Burner Problems

I am having issues with my 8gpm 12v Largo hot box. It will fire up and have hot water for a short time then run cold. It will fire back up but you never know when. I only have a couple hundred hours on this unit. I looked at the springs and electrodes (?) and they looked pretty clean. At least the metal part was clean. The white part was covered in black soot I presume. Kind of hard to do any truck washing in this weather without consistent heat. What should I be looking at to fix this.

Themostate i bet mine would do that it ate themostate like candy

How is your fuel filter?

Filter looks like it is getting plenty of fuel through. I am going to buy a new one anyway and I just ordered a new thermostat. Hopefully that gets me back up and running.

Also check the flow switch to be sure it works but sounds like the low switch or the thermostat - had both go within a year at different times but once replaced life has been good...