Aqua Hot runs 30 seconds then shut down

[IASM]

Aqua Hot 650D
When burner switch is turned on green light comes on.Unit fires and runs clean. After 30 seconds or so green light dims and burner shuts down and green light goes out. If i turn off then back on the cycle repeats.This happend a few years ago on a long distance trip and would do this cycle thing when we got parked but would start working ok later in the evening.
Last week i decided to try to get to the bottom of it so replaced filter,nozzel,set electrodes and still the 30 second run.I also used a fuel can to confirm fuel.

I bridged the thermostat and replaced the flame sensor with same results.
I have to think the green burner light dimming and going out is a clue.
Any thoughts? It seems if its running it would stay running unless something tells it to stop?

[IASM]

Just to close the thread in the event someone else has the same problem. After testing the circuits for voltage and testing the flame sensor the only thing left was the controller. $800.00 for the new solid state unit and it works fine now.

[shootist]

Thanks for the update, that's a tough one to bite the bullet on with nothing to go on experience wise.

[IASM]

They provided a very good flow chart for testing. Every component can be tested so in the end all test pointed to the controller. This would have been a lot faster had i had the flow chart when i started.I think this test material will apply to most of there burners so worth keeping on file if one has an aqua hot.