Aqua Hot not firing up

[06Windsor]

Good afternoon group. I am having issues with my Aqua Hot AHE-100-04S not firing up. What I have done is a serviced it which includes a new filter and a new orfice. After putting it back together it worked great. A day later flipped the diesel switch on and after a few seconds the light goes out and it wont fire up. So I go back out and remove the burner again cause I read that there might be trash in the screen on the fuel pump inlet. so I tear it down cleaned what little trash I found and cleaned all the wiring connection and the flame eye. adjust the electrodes. Put it all back together and it fired up and lasted 4 days and the light went out and quit firing up again so I shut it off and ill try it again later today. has anyone had this problem and any luck with a repair to fix it. is this a common problem with these ? I don't think its a thermostat issue cause it will fire up. The electric side works fine. I just the diesel side to keep up with the cold weather we are having. Any ideals would be appreciated. Seems to be a intermediate issue. Was working perfectly up to about 3 weeks ago and all this started. 

[vito.a]

Over the years I've spent a great deal of time troubleshooting our Aqua Hot system.  

It could be the electronic controller board, the ignition coil, or the flame sensor.  

You really need to follow the troubleshooting flow chart in the Aqua Hot manual or you're just guessing.  

But if I had to guess, I'd say your flame sensor is going because you had it working each time you took it apart and cleaned it.  Flame sensors are relatively cheap and you can easily install it. 

I'd start out by checking the flame sensor resistance with and without light.  

If the flame sensor is operating properly, the ohm-meter should register high resistance, over 100K Ω when the glass surface is covered, and less than 200 Ω when exposed to a light source.

Best of luck!

[hex_nut]

I had the same type of issues.  Following the troubleshooting chart is very important.  In my case, I got to the part of testing the ignition coil and found my problem.  A week coil will not consistently provide ignition.  First I replaced the old coil ignition wires, no joy.  So, I replaced the coil ($$$$).  It has worked flawlessly ever since.

[Chargerman]

     Agree strongly with the above from both guys stating to follow the troubleshooting guide. It is VERY good. You can get it on the Aquahot site. In the document section you can get all of the manuals. 
    Vito, I thought flame sensors were either good or bad? Is it true that they can be occasionally bad?

[Jetjockey]

What indications does the control board show. Is the system calling for heat and is the board sending a call to light the burner?