Aqua Hot Diesel burner won't fire

[turbochaz]

Hello all. New to this forum and I see lots of great support here. We purchased an 07 Exec back in May and have been loving it ever since. We have been using the AquaHot electric side all summer for hot water, but as winter set in, we fired up the diesel side for the first time a few weeks ago. It worked fine for a weekend but when we tried to fire it up again a few weeks later, the diesel burner won't fire. According to the previous owner, the system was serviced back in January (confirmed by date on the filter). I've done some basic troubleshooting, but before I get further into it, I wanted to ask a question here. The diesel burner status light on the panel is always illuminated regardless if I have turned on the diesel switch inside the coach. In fact even if the system is completely turned off (both electric and diesel) the diesel status light is still on. My understanding is this light should only be on when the flame exists on the diesel burner. Does this automatically mean that the photo cell is bad? Just for information, the electric side works as expected, just can't keep up in these winter temps. Any help is much appreciated and sorry for the long post.

[96 EVO]

Just checked mine and no lights illuminated with both sources turned off.

[Ivan K]

A bad photo cell would not prevent the firing for initial few seconds but will kill it shortly after starting. So, if it does not fire at all, there is an other issue.

[turbochaz]

Thanks @96 EVO Doing some more research, it looks like the photo cell can be testing with an ohm meter. If it's ok, I'm thinking the controller is next.

Thanks @Ivan K That's good to know. I'm getting no burner ignition at all so I'll have to dig deeper.

[96 EVO]

Have you tried the reset button with a toothpick?

[turbochaz]

Yes I have. No change.

[Tom Cherry]

My suggestion is TWO fold.  Download the MODEL specific manual if you do NOT have it.  Then read the trouble shooting guides.  They are a bit long, but very specific.  There is a section on the burner.  I don't recall the lights being on....or more specifically, NOT being able to turn OFF the Diesel Burner light.  If you don't find a comment or a suggestion, then I would call AH tomorrow.  All the info in the past here and online is the exact OPPOSITE.  The AH calls for HEAT (water or furnace).....or the boiler temp goes down due to low ambient.  THEN the burner or the element or both.....and that depends if there is a differential thermostat.  SOME had a higher temp for the burner so that the electrical will always come one first....most of the recent ones have ONE thermostat that triggers BOTH.

Bottom line....if the burner does NOT fire, then the light may stay on for a period of time or maybe cycles.....and then turn off.  Likewise, the diesel switch triggers the fan and the burner proceeds to light and burn.  If that doesn't happen, then the light stays on for a brief (few minutes) of time and then shuts off.  When the SWITCH IS ON and the LED light is OFF, then that tells you that the burner did not fire properly and the burner needs service.  

My take.  The LIGHT IS ON means that the Burner can be "Lighted or is going to light".  So, normally when it is on and the burner is working....it is FINE and it stays in the READY state.  BUT, when you turn it OFF, that kills the signal for the Diesel to be able to be run or needs to be run....typically by LOW boiler temp and the 180 DF thermostat (used in most) calls for the boiler to heat up.  Once it is heated, then the demand for heat or hot water cycles it on and off....as does the "Normal Temp Drops".

SO, the Switch is not directly wired to the light.  It is an indicator light and when it goes off, after a NO FLAME or whatever, it turns off....

Like others, I have NOT seen a situation when the LIGHT stays ON, AFTER you turn off the Diesel switch.  Get the Model Number from the unit and if you don't find any information, call AH. They have good hands on Tech support....

 

[GranPrix]

My photocell went bad.  The first indication after the burner timed out but did not light was that the red light on the switch was blinking.  I called AH tech and the guy on the phone immediately identified the problem as the photocell.  After a $175 purchase of a new cell, (would be less than $20 for my home heater), I was on my way.

[Bob R]

There is a great site for troubleshooting your Aqua-Hot or Hydro-Hot system.  Roger Berke operates it.  The site is unbelievably helpful as is Roger.  It has been a while since I have need to use it, but I believe it is still on-line.

Aqua-Hot Questions (rvhydronicheaterrepair.com)

 

Bob

The attached file is a picture of the Control Board and its lights on my 2005 Dynasty.

Bob

AquaHot Control Board How to Read Lights.pdf

[turbochaz]

I thought I'd report back on progress here, but unfortunately I don't have a solution. I went back to the coach armed with tools and a couple new filters with the intent of starting with a new filter just because. Just for the heck of it, when I got there, I hit the diesel burner button and well, it fired right up. I ran it for about an hour, shut it down and changed the filter. After one cycle to purge the air, it again, fired right up. It is a little stinky so I'm going to order a new nozzle and replace it, as well as a burner chamber clean, next time I'm at the coach. Again, thanks for all the help here and hopefully the issue doesn't come back.