CapnDean Posted March 31, 2023 Share Posted March 31, 2023 Outside air temp 70 degrees. Coach is set to electric water heat NOT diesel. Nobody using hot water - no heat requested by furnace - not set for engine preheat... And the AH blower cranks up and the diesel heat fires up for a few minutes.... Just like I need hot water.... but I dont. I have no water leak or anything,.... anybody? Link to comment Share on other sites More sharing options...
timaz996 Posted March 31, 2023 Share Posted March 31, 2023 A difference in temperature between your diesel and electric high temperature thermostat or your electric element is not working. 1 Link to comment Share on other sites More sharing options...
Jdw12345 Posted March 31, 2023 Share Posted March 31, 2023 What model of AH do you have? Link to comment Share on other sites More sharing options...
SteveC Posted March 31, 2023 Share Posted March 31, 2023 4 hours ago, Tim-AZ said: A difference in temperature between your diesel and electric high temperature thermostat or your electric element is not working. Tim is correct. There is one more remote possibility. The diesel and electrical side of the AquaHot are controlled by two different 'control thermostats'. The diesel is marked 190 (operates 175-200) and the electric is marked 198 (185-210). This means that if there is little to no load on the AH system the electrical element will take care of things and the diesel will not kick on. IF the wires have been switched, your AH temp may be controlled by the diesel control thermostat (rather than the electrical control thermostat). Like I said, this is a remote possibility. I would lean more toward the electrical side not functioning correctly. Link to comment Share on other sites More sharing options...
vito.a Posted March 31, 2023 Share Posted March 31, 2023 I've just overhauled our Aqua Hot and learned a lot about the system. I'm not sure how your diesel burned can come on without being selected inside the coach. The diesel burner system runs on 12V DC and the electric heating element runs on 120V AC. I assume with a 2008 model you have the Intellitec multiplex system. It is applying power to the relays to turn on/off the systems you select. I would watch your Aqua Hot system closely to see if there are any more anomalies. Link to comment Share on other sites More sharing options...
Dr4Film Posted April 1, 2023 Share Posted April 1, 2023 The diesel Webasto SHOULD not come on with the diesel switch set to OFF. Someone has messed with your Aqua-Hot. Depending on your model, there maybe four thermostats, two for the diesel and two for the electric assist. OR you may only have one set that controls both the diesel and the electric simultaneously if you have one of the "Baby" Aqua-Hot models. Link to comment Share on other sites More sharing options...
CapnDean Posted April 1, 2023 Author Share Posted April 1, 2023 I have the 450d Link to comment Share on other sites More sharing options...
Dr4Film Posted April 1, 2023 Share Posted April 1, 2023 That is the "baby" model with a 5-gallon boiler tank. The controls for that model are different than the larger boiler tank models. Download your operator's manual and read through it thoroughly to completely understand how it operates. Download the parts and service manual also while you are there. Link to comment Share on other sites More sharing options...
Solution radioman Posted April 1, 2023 Solution Share Posted April 1, 2023 Im guessing if its a 450D you have the electronic LED control board mounted on the bay wall? If this is the case there is only one thermostat that calls for heat. The other two are safety thermos that trip off and turn off the electric element and the second one turns of the diesel if anything goes wrong, they are manual resettable. The one control thermo turns on diesel and electric when the boiler solution drops below a certain temp like 165F. If you dont want diesel to fire up you have to turn off the diesel switch. Link to comment Share on other sites More sharing options...
96 EVO Posted April 1, 2023 Share Posted April 1, 2023 (edited) Burner shouldn't fire if you have the Diesel switch turned off! Otherwise, on your model (same as mine), if you have both diesel & electric switches turned on, the burner will run occasionaly to keep the boiler fluid up to temperature. The diesel and electric side share the same set of thermostat's, so, they will both start simultaneously. Edited April 1, 2023 by 96 EVO Link to comment Share on other sites More sharing options...
radioman Posted April 1, 2023 Share Posted April 1, 2023 Thats what I told him.If you don't want the diesel to run turn the diesel switch off. 1 Link to comment Share on other sites More sharing options...
Tom Cherry Posted April 1, 2023 Share Posted April 1, 2023 1 hour ago, radioman said: Thats what I told him.If you don't want the diesel to run turn the diesel switch off. He stated in the ORIGINAL post that the Diesel was OFF……Set to Electric. Yes, I have the same system. There is a SINGLE Thermostat…..with the high level Safety OF. That thermostat is feeding TWO circuits. When it closes, if the. AH Diesel switch is on, you get fire and fumes. If the AH Electric is on, you get resistance heating. If BOTH, you get BOTH. @96 EVO & @radioman are correct. There is not a separate DIESEL & ELECTRIC thermostat. HOWEVER…. THERE is a confusing line in the post. “AH BLOWER STARTS UP”. I’m interpreting that as one of the AH ZONES is calling for HEAT…..UNLESS, he meant he heard the AH “blower” fan in the outside unit come on. IF there’s an interior Zone AH fan blowing, then there could be a HVAC issue and one HVAC zone was erroneously set on FURNACE. BUT, that’s not going to explain how the 12 VDC signal got from the “OFF” Diesel switch to allow the burner to fire to satisfy the errant HVAC signal. MY ADVICE. Do a HVAC reset (thermostat OFF, Hold Mode & Zone buttons. Turn on Thermostat. FF in display. Verify no zone inadvertently set to HEAT. Go to AH and do a system reset with a paper clip or a skinny dowel. MONITOR & see if it comes back. If so, call AH…. In that case, sounds like a bad board, but they will advise how to troubleshoot…. Link to comment Share on other sites More sharing options...
timaz996 Posted April 1, 2023 Share Posted April 1, 2023 On the money Tom Link to comment Share on other sites More sharing options...
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