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Topic: Aqua-Hydrohot diesel cutoff problem (Read 983 times) previous topic - next topic

Aqua-Hydrohot diesel cutoff problem

For you aqua/hydrohot experts - My hydrohot (HHE-09E - 12 vdc) runs fine on electric with no faults. 

The problem just started with the diesel.  I turn on the diesel switch (electric off) and the diesel switch lights up (normal).  Then the blower starts and the diesel fires up (normal).  It is in the 80s here so I'm not sure how long it would take the coolant to reach 190 but in about 2 minutes the diesel switch light goes off (not normal) and the diesel stops. 

The motor then runs for about 2 minutes (usual purge cycle - normal) and shuts down.  BUT the unit is still humming - and I can feel a slight vibration when I place my hand on the galvanized box (I'm guessing this is bad).  Then when the diesel switch is manually toggled off the hum goes away.  There are no faults on the electronic controller.  I have repeated the whole process 3 times now and it does the same thing. 

Any ideas on what could be the problem?   
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: Aqua-Hydrohot diesel cutoff problem

Reply #1 –
Mark, send Rudy Leggett a note on here. He's awesome and will be the only person that touches our aqua hot ever again! 
Tom & Bill

2013 Jeep Grand Cherokee

Re: Aqua-Hydrohot diesel cutoff problem

Reply #2 –
Is Rudy in Houston?
Tim Fiedler    2025 LTV Unity MBL on Order
2000 Chevy Tracker 2 Door Convertible 4WD Now lifted 4.5"
1985 Citroen 2CV6 Charleston
Murphy Rebel on wheels with 175HP Titan
Cessna P337
1980 48' Westport MY (!/4 Share)

Re: Aqua-Hydrohot diesel cutoff problem

Reply #3 –
Hi Mark,

I am in Nac on my way back to Houston and will arrive there this weekend, I think.

Now, can you please verify that your burner is actually firing and putting out hot exhaust for two minutes and then the fire goes out and a shut down purge occurs.

Also, what lights are on your electronic control board when the diesel shuts down?
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: Aqua-Hydrohot diesel cutoff problem

Reply #4 –
Rudy watches this forum as he is an owner too. I am sure he will see this.
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: Aqua-Hydrohot diesel cutoff problem

Reply #5 –
Quote from: Rudy –
Now, can you please verify that your burner is actually firing and putting out hot exhaust for two minutes and then the fire goes out and a shut down purge occurs.
Also, what lights are on your electronic control board when the diesel shuts down?
1 - No lights on controll board - electric & diesel off
2 - Turned on the diesel - burner fires with hot exhaust and runs for 90 secs this time
    Lights on - diesel burner, pump 2 & 3, heating status
3 - 30 seconds into 90 seconds of burn the low temp cutoff status light turns on
4 - 45 seconds into 90 seconds of burn the pump 3 light goes out
5 - At the end of 90 seconds the diesel toggle switch light in the coach goes out and the diesel burn stops with a small amount of white smoke. 
6 - Purge cycle continues for the next 2.5 minutes blowing warm air then stops.  The following lights remain on - diesel burner, pump 2, heating status, low temp cutoff status
7 - I let the system continue for 15 minutes in this state and it continued humming.
8 - Finally, turned off the unlit diesel toggle switch in the coach and the humming stopped.  All lights turned off now except the low temp cutoff status.

Hope that is a more helpful description of what's happening.
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: Aqua-Hydrohot diesel cutoff problem

Reply #6 –
Mark,

I have the great good fortune of being able to consult with Roger Berke to aid my diagnostic skills.  He has again shared his thoughts to go along with mine to give you the most complete list of possible problems.

Do you have more than 1/4 tank of fuel.  Low fuel creates a fuel issue.

Clogged nozzle is another fuel issue that can stop the flame after ignition.

A failing flame sensor will allow the flame to start and then turn if off prematurely as will a good flame sensor that is dirty or sooted.

Lastly, the control board could be the culprit as Roger noticed the pump 2 being on during the burn.  Pump 2 should be on only if the zone thermostat is calling for heat.

Pump 3 is correct as it is the stir pump.

Hope this helps.  I sent you a PM with my phone and you are welcome to call if you wish.

Thanks again Roger for the assistance.
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: Aqua-Hydrohot diesel cutoff problem

Reply #7 –
Thanks Rudy and Rodger.  I'll check your PM and investigate more tomorrow.  Got a full tank.  Just had it serviced so nothing should be clogged and I talked to the tech and he said he cleaned the flame sensor... so that may leave the control board?$!?$?

It is dark now in this part of New York so I have to rest!  I really do appreciate all the help.  You guys are the best! 
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Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit

Re: Aqua-Hydrohot diesel cutoff problem

Reply #8 –
Update: 

I had the distinct pleasure to be instructed by Rudy.  He took an unbelievable amount of time to work with me to troubleshoot and diagnose the problem.  I am no longer a neophyte and can at least disassemble/reassemble my hydrohot.  He consulted with Roger and they gave me the courage and tools to resolve the issue.  And I did!

The result is that the unit is now performing normally and not shutting down prematurely.  The flame sensor is now seeing the light and has operated normally for the last day!  I have hope.  Thanks to Roger for pointing me in the right direction to solve the issue and thanks to Rudy who worked with me over the phone to guide me patiently. 

These guys are an amazing resource.  I am a convert.  If you need help with aqua-hot/hydrohot issues these are the goto guys.
The selected media item is not currently available.

Mark & Mary Benko
Former coach: 2005 U295 3823
Jeep Cherokee, Honda Fit