Hydrohot - Hot Water, No Heat

[Liam Gray]

We bought an 05 Monterey a month or so ago. and we're still working out some kinks. My plsan this weeken was to replace faulty inverter and leaking skylight, but the RV ad other plans.

Up until this weekend the Hydrohot worked great. Now we get hot water but no heat to any zones. Today I tried jumping the thermostat at the Hydrohot, but no response. I jumped the fan and the fan fired up, but no response from the pump. The stir pump is working fine, and I dont have any fault indictors on the board. I tried the low volt reset to no avail, tried killing all 12v and 120v power to see if that might reset things, but no luck there either. Coolant is right where it should be. I also noticed that while we do have hot water, the unit runs constantly now instead of cycling on/off as it did previously.

My gut says the board is bad, but I dont know enough to be certain. I can get a refurb board for $375, or I can call a mobile tech who actually knows what hes doing, but will likely charge $375 to tell me I need a new board. Regardless, I'm sure I will make the wrong choice. If the board was $100 I would just throw the part at it, but $375 is a bigger pill to swallow. Any ideas?   

Thanks!
Liam

[David T. Richelderfer]

You did not indicate the model of AquaHot(?) your coach has.  Mine is the 02S.  You have hot water at the faucets, so I will assume the diesel burner or the 120v electric element is heating. Which is it, one or both?

If you do a search on this Forum, as I have many times, you will find threads that indicate the water pumps built into the Aquahot will stick.  Try tapping on the pumps to dislodge the impellers.  It seems likely that one pump may be stuck but not all three pumps.

When you turn on the interior furnace heaters, do their fans turn on? If the thermostats are calling for heat, the associated fans should turn on immediately.

You said the AquaHot does not turn off once it gets going.  If so, does its heated water just get hotter and hotter.  The Aquahot has four coolant temperature sensors.  Perhaps one or more of the sensors is not functioning.

I just had our o2S Aquahot fixed (again).  Last time the tech replaced the control box.  It worked less than a half dozen times.  This time he replaced the coil and so far, so good.  Its problem was the burner would not ignite but the electric element worked well.  The electric element heats enough water for a shower or two, and to wash dishes but not for heating the coach interior using the furnaces.

[Steve Huber Co-Admin]

To follow up on David's comments, with the thermostat's calling for heat from the HH, remove one of the grills and see if the hoses are warm/hot. If so the problem may be electric.
Steve

[Eric Maclean Co-Admin]

Liam
As David stated you need to identify which model of Hydrohot you have and then go to the coach assist section of the form and find the service manual
That will help you familiarize your self with the operation of the unit.

You stated you have no coach heat  can you tell us if as David asked does the diesel burner run properly
Do the circulation pumps all work ? Do any of the wall thermostat invoke a response (ie) circ pump, heater fan etc.

Some of the Hydrohot units had a low temperature switch on the domestic hot water system which would cut off the coach heat to prioritize hot water production.
Your control panel should have an indicator light marker ( LOW TEMPERATURE CUTOFF) if this lamp is lite the system will not allow interior heating system to function
If this switch goes bad you won't have coach heat but the hot water will still work.
This switch can be bypassed to confirm you problem. The switch is located on the back of the unit next to the tempering valve.
In the service manual it will tell you which pin to jump at the board to test this.
On the main board the connections are marked ETCO -1 and ATCO-0  on the J3 connector.

Hope this helps
Eric

[Joel Ashley]

I have to agree that the Low temp switch is suspicious, as it keeps heat out of the coach until hot water is maxed, so you don’t run out in mid-shower.  As Eric notes, it can be jumpered on the control board in the HydroHot bay to help confirm its failure.  You likely have a Hydro-Hot model similar to ours (HH-200-09E), so check out this service manual, start on page 42, then review attendant low temp switch troubleshooting following page 85.

https://library.aquahot.com/wp-content/uploads/2022/04/HHE-200-09E_HHE-500-09M_Service_Manual.pdf

Joel

[Mark Hoovler]

On the subject of no heat from the Hydro hot.  I have the HHE-200-09E in my 06 Monterey.  During the fall service I noticed the frame on the fan/burner was cracked.  Now it has broken completely.  Having tried the heating guy in CO. at HeatmyRV.com.  He will not sell parts to anyone living in CO. if you are not tax exempt.  So I went to Hydronic heating warehouse and ordered the parts in beginning of September.  Still have not received the parts and I am worried they are blowing me off.  Is there anyone who knows of a place to buy these parts?
Frustrated in Colorado

Mark

[Dan Johnson]

Try Lloyd De Gerald services in Arkansas. He serviced mine at a rally. He is a no bull  king of guy