Did you confirm that the unit is displaying the correct room temperature?

Just to clarify, the LED display on the unit's front panel does not display the room temperature but the desired temperature you want. When you power the unit on the LED display defaults to 25°C which is too high for us so we use the +/- on the remote to reduce this to 20°C.
To know what the actual room temperature is we use have a digital thermometer that we bought separately.

As Dodgydave suggests, measure the voltage across the relay coil when the heater is supposed to be on and when it is supposed to be off.

Unfortunately I'm back at work, so won't be able to do check this now until the weekend.

When you say the heating is not turning off, what exactly is giving you the idea that it is not turning off?

Because our external digital thermometer is showing the room temperature reaching 23-24-25°C (which is uncomfortable for us) even when we have set the desired temperature on the unit to the lowest setting 15°C right from the off set!
I also bought an electricity usage monitor which shows electricity being continuously used at the chosen Heat setting ie 1kwh at Low heat setting, 1.5kwh at Med heat setting and 2.5kwh at high heat setting.

I ask because a lot of heaters use a PID controller

I really don't believe this unit has a PID temperature controller... it was about £80 when knew and I would imagine any that have one of these PID's would be a way more expensive... I still think it's faulty.

 

new not knew!! (typo)

 

Just to clarify, the LED display on the unit's front panel does not display the room temperature but the desired temperature you want. When you power the unit on the LED display defaults to 25°C which is too high for us so we use the +/- on the remote to reduce this to 20°C.
To know what the actual room temperature is we use have a digital thermometer that we bought separately.

My question is: Does the unit have a feature whereby it can show the room temperature?
Or, is there a User Manual?

In other words, we are back to square one: We need to check if the temperature sensor is working.

 

Sorry one other quick question, where does one

My question is: Does the unit have a feature whereby it can show the room temperature?

no I'm afraid it doesn't.

Or, is there a User Manual?

Yes, there is a User manual (see attached PDF)

 

Have you checked that neither the On nor the Off timer is active?

 

We've never used the Timer feature on this unit, so the On timer and Off Timer for switching the unit on and off has never been set. Also you would know if they had been set as the Timer LED on the front Display panel would be on.

 

When I get round to testing the relays later this week, if they check out fine (which I think they probably will) then I may just give up and go buy another oil radiator. Keeping this one as a spare, as at least it does warm up the lounge pretty quickly and we can just turn it off as and when we need to using the remote.

 

In that case, you could add wire links across the relay contacts so the heater will be on from power up and use an external thermostat.

 

use an external thermostat.

I wonder how the heater would respond? The user manual (in the link above) mysteriously states "Never use the plug as a switch to start and turn off the heater. Use the provided power button located on the control panel." It also states "Do not use an external timer."
I can't think of any justification for those strange instructions (except, perhaps, that the heater's MCU doesn't reboot correctly and gets confused).
Edit: Come to think of it, there would be justification if the heater's own timers were in use.

 

I wonder how the heater would respond? The user manual (in the link above) mysteriously states "Never use the plug as a switch to start and turn off the heater. Use the provided power button located on the control panel." It also states "Do not use an external timer."
I can't think of any justification for those strange instructions (except, perhaps, that the heater's MCU doesn't reboot correctly and gets confused).
Edit: Come to think of it, there would be justification if the heater's own timers were in use.

I've tested this... if you use the power button on the control panel (or on the remote) the LED Display shows a desired temp of 25°C and Heat Level "High" (ie these are the default settings when powered on). However, if while the unit is running you switch it off and on at the plug , the unit powers into Standby mode (so basically it's off) and you then have to press the power button on the panel or on the remote. I don't really like this but don't know how to get round it. Maybe it's the firmware on the pcb board processor that controls this, along with the switching of the relays on and off when the resistance on the thermistor changes.

Anyway, got home early today and tested both relays and as expected they're working fine. Resistance is around 425ohm across the coil, did a continuity test and the relays are not "welded", applied 12v across the coil of each relay I can here the latch clicking... so all good.

Not going to try anything else, was hoping it would be simple to fix. Going to put it all back together again so we can start using the heater (with the remote) and will look to buy another that does switch off and on when it goes above or below the set desired temperature.

Thanks again to all for your help with this problem