Question 1

Error W 301 H, W 417 H, E 540 H: Overvoltage > 16.4 V

Accepted Answer

Possible cause: Battery voltage or voltage sources too high. Check the battery voltage and whatever's supplying it, such as the charger.

Question 2

Error W 302 H, W 418 H, E 541 H: Low voltage - battery voltage has dropped below 10.0V

Accepted Answer

Possible cause: Battery voltage has dropped below operating threshold. Charge the battery, fitting a new one if it's old/required.

Question 3

Error W 303 H, W 411 H: Low voltage risk - battery voltage has dropped below 10.8V

Accepted Answer

Possible cause: Battery voltage approaching low threshold. Charge battery.

Question 4

Error E 560 H: The heater's hit its maximum number of start attempts and is locked out

Accepted Answer

Possible cause: Exceeded allowed failed startup cycles, triggering operation lockout. Contact an authorised service agent.

Question 5

Error E 561 H: The heater won't start - it's locked out after five failed start attempts

Accepted Answer

Possible cause: Failure to ignite after five attempts, leading to lockout. Check the fuel supply reaching the appliance.

Question 6

Error E 565 H: The heater won't start; the flame keeps failing to be detected

Accepted Answer

Possible cause: Flame failure or lack of fuel detection during operation. Check the fuel supply reaching the appliance.

Question 7

The water's taking a really long time to heat up

Accepted Answer

Possible cause: Water container furred. Descale water system

Question 8

Water's running straight back out - the water container won't fill

Accepted Answer

Possible cause: Safety / drain valve open. Close safety / drain valve

Question 9

The water container won't drain, even with the safety/drain valve open

Accepted Answer

Possible cause: The safety/drain valve's drainage socket is blocked. Look for dirt, slush, ice, leaves or the like in the opening and clear it if needed

Question 10

The water container won't drain, even with the safety/drain valve open

Accepted Answer

Possible cause: Water pipe frozen. Thaw water pipe

Question 11

Water's dripping or flowing from the safety/drain valve's drainage socket

Accepted Answer

Possible cause: Water pressure too high. Check the pump pressure doesn't exceed 2.8 bar. Fit a pressure reducer if it's hooked up to mains water, to stop the water container seeing higher pressures than that.

Question 12

The FrostControl opens after the heater's been switched off

Accepted Answer

Possible cause: Below roughly 3°C, the FrostControl opens on its own. Switch the heater on - with it off, the FrostControl won't close again until the temperature climbs to around 7°C or above, unless a FrostControl heating element is fitted.

Question 13

The FrostControl won't close any more

Accepted Answer

Possible cause: The FrostControl's own temperature has dropped below roughly 7°C. Switch the heater on - with it off, the FrostControl won't close again until the temperature climbs to around 7°C or above, unless a FrostControl heating element is fitted.

Question 14

The FrostControl won't close any more

Accepted Answer

Possible cause: The rotary switch isn't set to 'Operation'. Turn the FrostControl's rotary switch to 'Operation', then press the pushbutton in until it clicks.

Question 15

The FrostControl won't close any more

Accepted Answer

Possible cause: FrostControl faulty. Must be replaced by an authorized service agent

Question 16

After the appliance starts, thick smoke keeps coming out of the wall cowl for over a minute

Accepted Answer

Possible cause: Could be a fuel supply fault, incorrect installation, or a restricted combustion air inlet. Stop using the appliance immediately due to fire hazard and contact customer service

Question 17

In Diesel mode, the heater shows a malfunction after the 230V mains supply is interrupted

Accepted Answer

Possible cause: A break in the external 230V mains supply while the heater is running in Diesel mode.. Switch the heater off and back on at the control panel to clear the malfunction. If the mains interruption is likely to last longer, switch the heater over to Electro mode instead.

Question 18

The heater flags a combustion problem

Accepted Answer

Possible cause: An issue during the combustion process, such as the fuel supply running low.. In Gas mode, the heater automatically switches over to Electro mode - once the underlying cause is fixed, switch the heater off and back on at the control panel to restore normal mixed-mode operation. In Diesel mode, switch the heater off and back on, or switch over to Electro mode if the interruption is expected to last longer.

