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Topic: AquaHot Diesel Light Went Out (Read 1238 times) previous topic - next topic

AquaHot Diesel Light Went Out

In cold temperatures, we keep the both diesel burner and electric heating element on.  One night recently the diesel cycle shut off shortly after it began (i.e., didn't run a full cycle).  The light above the switch also went off, which doesn't happen when the AquaHot is functioning normally. 

By the time we discovered this, the air coming through the furnace vents near the floor wasn't warm, but it wasn't as cold as outside temperatures, either.  I turned the switch off, and then on again.  The diesel burner once again failed to complete a normal cycle and the light above the switch went off.  We left the diesel off that night.  When we turned the switch on again, the next time the diesel cycle completed normally and has run like a champ since (for about a week, maybe 10 days, running several times a day and all night).

Two questions:

    • If it happens again, will the electric heating element alone at least maintain bay temps above freezing temperatures that would damage any of the systems? Single digits coming tonight worry me.
    • If I have to be away from the coach (which I must, tomorrow, for about four hours) is it safe to leave the diesel burner on? We normally turn it off, along with the water pump, if we are going to be away for any length of time.  But I'm worried about maintaining adequate bay temperatures given the forecast tomorrow.
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    As background: the AquaHot was checked and tuned-up for winter December 2015, 45 days ago — fuel nozzle, filter, and electrode replaced, combustion chamber cleaned, etc.  The unit ran fine afterward, and with the exception of this "burp," is running great again. For what it's worth (maybe nothing?), we observed this behavior once before during our PDI on the coach May 2015.  The previous owner was ready to dive into the AquaHot and do a tune-up then, but the system completed a full cycle and functioned perfectly for several cycles afterward and for the next several months.

    Anything we should be watching for?  With thanks always for the great help available from the members of this Forum!
    The selected media item is not currently available.Richard & Susan Peck
    ____________________
    1999 40' U320 "Bob Patrick"
    (2000 4010 U320 WTFE Floor Plan, Single Slide)
    Build #5567  |  MC #17522

    Re: AquaHot Diesel Light Went Out

    Reply #1 –
    When that was happening to mine when I bought it, it was the fuel line pulling air. I could re-start it sometimes and it would keep cycling. Other times it would just not start. I was able to hear the different pitch at the exhaust when it was working, like running under a load and then freewheeling.
    As for leaving it on, I have always left mine on while going fishing and other excursions.
    1999 40 ft. U-320 wtfe build 5563 Chuck & Lynda's "Rollin' Inn"  2030 watts solar
    prev. mh's 71 GMC 5 yrs. 73 Pace Setter 1 yr. 78 Vogue 5 yrs 81 FTX 40ft all electric 18 yrs. 1996 Monaco Signature 3 yrs.
    2014 Grand Cherokee Overland
    Dream as if you will live forever. Live as if you will die today.  James Dean

    Re: AquaHot Diesel Light Went Out

    Reply #2 –
    If you are plugged in turn on the electric. Depending on the temps it will keep you from freeze bays but the diesel is much better for that.
    2025 Wanderbox Outpost 32 on F600 Expedition Motorhome
    2015 Born Free Royal Splendor on Ford 550 nonslide version  for sale
    Former Coaches  covering. 360,000 miles
    1999 34 U270
    2000 36 U320
    2001 42' double slide U320
    2018 Jeep Rubicon

    Re: AquaHot Diesel Light Went Out

    Reply #3 –
    Quote from: LookingWest –
    Anything we should be watching for?  With thanks always for the great help available from the members of this Forum!

    Ping Rudy or Roger Berke.  Expert, certified AquaHot advice and they're members of the forum.  I know Rudy has walked others through diagnostics over the phone.
    Learn every day, but especially from the experiences of others. It's cheaper!  - John C. Bogle

    2000 U320 36' non-slide / WildEBeest Rescue
    2003 U320

    Re: AquaHot Diesel Light Went Out

    Reply #4 –
    Hi Susan,

    If you are low on coolant it could fail to start being somewhat correlated to the the tank temperature at the time. Let it cool way dawn and the remove the radiator cap...if you don't feel coolant with your finger placed fully inside then it is a little low. Or  low coolant sensor also could be problematic itself. Do you see the normal overflow tank fluid levels going up and down with tank temperature changes - suspect a plugged or broken overflow tube or a  bad radiator cap.

    Other problems to suspect could be an intermittent ignitor coil, weak flame sensor or failing controller box. All three of those can work, then fail infrequently. I repair the controller boxes but do not have other parts. Rap on the controller box with a screw driver handle right after it is switched on inside the RV by someone else. If you hear buzzing noises from the box or it the unit suddenly starts up - then your problem probably is controller box. Wiggle some of the controller plugs wires as a similar test too.

    Others may chime in to be more specific with some suggestions.

    Jim
    Jim Frerichs
    2002 U320 42'

    Re: AquaHot Diesel Light Went Out

    Reply #5 –
    Richard and Susan,

    Not having an Aqua-Hot but knowing the recent history with your coach, I like Jim's first suggestion.  You may have gotten low on coolant a couple of weeks ago ;-).  I'd check the overflow bottle and make sure you have the coolant topped up (may take several toppings) and then monitor and see if the problem repeats.

    Rich
    Rich and Peggy Bowman
    2002 U270 3610 WTFS, build #5939--"Freedom"
    2022 Jeep Grand Cherokee Summit 4xe
    SMI AirForceOne brake system
    PakCanoe 15

    Re: AquaHot Diesel Light Went Out

    Reply #6 –
    Big thanks, everyone, for suggestions and pointers to things I should check! 

