IEMan 1 Posted July 25, 2023 Share Posted July 25, 2023 Our Aqua-Hot 100-04S stopped making very much hot water. We usually keep the electric on and have plenty of hot water for dishes and showers. Turn on the Diesel if we want a long shower or multiple showers. Now all of the sudden we have enough hot water for about 2 minutes and then cold. If we turn on the Diesel, it fires up the burner just fine but just for about 3-4 minutes and then shuts off. The switch lights remain lit. It will re-heat again but just a small amount of hot water. It's as if we now have a 1/2 gallon hot water heater. Any suggestions? Link to comment Share on other sites More sharing options...
vito.a Posted July 25, 2023 Share Posted July 25, 2023 Check the boiler fluid level. The incoming water temperature has a lot to do with how much hot water you have. Are you using water from a shore hookup, or your onboard fresh water tank? Try filling your fresh water tank the day prior. This water will warm up to the bay temperature overnight. Then try using water from the onboard tank. Link to comment Share on other sites More sharing options...
IEMan 1 Posted July 25, 2023 Author Share Posted July 25, 2023 Hello, Boiler fluid is full, I check it weekly. As far as incoming water temp,, this has been this way now for the last 3 RV Parks shore water and it's the same at all of them. We have been in the RV for the last 3 months and this just started happening. It has been working great before. Link to comment Share on other sites More sharing options...
IEMan 1 Posted July 25, 2023 Author Share Posted July 25, 2023 Another thing I can mention is there are no red lights on the front panel either. I really hope y'all can help me out. I greatly appreciate this site. Link to comment Share on other sites More sharing options...
Vince Toscano Posted July 25, 2023 Share Posted July 25, 2023 Did you check the temperature switches, mounted on the Aqua hot boiler tank? There are 4, 2 for the electric side and 2 for the diesel side. there is a low side when to turn on each and 2 to turn of either of the electric or the diesel. Link to comment Share on other sites More sharing options...
IEMan 1 Posted July 25, 2023 Author Share Posted July 25, 2023 Hi, I do not see any temperature switches from the bay. Are they inside the unit itself? I can't find mention of them in the owner's manual or the shop manual either. How do I go about finding the switches? Or, even find out if they are on my model? Link to comment Share on other sites More sharing options...
96 EVO Posted July 25, 2023 Share Posted July 25, 2023 (edited) Believe he's speaking about the thermostats. They signal the heating source (elec element, or diesel burner), when to turn on or off to maintain your boiler fluid within a determined temperature range. Edited July 25, 2023 by 96 EVO Link to comment Share on other sites More sharing options...
Jdw12345 Posted July 25, 2023 Share Posted July 25, 2023 You can down load the maintenance manual on line and go through the trouble shooting steps and it will point you to the issue. You will have to take the cover off of the Aqua Hot and know how to use a multi meter and read the trouble shooting guide, make sure you turn off the power (120volt) when instructed! I had a problem with mine last winter and it ended up being the high limit switch on the 120 volt side! Just make sure you understand what you are doing! 1 Link to comment Share on other sites More sharing options...
Vince Toscano Posted July 25, 2023 Share Posted July 25, 2023 Yes they are under the cover. Make sure to disconnect the power. The 4 switches are about 1" diameter. 2 wire connections each. It sounds like it's the 2 temperature switches associated with the diesel side of the controls. You can go to aqua hot web site and down load the manual. Just need you model number. Link to comment Share on other sites More sharing options...
Guest Ray Davis Posted July 25, 2023 Share Posted July 25, 2023 It could be the stir/circulation pump, the symptoms are there. Here is a thread you may find helpful. https://www.irv2.com/forums/f54/hydro-hot-stir-pump-320804.html Hydro hot/Aqua hot same problems Link to comment Share on other sites More sharing options...
96 EVO Posted July 26, 2023 Share Posted July 26, 2023 1 hour ago, Ray Davis said: It could be the stir/circulation pump, the symptoms are there. Here is a thread you may find helpful. https://www.irv2.com/forums/f54/hydro-hot-stir-pump-320804.html Hydro hot/Aqua hot same problems Good idea Ray! Reminds me I planned on checking if my stir pump starts while running hot water on electric power. It doesn't run while warming up on electric, unlike the burner, but I believe it's supposed to run when there is a hot water demand. This is on a newer 450-D model. Link to comment Share on other sites More sharing options...
Jonbrooks Posted July 26, 2023 Share Posted July 26, 2023 There is also a mixing valve that is adjustable and set at the factory to provide the right hot water temperature. Mine was bad when I pulled the unit from the coach to rebuild. check if the heat zones come up to adequate heat on the furnace setting. Link to comment Share on other sites More sharing options...
David Pratt Posted July 26, 2023 Share Posted July 26, 2023 The Aqua Hot 100-04s Boiler has only three thermostats. The thermostats are located behind the Removal-able Square Cover located in the boiler above the burner. The two lower thermostats are the High Limit, 120VAC and next to it is the High Limit 12VDC. Above them is the controlling thermostat-(185deg)-this controls the temperature of the water when you are on either Diesel or Electric and will cycle on/off as hot water demand is needed. What you are describing may indicate that the controlling thermostat is failing as it is effecting both the diesel and electric operation. The simplest way to verify this is to access the thermostats and check for continuity on all three. All the thermostats should read closed when the system is cold. If they all read closed next disconnect the two wire connectors-( they are spade connectors)-going to the controlling thermostat and jump them together and start the Aqua Hot. If the Aqua Hot stays running then you have a bad thermostat. All three Thermostats must check closed when the system is in the cold state for the system to work. The high limit thermostats will shut the system off when the water temperature reaches 200degF when on diesel or Electric. If you do not have the Manuals you can download them from the Aqua hot website or I can send them to you. 1 Link to comment Share on other sites More sharing options...
