistent voltage If not, replace the electronics
CP Plus digital control panel Voltage measurement on contact pin,
12 VDC supply cable Minimum voltage 8 VDC If voltage present, replace control panel. If no voltage measured,
replace electronics
Voltage: Applied
Voltage: Measured

12VDC PCB
•F1: Input fuse 10 AT
•12V: Contact pins, supply cable
•X3: D.C. motor connector
•X4: FrostControl connector (Euro only)
•X5: Control panel connector
•X6: Diagnostics device connector
•X7: Cable harness connector, 12VDC
•X8/X9: Contact pins, cable bridge
•X10/X11: Contact pins, room temperature sensor
•X16: Cable harness connector, 12VDC/120VAC
(Connection for 120VAC electronics)
•X18: Water system sensor connector
•X19: Air system sensor connector
X10/X11
X8/X9
X4 F1 X5
12V X6
X3 X16 X19
X18
X7

The Blue Pages: 120VAC
Component Measuring points Function/Setpoint Remark
Input fuse F4 Continuity test on
removed fuse Continuity (0 Ω) If no continuity, replace fuse
Component Measuring points Function/Setpoint Remark
120 V supply cable L3 Voltage measurement between
N and L 120 V voltage If no voltage is measured, check supply cable
Cable harness connector
Temperature limiter X4
(Left side)
Voltage measurement between
N and L 120 V voltage If no voltage is measured, check fuse
Cable harness connector
Temperature limiter X4
(Right side)
Voltage measurement between
N and L 120 V voltage If no voltage is measured, check temperature limiter
Cable harness, heating
elements X2 Voltage measurement X2-1 and X2-3 120 V voltage or 60 V voltage (depending on
power setting)
If no voltage is measured,
check power electronics
Cable harness, heating
elements X2 Voltage measurement X2-2 and X2-4 120 V voltage or 60 V voltage (depending on
power setting)
If no voltage is measured,
check power electronics
Continuity
Voltage: Measured
F4
X2
X1
S
•X1: Cable harness connector 12VDC/120VAC
(Connection to 12VDC electronics)
•X2: Cable Harness connector, heating elements
•L3: Connector for 120VAC supply cable
•F4: Input fuse, 10AT
•S: Safety circuit connector
L3

Fault Codes: Further Details
W 45 H
The W 45 H warning code signifies a disruption in 120VAC to the
120VAC PCB on Combi Plus models.
More times than not, the cause of the W 45 H code is a loss of
120VAC supply power to the Combi. This could be the result of a failed
20A fuse at the breaker panel or the fact that the NEMA 5-20P plug
from the Combi simply is not plugged into the outlet. A tripped GFCI
outlet, if the manufacturer has elected to use one, could also cause
this issue.
If the Water Temperature Switch (WECO) senses temperature above
185°F (85°C), the manual resettable switch (See Yellow Circle) will
activate and issue a W 45 H error code. If this occurs, simply power
OFF the Combi and insert a pen or thermostat screwdriver into the
access hole on the left side of the PCB cover (See Red Circle). Feeling
and hearing a *click* is evidence of a WECO that has been reset.
W 255 H
The W 255 H warning code signifies a loss of 12VDC supply
voltage to the Combi and/or a communication loss between the
Combi and the CP Plus.
Although the CP Plus and Combi are both powered by 12VDC,
they are powered separately and do not share the same 12VDC
circuit. Communication between the CP Plus and Combi is
accomplished through a 6 pin Data Cable, where the color of the
wires on each plug match.
A W 255 H warning code will occur when the CP Plus loses
contact with the Combi. This could occur due to a disruption in
the 12VDC power supply to the Combi (must be between 11-
15VDC) or a damaged/disconnected Data Cable between the
CP Plus and Combi.
DATA CABLE
12VDC
CONNECTION
WECO
ACCESS HOLE
CABLE
CONNECTION CABLE CONNECTION
E 112 H, E 121 H, E 122 H, E 202 H, E 211 H,
and/or E 212 H
All (6) of these error codes refer to either a “Flame Unstable” or “Flame
Not Detected” malfunction, which essentially means that there was a
problem with at least one of the three ingredients for combustion (air,
fuel, spark). The three main reasons are detailed below.
The Gas Shutoff Switch is an ON/OFF switch that is wired in series
between the 12VDC PCB and the Gas Valve. If it is in the OFF
position, the Gas Valve will NOT open during the ignition sequence to
allow gas into the combustion chamber.
The Combi utilizes a “pipe within a pipe” Exhaust/Fresh Air Intake
system to keep the two separate while ensuring a balanced level of
combustion. If the interior Exhaust Pipe develops a hole or becomes
disconnected, the Exhaust and Intake Air will mix, leading to improper
combustion and one of these error codes.
The Combi requires a dynamic supply pressure of 11-13”WC. If the
gas supply is outside of this range, or not ON at all, during start up or
operation the Combi will issue one of these error codes.
GAS SHUTOFF
FRESH AIR
EXHAUST AIR