    Will update you as we learn more.  While I was outside an hour or so ago, I was happy to hear the AquaHot fans behind the utility bay and to feel the heat.  Don't think I ever noticed in moderately cool temperatures, but it's sure easy to know that your bays are heated when you are standing in 15-18 degree air and open a bay to do something (in this case, double-check the improvised hole seal/plug around our 50 amp cable).

    With thanks to all, always!


    Richard & Susan
    The selected media item is not currently available.Richard & Susan Peck
    ____________________
    1999 40' U320 "Bob Patrick"
    (2000 4010 U320 WTFE Floor Plan, Single Slide)
    Build #5567  |  MC #17522

    Re: AquaHot Diesel Light Went Out

    Reply #7 –
    You do not mention the exhaust of the heater being smokey when it is firing.  The recent service should result in a clean firing exhaust.

    So a shut down while burning is something else beside the nozzle.  Intermittent issues are the devil to diagnose.  But things that could cause a shut down while burning for your vintage heater (431/12) are Control Unit loosing control of heater while it is burning or Flame Sensor's resistance goes up as it burns and finally the Control Unit thinks the Flame Sensor is signaling there is no fire and stops the fire and faults the burner (turns inside light out).

    The Flame Sensor voltage can be observed while the burner is firing to see if the voltage is steady or does it slowly fall.  The Control Unit can be replaced with a loaner one to see if intermittent faulting stops.

    I did not hear you say the burner failed to fire for a new cycle but rather stopping while firing during a cycle.  Failing to re-fire would bring the Ignition Coil into the picture and a loaner coil would be needed to check that possibility out.  One can test fire a coil 100 times to see if even on time the coil misfired.  If so, replace.  But this is not a perfect test like a loaner one is.

    One would need to run the loaner parts long enough to see if problem goes away which can take a day or more.  Others will be able to watch the Flame Sensor voltage with a VOM meter and some time sitting there.  Having loaner parts is another matter.  I do as I do not like to be in the throw parts at it till we get the right one business.  If I can loan all of the above parts to sort the problem out, I bet there are others that can too.

    Lastly, sucking air caused by cracked supply fuel line that stops the burner from firing results in lots of white smoke before the firing stops.  So again, a clear exhaust eleminates that.  One does need one fourth of a tank of diesel or more to run the Aqua Hot diesel burner.  If close to one fourth mark, fuel up real soon.
    Rudy Legett
    2003 U320 4010 ISM 450 hp
    2001 U320 4220 ISM 450 hp
    1995 U320 M11 400 hp
    1990 Granvilla 300 hp 3208T
    Aqua Hot Service Houston and Southeast Texas

    Re: AquaHot Diesel Light Went Out

    Reply #8 –
    Rudy,

    Thanks very much!  Yes, we have clean-burning/no smoke exhaust. And the burner has always re-fired, even after a premature stop. So, if we understand correctly, that seems to point to the control unit/flame sensor.  And the pattern of behavior (if we're qualified to recognize a pattern) would be consistent with the flame sensor believing there was no fire and faulting the burner.

    As always, the help you provide is precise, well-informed, and generously given. Very grateful!  Our current travel plans, assuming no changes, are to cross from the Carolinas to Arizona in February.  Count on a visit from us — not so much for a look at the unit (although that would be great, if schedules permit), but to says "thanks" in a more personal way than posts permit.



    Richard & Susan
    The selected media item is not currently available.Richard & Susan Peck
    ____________________
    1999 40' U320 "Bob Patrick"
    (2000 4010 U320 WTFE Floor Plan, Single Slide)
    Build #5567  |  MC #17522

    Re: AquaHot Diesel Light Went Out

    Reply #9 –
    We will be here so stop by, I know where the locals go to eat real good.  Safe travels
    Rudy Legett
    2003 U320 4010 ISM 450 hp
    2001 U320 4220 ISM 450 hp
    1995 U320 M11 400 hp
    1990 Granvilla 300 hp 3208T
    Aqua Hot Service Houston and Southeast Texas

    Re: AquaHot Diesel Light Went Out

    Reply #10 –
    Yup, Rudy sure does know the local spots, the Barbcue he took me to, lil west of Baytown was the best, but many more great spots, try some seafood too.
    Dave M

    Re: AquaHot Diesel Light Went Out

    Reply #11 –
    Put this in the "For What It's Worth" category.

    We had our Hydro-Hot serviced at MOT last October for the first time since we purchased in May of 2014. Everything was fine until we left on our current trip. We had the same symptom: The diesel light went out and no heat from the Hydro-Hot.

    Checked with MOT on our way out and they indicated they had had some bad nozzles. They checked, and sure enough the nozzle was not functioning correctly. Had that replaced, had them show me how to do the replacement on the road and bought two extra nozzles and stored them in the bay if needed. Cheap insurance.

    Don
    2007 Nimbus 340 quad slide
    Build #6386 FMC #17360 FMCA #441779
     

    Re: AquaHot Diesel Light Went Out

    Reply #12 –
    Just an update, with ongoing thanks for all the suggestions/guidance:  AquaHot has been running like a champ since it's "burp." That's more than we can say for the weather!  But the coach has been completely comfortable, and the bays have stayed in the 40-degree-plus range, since plugging the area where the 50 amp power cable exits.



    More Foretravel-in-the-snow photos, if someone can let me know how to post a link to our album of uploaded photos in the "Media" section of ForeForum.  :-)
    The selected media item is not currently available.Richard & Susan Peck
    ____________________
    1999 40' U320 "Bob Patrick"
    (2000 4010 U320 WTFE Floor Plan, Single Slide)
    Build #5567  |  MC #17522