thermo top - runs but cuts out.

[mattnj]

I have been messing about with a thermotop from a rover 75....for £30 and after a load of fiddling about i have it running.

Fan runs for say 10secs. Then stops.
Pump starts ticking, fan runs slowly and cranks up. Burner lights immediatley and burns well, no smoke, lots of heat.

It cranks up to full power over say a minute and it seems like as soon as it hits full power it cut outs.

Fan stops for a few secs then starts and there is a load of white smoke that comes out.

I am assuming there is a flame/temp sensor that thinks its not alight?
I see there is an NTC sensor on the pcb, Can anyone confirm what causes this behavoir?

 

[David2452]

It may be that you are running it on a test bed with a tank which quite quickly gets up to temperature, in that case the behaviour sounds like it is running normally and then going through its shut down process which can cause a bit of smoke, the glow pin is re energized during shut down to burn off residual diesel in the chamber. If you are running it on the boat with a decent loading (5.5kw or more) it may simply need some air purging from it. Remove the hose from the output when cold as soon as you have hit the start button to purge air from the exchanger. If you have fiddled with the PCB it is also possible that the sensor pressure and positioning has been disturbed, Webasto refuse to sell PCBs any more due to this in the past and now only supply them installed on a heat exchanger. The flame sensor is combined with the glow pin and the mechanism for shutting down on a flame out is the resistance of the glow pin/flame sensor drops below 0.6 Ω.

 

[mattnj]

It may be that you are running it on a test bed with a tank which quite quickly gets up to temperature, in that case the behaviour sounds like it is running normally and then going through its shut down process which can cause a bit of smoke, the glow pin is re energized during shut down to burn off residual diesel in the chamber. If you are running it on the boat with a decent loading (5.5kw or more) it may simply need some air purging from it. Remove the hose from the output when cold as soon as you have hit the start button to purge air from the exchanger. If you have fiddled with the PCB it is also possible that the sensor pressure and positioning has been disturbed, Webasto refuse to sell PCBs any more due to this in the past and now only supply them installed on a heat exchanger. The flame sensor is combined with the glow pin and the mechanism for shutting down on a flame out is the resistance of the glow pin/flame sensor drops below 0.6 Ω.

Thanks for the reply!
I sorted it, after a load of internet searching, I ended up concluding the PCB was dodgy last night, there is an internet article on how 3 of the surface mount resistors burn out as they are covered in while glue (to hold capacitors in place)

So, I was feeling brave, tested them with a meter in situ, then and unsoldered them (very tiny these surface mount resistors) and then re-soldered some standard resistors and bingo, it works perfectly!

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