Truma Combi D

Technical Specifications

Master Troubleshooting & Diagnostics Matrix

Also Fitted In

Error Code / Indicator	Symptom / Meaning	Possible Cause	Step-by-Step DIY Fix	Suggested Actions
`W 301 H, W 417 H, E 540 H`	Overvoltage > 16.4 V	Battery voltage or voltage sources too high	Check the battery voltage and whatever's supplying it, such as the charger.	DIY Safe
`W 302 H, W 418 H, E 541 H`	Low voltage - battery voltage has dropped below 10.0V	Battery voltage has dropped below operating threshold	Charge the battery, fitting a new one if it's old/required.	DIY Safe
`W 303 H, W 411 H`	Low voltage risk - battery voltage has dropped below 10.8V	Battery voltage approaching low threshold	Charge battery.	DIY Safe
`E 560 H`	The heater's hit its maximum number of start attempts and is locked out	Exceeded allowed failed startup cycles, triggering operation lockout	Contact an authorised service agent.	Professional Intervention Required
`E 561 H`	The heater won't start - it's locked out after five failed start attempts	Failure to ignite after five attempts, leading to lockout	Check the fuel supply reaching the appliance.	DIY Safe
`E 565 H`	The heater won't start; the flame keeps failing to be detected	Flame failure or lack of fuel detection during operation	Check the fuel supply reaching the appliance.	DIY Safe
`N/A`	The water's taking a really long time to heat up	Water container furred	Descale water system	DIY Safe
`N/A`	Water's running straight back out - the water container won't fill	Safety / drain valve open	Close safety / drain valve	DIY Safe
`N/A`	The water container won't drain, even with the safety/drain valve open	The safety/drain valve's drainage socket is blocked	Look for dirt, slush, ice, leaves or the like in the opening and clear it if needed	DIY Safe
`N/A`	The water container won't drain, even with the safety/drain valve open	Water pipe frozen	Thaw water pipe	DIY Safe
`N/A`	Water's dripping or flowing from the safety/drain valve's drainage socket	Water pressure too high	Check the pump pressure doesn't exceed 2.8 bar. Fit a pressure reducer if it's hooked up to mains water, to stop the water container seeing higher pressures than that.	DIY Safe
`N/A`	The FrostControl opens after the heater's been switched off	Below roughly 3°C, the FrostControl opens on its own	Switch the heater on - with it off, the FrostControl won't close again until the temperature climbs to around 7°C or above, unless a FrostControl heating element is fitted.	DIY Safe
`N/A`	The FrostControl won't close any more	The FrostControl's own temperature has dropped below roughly 7°C	Switch the heater on - with it off, the FrostControl won't close again until the temperature climbs to around 7°C or above, unless a FrostControl heating element is fitted.	DIY Safe
`N/A`	The FrostControl won't close any more	The rotary switch isn't set to 'Operation'	Turn the FrostControl's rotary switch to 'Operation', then press the pushbutton in until it clicks.	DIY Safe
`N/A`	The FrostControl won't close any more	FrostControl faulty	Must be replaced by an authorized service agent	Professional Intervention Required
`N/A`	After the appliance starts, thick smoke keeps coming out of the wall cowl for over a minute	Could be a fuel supply fault, incorrect installation, or a restricted combustion air inlet	Stop using the appliance immediately due to fire hazard and contact customer service	Professional Intervention Required
`N/A`	In Diesel mode, the heater shows a malfunction after the 230V mains supply is interrupted	A break in the external 230V mains supply while the heater is running in Diesel mode.	Switch the heater off and back on at the control panel to clear the malfunction. If the mains interruption is likely to last longer, switch the heater over to Electro mode instead.	DIY Safe
`N/A`	The heater flags a combustion problem	An issue during the combustion process, such as the fuel supply running low.	In Gas mode, the heater automatically switches over to Electro mode - once the underlying cause is fixed, switch the heater off and back on at the control panel to restore normal mixed-mode operation. In Diesel mode, switch the heater off and back on, or switch over to Electro mode if the interruption is expected to last longer.	DIY Safe