Step 3: The Fan Wheel must be separated from the Circulation Air Fan Motor Shaft by loosening the 2mm threaded bolt which is
tightened to the flat portion of the Motor Shaft. Once reassembled, the end of the Fan Wheel should be flush with the end of the
Motor Shaft so that it spins freely without rubbing on the housing before being secured by the 2mm threaded bolt.
Access Instructions
If access to components such as the Circulation Air Fan must be
achieved after proper troubleshooting:
Step 1: Remove (4) labeled T20 Torx screws and remove Combi End
Cover.
A) –Access to the Combustion Air Fan can be achieved by lifting off
cover plate labeled “A”. Combustion Air Fan is secured into place with
(3) T20 Torx screws. Replacement Combustion Air Fan is one entire
assembly and comes with new O-ring.
A
Step 2: Remove Fan Wheel Cover by removing (4) labeled T20 Torx
screws.
1
2
3
Step 4: Remove the PCB Cover by removing the (2) labeled T20 Torx
screws. The Cover can then be removed by freeing the (2) clips at the
bottom of the Cover by pulling down and away.
5
Step 5: The Circulation Air Fan Motor can now
be removed from the housing by disconnecting
the wiring harness to the PCB and removing
the (2) labeled Phillips head screws.
Replacement screws come with replacement
Circulation Air Fan Motor.
4

CLOSED
Winterization
The Combi furnace does not feature a frost protection function. The water container must be drained if the RV will not be used
whenever there is a risk of frost as severe damage to the plumbing components and the Combi could occur due to freezing.
Damage caused by freezing or an unsuitable winterizing fluid is not covered by warranty.
To make sure that all the water drains properly from the water container, place a big enough vessel underneath the drainage
socket of the pressure relief/drain valve (>2.64 gallons/10 liters).
1. Use the main switch or pump switch to switch OFF the power to the water pump assembly.
2. Turn OFF or disconnect the city water connection, if present.
3. OPEN all water release points, e.g. cold and hot water faucets, etc.
4. OPEN the drain valve by moving the lever to position C (see illustration).
5. Leave the drain valve OPEN while the Combi is winterized.
Once all the water is removed, the Combi is winterized.
A Combi that does not completely drain could be evidence of an issue
with the Warm Water Connection/Aeration Valve. Current Drain
(since 2017)
Previous Drain
(until 2017)
e
f
g
Winterizing the RV with Winterizing Fluid
Winterizing the RV with a winterizing fluid is only possible with an installed bypass kit
(see example illustration), which is not in the scope of supply, refer to the RV
manual.
1. Drain the water container (as detailed in Winterization instructions above).
2. Turn the valves of the bypass kit according to the supplier’s or RV
manufacturer’s guidelines.
3. Flush the water system with a suitable winterizing fluid according to the
supplier’s or RV manufacturer’s guidelines.
Bypass Kit Example
NOTE: The illustration to the right is an example of a bypass kit. Bypass kits
are not included with Truma systems and is therefore the decision of the
installer as to whether a bypass kit is installed in the RV’s plumbing system,
as well as how it is designed and configured. Always refer to supplier’s or RV
manufacturer’s guidelines to determine proper operation of bypass kit.
To isolate the Truma Combi from the RV plumbing system via Bypass Kit Example
once drained:
e. CLOSE cold water inlet valve by turning valve perpendicular to piping direction.
f. CLOSE hot water outlet valve by turning valve perpendicular to piping direction.
g. Turn bypass valve to OPEN position.
Drain Valve
Bypass Kit Example
OPEN

