Aquahot shutting down prematurely

[Dwight Wilson]

Hi Folks,
Recently the Aqua Hot burner in our 05 Patriot Thunder has been shutting down after about 5 minutes on Diesel. All indicators on the control board are green but the inside indicator lamp goes off at the same time the burner shuts down. The Aqua Hot does not fire as long as the switch is in the "On" position with the light out. If I return the switch to off and then back to "on" the inside green indicator lamp comes back on and the cycle returns as normal except shuts down after about 5 minutes. The water heats up but the system will not re-light unless the switch is manually shut off then on again when the coolant temp drops. No white smoke on either the start up or shut down, and  there does not appear to be any water in the filter. This is more of an inconvenience than anything but I know this is not normal so am looking for suggestions. A full service (nozzles, adjustments, filters, etc.) was performed by an approved service centre prior to starting our tour in October but we have been using it quite a bit over the last 4 months during our travels. In case I need a tech, we are currently in San Diego until the end of March so if you know of a good mobile service rep in this area please forward a name.
Thanks for any suggestions,
Dwight Wilson,

[George H. Wall]

Dwight, I have the SAME problem with my HydroHot in my 2002 Patriot. This also happened after nozzle and filter change by an approved certified AquaHot tech. I also am looking for a solution!!!   Henry

[Edward Buker]

Dwight,

There may be some clues in the way it shuts down. If the fuel is shutting down then the burner blower will continue to run until the flame sensor shuts it down which has a delay. If it sputters and sounds like it is not burning properly then a nozzle could be plugging. The ignition coil could be failing and as it heats up in use. If it is burning properly and just sharply cuts off without any cool down cycle it may be losing power due to the controller box failing that is on the side of the burner. There may be some better electrical diagnostics for your unit in the specific Aqua Hot service manual for your unit that could help sort out what is going on by some electrical measurements.

That being said I like to start with what is least expensive and I would check that all 12V electrical connections to the burner and boards are tight. I would set the electrodes, change the nozzle and filter, and at the same time be sure that the safety sensor face is clean and not cracked. That would rule out the simple things that can interrupt the flames performance. Poor nozzle patterns are probably the most likely cause of burner performance issues, cut out, or more often failure to ignite.

Later Ed

[Stan Simpson]

I also had this happen to me. The tech diagnosed it as a failed temperature sensor. I don't remember if it was the high or low. When he replaced it, the problem went away.

The controller box was the next thing to go and it has been replaced.

Knock wood, our Hydro Hot is working fine right now.

Stan

[Dwight Wilson]

Thanks for the advice. The burner shuts down but the delay continues to operate as if I had turned the interior switch off so am thinking the fuel  is shutting off pre-maturely. I will check the connections on the mother board tomorrow. We were in Palm Springs prior to this developing and of course the dust is like talcum powder so it is possible some of the connections became contaminated.
Regards
Dwight

[Roy Warren Co-Admin]

If you are in Palm Springs, Mike Flowerday is usually there.  If you can't find his phone number, you can call me and I will give you his number.
Roy Warren

[Edward Buker]

Dwight,

As Stan mentioned the over temp sensor could be failing. The normal shut down cycle would mean that the silver burner control box is probably not the issue. Seems like something is telling the burner to shut down. Check the schematic for your unit and you may be able to reason out if the 12V over temp sensor was opening early at a lower temp, would the burner go through a normal shut down cycle. It would make sense that it would. Another way to diagnose this would be to use an IR gun on the filler neck of the boiler and see if it is always shutting down at the same temp like a thermostat is opening a circuit. This over temp sensor should be able to be measured and diagnosed with a DC voltmeter. Sometimes these sensors are diagnosed by heating water and measuring with an ohm meter if the contacts are closing at the required temp limits. Keeping it simple, these sensors are not that expensive, might be worthwhile to just order one and change it to rule it out.

Later Ed

[Dwight Wilson]

Great advice Ed,
I am leaning in the direction of faulty thermostats so will try to source same in the San Diego area.
I will advise any progress for any experiencing similar issues.
Thanks,
Dwight

[Dwight Wilson]

Update, Changed the High Temp AC thermostat as that was the one that was corroded, and now the electric element portion of the boiler is working fine. I need to acquire another thermostat to replace the high Temp DC one which I believe will resolve the diesel operation as this one also appears corroded. Apparently they are both the same unit as per the service tech I spoke with at Aquahot . They are easy to replace as they do not penetrate into the boiler (Aquahot AHE100- 03s) so there is no need to drain any fluid. Cost is about $50.00 each from a dealer in Escondido California.
Will update again once I get the other thermostat installed.
Thanks for the suggestions,
Dwihght

[Dwight Wilson]

Update, received another thermostat to replace the 12V one as well which I believe controls the Diesel burner. The 12v and Ac high limit thermostats are the same part BTW on my Aquahot. Both of these screw into the tank wall but not into the boiler so they are easy to replace. Hasn't resolved the problem yet but I also bought the 185 degree Control thermostat which goes into the boiler so I think I will need to drain or pump out about 1/2 the tank before I take out the old one. We are still getting heat so I may just wait until we get home and let the dealer look after this as I still have an extended warranty.

[George H. Wall]

Dwight, Let us know how your problem is resolved!  Henry

[Edward Buker]

Dwight,

I do not believe that there are any thermostats that extend into the water jacket. There are 4 button external thermostats, two for the AC and two for the DC circuit control. The only thing I know of that contains wires that extends into the jacket of the boiler is the 120V heating element. I looked at the 100-02s manual which I think is the same as the 100-03s configuration but I am not absolutely sure of that.

I think the DC and the AC circuit just has two button thermostats each in series, one is the control thermostat that calls for heat when the temperature is too low and one for over temp that will open if too hot just in case the control thermostat fuses shut. You need to change both of the DC side button thermostats and see if that is your cure.

Later Ed

[Dwight Wilson]

Maybe the 03S is a bit different as I have a part number ELE-014-005 "Thermostat, Control 185 degree, 1/2 , NPT thread". I know the thermostats on this are a different version than the 02S and after looking at an 02S manual online I agree there does not seem to be one of these Control units. The tech at the dealership where I purchased the other thermostats suggested I also pick this up (About $60.00). Not sure exactly what it does but it does penetrate into the tank.
Dwight

[Edward Buker]

Dwight,

I do remember that some models had a fluid level sensor as part of the shut down system. I just looked at your parts manual and indeed there is a float sensor which is wet and a probe type temp sensor with 1/2NPT threads. Standard boilers I have worked on have had a welded tube that probes used as aquastats like this go into and were not actually wet probes. Not sure what Aquahot did here. I would call them and ask if your boiler needs to be drained to change that probe out. For diagnostic purposes you can bypass the sensors one at a time and see which one is shutting the system off prematurely. Hope this helps.

Later Ed

[Jeremy Parrett]

Coachella Valley California for Aquahot, Hurricane,  etc service    Howards RV Repair  909 227 3904.
Wayne is a busy guy but a good tech.