Dimplex Duoheat diagnostics

I don’t know much about these heaters but maybe this video might help:

Best Usage Dimplex Duo Heat Night Storage Heater controls

Hey ​@Dave-Nice-VIII,

I’ll tag ​@Firedog as he’s great at helping with storage heaters. I also managed to find a troubleshooting guide that i’ll post below for you to look through.

1. Check for Control Locks (Most Common)

If the buttons are unresponsive or the background setting cannot be changed, the heater might be locked by a central timer (e.g., RXPW4) or in Child Lock mode. 

• Central Timer Lock: If you have a separate central programmer, ensure it is set to the SUN (constant) position, not "Setback" (moon symbol) or "Off". A green light on the heater's lock icon indicates a central timer is overriding the controls.!--tgqphd|[]-->!--tgqphd|[]-->
• Child Lock: If a red LED is lit next to the lock icon, press and hold the +and - buttons together for 2 seconds to unlock.

2. Verify Background Mode Setting 

Ensure the background heat is actually programmed to run.

1. Press the +button until all red bars are illuminated.
2. Press and hold the + button until all lights disappear except for one flashing red bar.
3. Adjust this flashing bar to a higher setting (e.g., 4th-7th bar) using the + and - buttons.
4. Wait a few seconds for it to return to normal operation. 

3. Check Off-Peak Power Supply 

The storage core only charges during off-peak hours (e.g., Economy 7). 

• Check that the off-peak supply is active.
• Check if the heater works on "boost" (daytime) mode. If it works on boost but not overnight, the issue is with the off-peak supply or the internal overnight charging mechanism.
• Note: Ensure the wall switch for the storage supply is left on. 

4. Reset the Heater 

If the lights are flashing, the controls are unresponsive, or there was a power failure, a reset may be needed. 

• Power Reset: Switch the heater off at the wall socket (both peak and off-peak switches) for at least 10–30 minutes, then turn it back on.
• Diagnostic Exit: If the display is flashing, it might be in diagnostic mode. Press and hold the - button for 10 seconds (or until the blue light goes off) to exit.

5. Check for Component Faults

If the above steps do not work, it could be a hardware failure:

• Failed Components: The internal thermostat or control board may be broken.
• Blown Fusible Links: These can fail, preventing the background heater from charging.
• Sensor Faults: The 1st or 2nd red LED flashing can indicate room or core sensor faults. 

Howdy ​@Dave-Nice-VIII !

Firstly, welcome to the OVO Forum! The name’s Blastoise186 and I’m one of the forum volunteers around here. :)

It’s nice to have a unique puzzle too - this actually took me a while to research and figure out, so you have my thanks for that. :D

As far as I can tell after checking with Dimplex, if the thermal cut-out has tripped, you can’t reset it on your own, you’ll need to either ask the installer, Dimplex Customer Service or an electrician to reset it. I managed to get the circuit diagram for the Dimplex DuoHeat Duo300i which also applies to the Duo400i and Duo500i and by the looks of things, the thermal cut-outs are buried pretty deep inside the unit so you probably won’t be getting to them yourself without disassembling the entire radiator, which only an electrician should do. These usually only trip in the event of an overheat, so you may want to get the entire unit checked over anyway.

My thoughts are that the meter itself is likely fine, especially as the other unit works correctly - thermal cut-out is the most likely culprit I can think of.

Hope this helps!