Dr4Film Posted July 26, 2023 Share Posted July 26, 2023 (edited) 21 hours ago, Vince Toscano said: Did you check the temperature switches, mounted on the Aqua hot boiler tank? There are 4, 2 for the electric side and 2 for the diesel side. there is a low side when to turn on each and 2 to turn of either of the electric or the diesel. On the Aqua-Hot 100-04 which the OP has there are only 3 "temperature switches" aka thermostats not 4. One for controlling BOTH the diesel and electric assist and one each high limit thermostat for the diesel and electric assist. Ray's suggestion sounds like the most probable cause for the lack of hot water as the boiler fluid is not fully heating up throughout the 15 gallon tank. Didn't realize that Dave P. had made a post while I was writing mine. His recommendation also sounds like a probable cause as the diesel or electric assist is shutting off prematurely before it has had time to fully heat up the boiler fluid. Edited July 26, 2023 by Dr4Film Additional information Link to comment Share on other sites More sharing options...
MalcolmH Posted July 28, 2023 Share Posted July 28, 2023 In my case the lack of hot water was a failed tempering valve. The valve was not seating and allowing cold water to constantly drain cold into the hot water water supply when ever a hot water tap was turned on. The tempering valve is a miniature mechanical spring/bimetal thermostat, similar to a car radiator control. Very difficult to get to for trouble shooting. Hope this helps with solving your problem. Malcolm Link to comment Share on other sites More sharing options...
Dr4Film Posted July 28, 2023 Share Posted July 28, 2023 Would be nice to know what the outcome was for this problem. 2 Link to comment Share on other sites More sharing options...
IEMan 1 Posted July 29, 2023 Author Share Posted July 29, 2023 Just to give an update. I checked the continuity on the 2 high limit switches when cold. there is continuity. I checked the continuity on the spade connectors on the control thermostat and NO continuity. Does that test it or do I have to jump those 2 spade connectors together to see if it keeps running? Link to comment Share on other sites More sharing options...
David Pratt Posted July 29, 2023 Share Posted July 29, 2023 Yes, If the water is cold in the boiler and the control thermostat is open it indicates it has failed. Jump the two spade connectors together and it should stay running. 1 Link to comment Share on other sites More sharing options...
Dr4Film Posted July 29, 2023 Share Posted July 29, 2023 Depends on your test. As Dave stated, was your boiler fluid cold when you tested the Control Thermostat? If not then the test needs to be repeated when the fluid is stone cold. Typically, the Control Thermostat should read Continuity when cold, CLOSED contacts, then when it gets to temp the contacts will open, no continuity. Link to comment Share on other sites More sharing options...
IEMan 1 Posted July 29, 2023 Author Share Posted July 29, 2023 I just checked it when cold. All 3 have continuity. Do I jump the spade connectors on the control thermostat side or the other 2 wires? Link to comment Share on other sites More sharing options...
IEMan 1 Posted July 29, 2023 Author Share Posted July 29, 2023 I watched inside as it ran for about 3-4 minutes this time before shutting itself off. There was smoke coming from and around the yellow tube in the picture on the bottom. Smells a little like maybe some boiler fluid. Not able to see exactly. Link to comment Share on other sites More sharing options...
David Pratt Posted July 29, 2023 Share Posted July 29, 2023 I am confused1 You stated that you tested the control thermostat when you checked the High and Low thermostats cold. You stated that the high and low limit thermostats had continuity and the control thermostat was open. Now, you tested it again and you have continuity. You connect the two wires that go to the unit and not the two wires that go to the control thermostat. Consistent and correct info is a must to be able to correctly diagnose a problem. Link to comment Share on other sites More sharing options...
Ivan K Posted July 29, 2023 Share Posted July 29, 2023 Maybe too obvious but when you said that you check the coolant level, did you mean through the filler neck or just the overflow tank? Link to comment Share on other sites More sharing options...
96 EVO Posted July 30, 2023 Share Posted July 30, 2023 Hard to tell from your pic, but is that the dreaded plastic drain fitting they installed in a couple of model years? Link to comment Share on other sites More sharing options...
IEMan 1 Posted August 15, 2023 Author Share Posted August 15, 2023 Hi all, Ok, I am back able to look at my coach's AquaHot again. I started from scratch now. Tank is full of boiler fluid. When not all the way hot water, (It's 103 degrees outside) both thermostats have continuity and the control thermostat also has continuity. With diesel switch on, the burner fires up for about 4 minutes and shuts off. At that point both thermostats still have continuity but the control thermostat does not. Am I correct that the control thermostat is bad and just shutting off the burner before it should? And needs replaced? I truly appreciate all of your help on this issue. Thanks, Dave Link to comment Share on other sites More sharing options...
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