Aqua Hot non start

[Adam Hicklin]

I've been chasing a temperamental, non-lighting (on Diesel) AquaHot problem for a year now.  Has been working fine for the last few months.  Sat for about a month then wouldn't light.  Was doing some tests via Roger Berke's website (high limit stat-OK, correct voltage tested through plugs, fuel-OK, nozzle and gap done 6 moths ago). Through the testing, something happened and it lit.  Lots of white smoke at start then settled in to perfectly functioning AquaHot.  This would lead me to believe lose connection? Stuck relay?  I have no idea.  Any suggestions on starting point?

[Fred Brooks]

      Adam,
I've been chasing your situation since Aqua Hot's became popular in the 90's on luxury coaches. Trouble-shooting is a "divide and conquer" attitude approach. The most frustrating part is when all of a sudden it decides to start working. My thoughts are "things that move only move so many times and then they quit moving" (kinda like us eventually).
       T-stats and limit switches are bi-metal that click back and forth to make or break contacts. It doesn't take much to disturb one that is on the verge of activating. Sounds like you where in the area where the diesel and 120volt t-stats and limits are located. I would let it set for a while and try to get it to fail again. then start to carefully check for an "open circuit" (no continuity) thru the diesel t-stat or limit switch. Another thing to check is loose fitting female spade connectors fitting onto the limits and t-stats.
    If all fails, contact Aqua Hot in colorado. Their tech support is great and can guide you on your adventure. Have the model and serial number ready. 800-685-4298
       Happy Trails, Fred

[Darrell Terry]

Adam,
 I went through the same trial with my Hydro-Hot recently. Sometimes it would light, sometimes not. Sometimes it would light and heat to limit and then refuse to light again when temperature dropped while using shower. At times it would work fine for a week or three and then begin to act erratic again.
After swapping out high limit switch, flame sensor, and control box without success, it turned out to be an intermittent coil.
Replaced coil and all is well again.
Darrell Terry
2004 Beaver Monterey

[George Harwell]

Ditto mr. Terry's story. Mine was intermittent for over a year. Troubleshooting led to the burner control box but it failed shortly after replacing the box. Coil finally died so replaced it and no problems since. They can be pesky. Good luck.

[David T. Richelderfer]

The igniter coil on our unit had to misfire before the warranty would cover its replacement.  My repair tech, Mike Flowerday, had to start and stop the burner numerous times before it finally misfired.  The problem is those igniters seem to misfire more frequently when cold.  (Obviously that could read "when needed" instead of "when cold.")  When the warranty representative was on site it was in the afternoon after warming up in the sun... and the igniter wanted to work well when 70F outside.

[Steven Hoffman]

Adam

When working on an Aqua Hot I find it beneficial to follow it's start up sequence.
1  Indicator lamp on
2  Motor in Aqua Hot starts
3  After about 10-25 seconds solenoid valve opens fuel is sprayed into combustion chamber.
At the same time the electronic ignition unit produces high voltage and the fuel-air mixture in the combustion chamber is ignited by the spark on the ignition electrodes.
4  The flame is detected by the flame detector then the electronic ignition unit stops producing high voltage and combustion continues on its own
5  When temperature is reached fuel solenoid shuts off and 150 second run down starts.

By listening and watching when it is trying to start you can get an idea where to start looking.

If it is going through the start up procedure but not igniting then it will shut down.  There will be a small quantity of unburned fuel in the combustion chamber from the unsuccessful start attempt.  If you get it to start on subsequent attempts you will get the white smoke until the accumulated fuel burns off.
 
Pin 8 on the control unit should provide voltage to the coil during the start up sequence.  If your not getting voltage there at start up then look at things like the fuel pressure, high limit switch, flame sensor, and control box.  You can open the burner head and supply DC voltage to the coil + black wire, - brown wire.   Electrodes must be connected.  Do not energize for more than 15 seconds.

Good luck
Steve
 

[Edward Buker]

The intermittent igniting can be maddening to sort out. If you have recently had a service with a new nozzle I would start there. The fuel pattern is fixed by the nozzle geometry and it is not an exact science that the pattern will precisely come close enough to the electrodes to ignite every time. Nozzles are cheap and Roger has changed his source to Danfoss Brand because they have been more reliable over time.

Regarding the other folks input  about the coils, they are problematic. These are not like a car coil, they run on straight DC voltage and have a built in oscillator circuit to generate the primary waveform that gets stepped up in the secondary winding. It is a marginal design that is prone to fail. The test is to take a 12V battery (I used my Makita drill battery) and connect it and disconnect it 100 times on the bench and if one time the electrodes do not fire then buy a new coil. This cured my intermittent firing problem. A new nozzle helped also.

Regards Ed

[Adam Hicklin]

Thanks for the input.  Following Steve's process...the AH motor starts.  Seems like I hear the fuel valve open (at this point when it is working you can hear the "whoosh" as the fuel ignites). When not working you just hear the motor continue to run, then shut down.  I would guess it is an ignition problem because as Steve said, when it does finally fire, (after trying it several times) I get the big cloud of white smoke.  Yesterday when it finally did fire, once the smoke cleared, it ran perfectly.  Nice and clean. I left it on overnight and all day today, flawless.

Ed, so are you saying take the Wabasto off, hook up the igniter on the bench and supply 12V to it repeatedly?  Would a car battery work?  I don't think I have any 12V Makita batteries anymore. 

Thanks for your help guys.  I have a couple more things for which I'll need the Forum Expertise.  One thing at a time though.

[Edward Buker]

Yes, any 12V DC source will work. If I remember right I pulled the electrode set with the ceramic probe holders and the coil and set them up on the bench. There is polarity to the coil, so be sure to hitch + 12V and ground properly and then keep pulsing the source voltage on and off. Mine would miss about once every 30 to 50 times that I applied voltage and when I tested the new coil the same way, no misses and once installed no problem anymore. The smoke on start up indicates that you have no fuel feed issue, that is unburned fuel. You could still have a nozzle issue with the pattern, but not a supply issue.

Later Ed