Combi Test Procedure
Purpose:
The purpose of this procedure is ensure that the Truma Combi, after being installed in accordance with the applicable
manuals and standards, is functionally tested prior to delivery. This test procedure is not meant to test all functions of the
system, and does not absolve the manufacturer or service technician from their responsibilities relative to the manuals
delivered by Truma Gerätetechnik GmbH & Co. KG.
Synchronized Not
Synchronized
❑Ensure that the Gas Shut Off Switch on the top of the Combi is set to
the “ON” position.
❑Ensure that the gas supply and 110VAC (if available) are both
connected and turned on.
❑If there is a switch for the 12VDC supply to the Truma Combi, make
sure it is turned on.
❑Select the “Heating Mode” on the CP Plus control panel and turn the knob to
the desired heating setting to 86⁰F (30⁰C) to ensure that there is a demand
for heat.
❑Note that if the internal temperatures in the vehicle are above 86⁰F (30⁰C) the
Combi will not see a demand for heating and the heating test cannot be
carried out.
❑Select the Power Source as “GAS”.
❑Run the Combi in this setting for a minimum of 5 minutes and check to see if
the flame icon is flashing, indicating that the system is running.
❑Change the Power Source from “GAS” to “EL1” (Electric 1) setting “d” and
check that the flame icon is still flashing.
❑Change the Power Source from “EL 1” to “EL 2” (Electric 2) setting “e” and
check that the flame icon is still flashing.
❑At this point, check that warm air is coming out of all Warm Air Outlets.
❑Select Water Heating Mode “BOOST” (d) on the CP Plus and wait to see that the
symbol starts to flashing, indicating that there is a demand for water heating.
❑The function test is now complete. Turn off the water supply, LPG, and 110VAC.
❑Ensure that the Gas Shut Off Switch remains in the “ON” position.
❑Open the Drain Valve (to the “c” position) to drain water from the system.
❑A failure to drain the system could result in frost damage, which is not covered
under the scope of Truma’s Manufacturer Limited Warranty.
❑Ensure that the Drain Valve is closed (in either the “a” or
“b” position).
❑Fill the system with water.
❑Check that the CP Plus control panel is synchronized
with the system.
❑If the CP Plus is not synchronized, enter the
“Settings” option denoted by the wrench symbol and
select the “RESET” option and then select “PR
RESET”.

Spare Parts & Accessories

Spare Parts & Accessories
Pos. no. Part number Description Information
10 34020-00059 Cover incl. grill
20 34020-06500 Truma Combi connection cover
30 34020-00058 PCB Truma Combi comfort/comfort plus
30 34020-00057 PCB Truma Combi eco/eco plus
40 34020-00060 Power PCB, 120V with cable
50 34020-00078 Combustion Air Motor with round cord seal, screws
60 34000-04700 Fan Wheel –air incl. threaded bolt
70 34020-61300 Air Circulation Motor DC
110 47000-00056 Truma CP plus US
120 34030-28500 CP plus mounting frame
130 34030-28600 Truma CP plus control knob
140 10010-41900 CS screw TP 3x6-A2K-H1
150 36110-03 Control panel cable, 29.5ft (9m)
160 34030-28700 Connecting cable CP plus
170 50020-27800 Fuse holder with fuse 1A
180 34020-00263 Room Temperature Sensor
190 34000-71900 Cable for Room Temperature Sensor, 13.1ft (4m)
200 34030-35600 CP plus cover
210 34020-00178 Elbow fitting with Aeration Valve for rigid piping Ø 12mm
220 34000-17700 Condensation tube 3ft (0.9m) long
230 34020-00177 Elbow fitting for rigid piping Ø 12mm
240 70143-18 Pressure Relief Valve kit US
250 36503-01 Water Pressure Regulator
260 34030-72600 Adapter Ø 12mm to 1/2in. CTS kit
270 36230-04 Wall cowl kit CW black 3.3ft (1m) long
270 36230-02 Wall cowl kit CW pure white 3.3ft (1m) long
280 34020-00181 Cowl outer part black
280 34020-00180 Cowl outer part pure white
280 34020-00638 Cowl outer part anthracite (dark gray)
290 34020-00088 Screw / Nut set
300 34000-10700 Seal set
310 34020-14200 Exhaust duct clip
320 39010-61800 Hose clip 70-90
330 39590-00 Clamp ZRS, Ø 80mm
340 34091-02 Elbow BGC
350 34310-02 Blank cover VD-Combi to close one of the lower warm
air outlets of the eco (plus)
Y34030-25600 Seal set not illustrated