Aquahot burner switch light goes out

[Vfaozzy]

Fairly new to posting here but wanted to let everyone know about the Aquahot 450-DE4 troubleshoting I went through over the last 3 days and hopefully prevent some headaches.

Scenario: Burner switch light in coach would go out after several hours, randomly, mostly at night with no hot water or heat being used. Showering with water getting cold would be first indication of issue. After researching the issue I was advised that it was electrical or fuel related so...

Steps to rectify problem: Serviced unit at service center, same problem. Systematically and methodically replaced fuel filter, cleaned and tested flame sensor, checked high and low temperature thermostats, swapped burner switch with electrical heater switch inside coach, tested interlock switch, checked and hot wired control thermostat, jumped diesel burner switch at electrical control panel, replaced electrical control panel (have a spare),...scratch my head and say choice words, nothing.

During the course of the troubleshooting I removed and reinstalled the burner 4 times, which is fairly simple in a Cornerstone. Nothing was working...more head scratching. This was very time consuming as I was required to restart the heating process, wait for the temp to stabilize and then wait to see if the switch light would stay lit! It, at times took hours.

NOTHING WORKED! Can’t be electrical as I just checked pretty much everything so maybe it’s a fuel problem.

Diesel tank full, new filter, serviced, new nozzle and burner disk. Remove burner again and blow out fuel lines, check fuel strainer screen at fuel supply line...it is dirty! Reassemble and turn on...nothing! Now it will not even light off and the switch light goes out after 30 seconds...I made the problem worse! Head scratching anain. I do not have a fuel pressure tester so I guess I will take it in or shoot some holes in it!

Next day, thinking, I jumped the temperature sensor at one point during the troubleshooting and the fluid temperature got extremely hot...did that trip the DC high temperature sensor? Ohm meter...nothing...reset...check...fired up and running!

The unit has been running now for 12 hours without an issue and I am praying that it will be on in the morning. I am confident it will be as it sounds great and has not run like it is since the start of this head scratcher.

I had no idea there was a small screen between the supply line and the fuel pump that may clog and trip the burner into a default.

I must say that Aquahot tech was fantastic and available, they assisted me at every step!

Hope this help someone somewhere! Happy travels!
Mike

[brobox]

Great report on the troubleshooting, thank you Mike.

[Vfaozzy]

Still running, it is fixed! Yes, Happy Dance!

[hogdriver]

Vfaozzy

I’ve had similar problems recently but the fault is intermittent and I can get it to happen often enough when a AH guy is here. Can you elaborate more, or perhaps snap a picture of where the inlet fuel screen you cleaned is located. Is it in the filter assembly?

[Vfaozzy]

...there are two fuel lines that go to the burner (fuel pump) one is a feed and one a return. Remove the feed line and there will be a screen at the point where it connects to the fuel pump...I used a compressor to gently blow out the contamination and it worked. I will be more then happy to attach pictures but I am on the road at the moment!! Hope this will get you started. Mike

[hogdriver]

Thx. I look forward to a pic

[hdgoldie]

Ours (a 400) has been doing the same thing - only way more intermittent. The unit has been serviced - tech said it was not an AquaHot issue since the unit was performing perfectly. Entegra swapped out the switches while at Perry - no joy. It's on our list of items for the factory to check at our next visit. Ours will go weeks without any issue and then turn off once or twice in a few days, then work perfectly for weeks again. We'll pass on your findings with the fuel screen. Thank you!

[fairway2002]

FYI. The control board has two power connections on it. One is main power other is remote disconnect. So if you hit sales man switch it will turn off.

If you have low power to the remote connection it will not fire the blower and turn off unit. Aqua-Hot tec support could not believe it. you can make a jumper and jump it out.

[Vfaozzy]

[Vfaozzy]

The last picture with the red circle is the return fuel line as it is the only clear picture of the fittings in the manual...remove the “S” Supply line which is identical to the return and you will see the screen that may be clogged. Follow the directions in the service manual for removal of the burner and clamping the fuel lines so they don’t spill fuel all over! Hope this helps! Mike

[Vfaozzy]

This picture should help you identify what fitting I found the screen in. Check out the other pictures I posted as well.

[brobox]

Thanks, I never would have found that looking for it.

[Magic-carpet]

I just looked at the service manual that we got in the class and it doesn't mention that screen at all. That's really a shame they haven't documented that screen and where its at. Good that you found it Mike and thanks for sharing the information.

[Gasman 2]

Gosh must of have been debris from when the Aqua Hot was installed. Wouldn’t think this would have got pass the filter in normal operation.
Yes it’s odd that the Aqua Hot’s service manual does not mention this screen.
Richard