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AquaHot & Front HVAC Vents

Rusty H
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Ours blows hot out of the dash vents with key OFF and furnace running Selector does not matter since there's no vacuum, fan and dash temp dials don't matter, they have no power.  With ignition ON,, there is a relay that switches back to dash controls. Few years difference so the logic could be different.

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I’m assuming you are referring to the dash vents that are supplying AC/heat from the main engine….

No heat from my dash vents with AH on, only place I get heat from AH is through the remote heat exchangers, one under the dash storage drawer between the pilot-co pilot chairs, one under the J couch, one under the toe kick in the kitchen, one in the head, one in the shower room under the sink and one in the rear bedroom.

2005 Dynasty Platnum IV 40’

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No heat from dash vents on our 08 Dynasty. Do you have your AH on Diesel? At 35f the electric elements will not provide enough heat. On our MH there is a switch to turn the AH heat under the radio to a hi speed. Are you parked or driving? Our unit can be kept at 70 degrees even in 15f temp while parked..

Edited by birdshill123
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  • Tom Cherry changed the title to AquaHot & Front HVAC Vents
16 hours ago, Rusty H said:

Should my AH blow out my dash vents.  My friends HRambler does with key off, furnace on, selector on vent , heat selector on hi, fan on hi.  05 Dynasty. Only one AH vent under radio, 35 this weekend  60 in dash area AH on 72. Thanks


Your question, so I understand it, might need a little clarification.  Now this IS MONACO…so follow my logic.

EDIT. Never assume that Monaco did anything for all MH nor did not make any changes.  In a subsequent posts there are instances where the AH was integrated into the HVAC front system.  The explanation below is for my Camelot and not applicable to all models....but the lower end units PROBABLY work this way....  There is a schematic by TrailMug that answers the question.....

Your Front HVAC unit is considered as the “dash” system. If you look on page 390 in your manual, there is a description of the controls.  To the best of my knowledge and understanding, there is NO CONNECTION OR DUCTING between the AquaHot (AH) & the front HVAC system.  They are totally independent.  What you were told may have been an observation of the various “vents” and a misclassification of an AH vent.  Look at page 390 and do the following.

turn on the engine, as sometimes the low battery light will give a false alarm.  Run through the modes with the fan on high.  The main Front vents are on the dash.  There is also, and mine is only on the driver’s side, a floor outlet.  Once you feel the air, you can then identify the outlets. There may be a vent or louver with a sliding control to regulate or turn down the floor heater.

There is probably an AH supply in the lower or floor area of the center console.  For that unit to blow air, the AH must be set in the furnaces- Zone 1 or front.  The fan(s?) for that unit is controlled by the AH unit.  It is a single speed fan.  Memory is a little sketchy as to when the fan comes on….but it may come on first and then the air gets hotter as the boiler temperature reaches 180 DF and the antifreeze or the AH liquid is heated.  

The confusion may be that there are two separate outlets or supplies in the lower and foot side.  One is the front HVAC and the other is the AH.  AGAIN, This is MONACO.  IF Monaco ran the hose for the front HVAC in and through or under the console, that may be coming out of the same supply as the AH, BUT the two systems are not electronically connected, just were in the same area.

Second thing, for your edification, is to UNDERSTAND the modes of the front HVAC.  The air conditioning compressor, which can reduce your fuel economy by 10% is ON in the following modes.

MAX AC; AC; BILEVEL: MIX; DEFROST.  The Compressor is OFF In VENT & FLOOR.  The BILEVEL cools the air, but is basically the same as the AC mode.

It is suggested that you visit this topic as it goes into some details on the AH as well….


There have also been two topics on winter driving and protection.  One of them included the trick of turning the front HVAC temperature to max heat and then setting the mode to MAX AC.  That turns off the compressor and shuts off the incoming air so you get much better heating.

Hope this explanation makes sense.

The Air Conditioner or heat controls may have an error in which modes or settings that the compressor is on.  With switch OFF and fan on high, run through each mode.  MOST Monaco systems have a center off and 

Edited by Tom Cherry
Clarification of Model Specific Function(s)
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22 minutes ago, Doug J said:

On my 03 Navigator all dash vents work with AQH on (either Electric or Diesel) Blower set to high, heat switch off, key off.

Well, looks like we are narrowing down the year they discontinued this feature!

Just need an '04 model yr owner to chime in.

Edited by 96 EVO
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8 minutes ago, trailmug said:

Our Sig has a second heat exchanger in the dash air vent system for AH, and a pair of boiler lines for it visible on the generator firewall. I'd check the plumbing. 👍

WOW....you learn something new every day.  I stand corrected.  FOR MY CAMEELOT, there is NO connection.  In addition, the front radiator is located UNDER the lower drawer of the Console.  I have a VENT (HVAC) there which is fed via the black hose manifold that feeds the upper round vents.  SO, when you turn on the AC, if it is in the floor setting, you get air down there.  But it comes out the side.  

BUT, if the AH is blowing, the air (heated) comes out the front vents.  Thus, the volume or area under the lower drawer acts like a plenum.  SO, it is a matter of what is pushing the air and which side it comes out.

Going out on a limb here.  My AH radiator is external to the Front HVAC system, but is located in a common area where the Front Floor Supply is located.

Maybe this common plenum was eliminated due to space and drawer and cabinetry constrains the the Front AH Radiator is in the HVAC air duct system.  The wiring from the AH control board is just 12 VDC so that could run the AH fans, WITHOUT being intergrated with the Front HVAC Blower motor or controls.

Maybe someone can post about the controls for the system and how they work.

Great exchange and learning session...

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  • 2 weeks later...
On 11/14/2022 at 8:56 PM, Rusty H said:

Should my AH blow out my dash vents.  My friends HRambler does with key off, furnace on, selector on vent , heat selector on hi, fan on hi.  05 Dynasty. Only one AH vent under radio, 35 this weekend  60 in dash area AH on 72. Thanks

Rusty, yes with the Aquahot, the only dash heat will be one vent under the radio.  On my coach, I discovered huge air leaks under the dash where the plywood dash meets the front cap up there the wipers are located (my fingers could fit through the gap) and where the wiring harness comes up through the floor to the left of the drivers seat.  Once these huge air leaks were filled with spray foam, the cold dash area was fixed.  In really cold weather, turn on all your ceiling vent fans and you will find every air leak.  Sealing all of them will make a huge difference in heating and air conditioning your coach.

One more tip - in really cold weather always keep the inside step well cover closed especially at night.

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