Ideal RD2 450 - Thermistor

[Schmill]

Not to throw a spanner in the works but i regularly go on jv's with BG lads to these

BG lads 'we've fitted several harness, several boards' and yet the damn led3 lockout keeps coming back

Right have you checked the resistance of the plate ignitor? Anything more than 90 ohms boiler logic thinks its not lit and led will come on

So matey id just have a check of this before you fire a harness in.. Glow plug is a lot cheaper than a harness

Cheers, I think I'll stick a harness in anyway, (as I was getting intermittent strange readings from the flow sensor, and I've ordered it already!), but I'll also check the plate ignitor. I'm fairly sure that it's the harness though, (at least partiallly), as sometimes the boiler doesn't even get to the point of attempting to light before it aborts the startup process and the LED flashes.

I'll let you know how it pans out

 

[nashd1]

Schmill
just to let you know I had exactly the same fault and it was the red thermistor breaking down when 5v from PCB is applied - normally you'd expect 10k at 25C from a NTC thermistor. The blue one is the same except colour but as you say you have ordered the harness it's best to replace the whole lot.
Took a while to fault diagnose though because i had no idea about the reliability of these sensors. While i was waiting for the harness i fitted a 4.7k resistor in place on the pcb connector with the old harness in place to confirm. The boiler worked fine, obviously with less effiecency i would imagine...
nash

 

[Agile]

Its not with "less efficiency" !

Its without controlling the heat output !

Thats potentially dangerous!

Tony

 

[nashd1]

Its not with "less efficiency" !

Its without controlling the heat output !

Thats potentially dangerous!

Tony

Hi Tony
Just saw your comment as I didn't get an email notification. Please explain how this is not controlling the temperature? I have experience in electronics in a professional capacity, perhaps you know that the ntc thermistor curve at 60 deg c for this type is around 4 to 5k ohms. Therefore the control is the resistance set. Granted it does not provide the full gas modulation you would get from a thermistor so in this case it will take longer to reach the desired temperature.
I am not recommending it as a permanent solution. But to state this is dangerous is a little strong. Perhaps I am missing something and you can elaborate.
N