Free 7 Day Trial RV GPS App RV Trip Planner Campground Reviews RV Maintenance Free 7 Day Trial ×
RV Trip Planning Discussions

Go Back   iRV2 Forums > THE OWNER'S CORNER FORUMS > Monaco Owner's Forum
Click Here to Login
Join iRV2 Today

Mission Statement: Supporting thoughtful exchange of knowledge, values and experience among RV enthusiasts.
  This discussion is proudly sponsored by:
Please support our sponsors and let them know you heard about their products on iRV2
Thread Tools Search this Thread Display Modes
Old 10-24-2021, 03:07 PM   #1
Junior Member
Monaco Owners Club
Join Date: Aug 2013
Posts: 12
Aqua Hot diesel not igniting

2004 Monaco Windsor with Aqua Hot AHE-100-03S (serial number 03-1168). Prior experience with Aqua Hot in 2007 Monaco Dynasty but always had vendor perform annual maintenance and never had any issues. Purchased current coach Jan 2021 and Aqua Hot was vendor serviced locally Feb 2021. After I picked up the coach from the vendor, Aqua Hot would not run on diesel or electric. Although expansion bottle showed fluid slightly above cold level, determined that fluid level at cap was almost 2 quarts low – coolant sensor doing it’s job! Replaced cap and obtained diluted boiler fluid from vendor (along with an apology).

The system operated flawlessly thru the winter months but has not been exercised since returning from Ruidoso in late-August. Today (ambient 83 degrees and overnight of 65 degrees), there is no ignition on diesel but electric appears to operate correctly. With thermostats OFF, I activated electric switch (diesel switch OFF) and had hot water within 45 minutes. Expansion tank rose to mid-way between hot and cold.

With full tank of diesel, hooked up to 50 amp shore power, 13+ on coach/chassis batteries, and coolant level at cap (determined on a cold unit), turned on diesel switch & light illuminates. Cold air flow at tailpipe and normal high pitched whine at unit. All lights on display are correct. Less than 3 minutes later, system shuts down. Since this is my “project coach”, I decided I would get bold and see if I could handle this issue all by my lonesome. Any initial assumptions that I should concentrate on?

Ordered and received parts for annual maintenance and started reading everything I could find on this model of Aqua Hot. Two different fuel filters apply to this model – one with a water separator and one without. Coach currently has the fuel filter/water separator style installed so that is what I will keep going with and will obtain a spare to carry in the coach unless y’all convince me that the larger filter without a water separator is the way to go. Of course, I got the wrong filter initially. BTW, the fuel filter is installed above the level of the tank – OK or should it be lower?

Noted that the AHE-100-03S is “a major redesign of the AHE-100-02S model” and is visually similar in layout to the AHE-100-04S. Service and Installation Manuals do not appear to exist for the AHE-100-03S but have obtained the Owner and Parts Manuals. Obtained Service and Installation manuals for the AHE-100-04S. Does it appear that I have the right reference materials?

Noted that full strength coolant will plug check valves so purchased a fractometer -- it shows 44%. Sound OK or should coolant be further diluted to 50%?

I will proceed with the annual maintenance when my bad leg lets me get down low enough to work on the unit without screaming. Anything else besides change fuel filter, change nozzle, clean burner and photo disk, and check for water and/or air in fuel line?

Thanks and safe travels!
ccdriver99 is offline   Reply With Quote
Join the #1 RV Forum Today - It's Totally Free! RV Community - Are you about to start a new improvement on your RV or need some help with some maintenance? Do you need advice on what products to buy? Or maybe you can give others some advice? No matter where you fit in you'll find that iRV2 is a great community to join. Best of all it's totally FREE!

You are currently viewing our boards as a guest so you have limited access to our community. Please take the time to register and you will gain a lot of great new features including; the ability to participate in discussions, network with other RV owners, see fewer ads, upload photographs, create an RV blog, send private messages and so much, much more!

Old 10-24-2021, 04:46 PM   #2
Senior Member
vito.a's Avatar
Monaco Owners Club
Join Date: Oct 2009
Location: Tucson, AZ
Posts: 5,476
We have the same Aqua Hot unit. They are great appliances.
Not igniting: First confirm fuel flow. Then possibilities are high limit thermostat, Fuse, E or F, igniter electrodes, ignition coil, or main controller.

I usually use the AHE 100-02S manuals.

Diesel-Burner’s Combustion
Process does not take place.
Loose Harness Plug Connections at the Control Unit.
Open “E” or “F” Fuse at the Aqua-Hot.
No Fuel to the Diesel-Burner.
Defective Fuel Nozzle.
Check Harness Plug Connections to be secure and in
place on the underside of the Control Unit.
Replace “E” or “F” Fuse.
Check Fuel Filter and Fuel System.
Replace Fuel Nozzle.

Diesel-Burner’s Combustion
Process stops after 30 sec.
Loose Harness Plug Connections at the Control Unit.
Less than 10 Volts DC to the Aqua-Hot.
Check Harness Plug Connections to be secure and in
place on the underside of the Control Unit.
Check House Batteries and Charging System.
Attached Files
File Type: pdf Aqua Hot AHE-100-02S Owners Manual 05-02.pdf (303.7 KB, 5 views)
97 Monaco Windsor- Sold
07 Monaco Executive McKinley- Sold
04 Monaco Signature Chateau IV
vito.a is offline   Reply With Quote
Old 10-24-2021, 06:19 PM   #3
Senior Member
96 Wideglide's Avatar
Holiday Rambler Owners Club
Join Date: Aug 2010
Posts: 8,173
Should be a little igniter gap gauge screwed to the side of the burner unit.

With your symptoms, checking the igniter gap is where I would start.
Ben & Sharon
2008 43' Holiday Rambler Scepter PDQ
96 Wideglide is offline   Reply With Quote
Old 10-24-2021, 06:35 PM   #4
Senior Member
96Bounder1st's Avatar
Monaco Owners Club
Fleetwood Owners Club
Join Date: Sep 2016
Location: Manitoba, Canada
Posts: 917
After you have done your listed maintenance also check the low temperature and high temperature DC thermostats on the unit itself for corroded connectors.

I had, 1. A totally sooted up flame sensor and after throwing large amounts of money at it found the spade terminals to all be corroded to uselessness.

After changing the four crimped connectors and using conductive grease all my intermittent troubles ceased to exist.

I did end up with a brand new spare controller, coil, thermostats, AC and DC however and a spare fuel filter, which is mounted above the fuel tank and a nozzle.

The advice given above by previous posters is very good.

I have found occasionally if I try to use the electric and shut off the diesel side without checking if it is running can cause a flooding condition in the combustion chamber that is devilishly hard to clear.

Good luck and keep us advised of what you find.

2002 Monaco Windsor 40PKD. Marjorie 2.
2015 Equinox V6 Roadmaster tow setup
2019 ALP Adventurer 24DS for the short trips. April, 2021
96Bounder1st is offline   Reply With Quote
Old 10-24-2021, 06:52 PM   #5
Senior Member
photopilot's Avatar
Monaco Owners Club
Join Date: Jan 2016
Location: New Hampshire
Posts: 480
X2 on the igniter gage. Mine was missing and I figured not a big deal. Spent hours troubleshooting until I bought a replacement gage. Problem solved.

Walt & Bonnie
2006 Monaco Camelot 40PAQ, Cummins 400 ISL
'16 Ford C-Max, Roadmaster BP, Sterling towbar
photopilot is offline   Reply With Quote
Old 11-11-2021, 09:25 AM   #6
Junior Member
Monaco Owners Club
Join Date: Aug 2013
Posts: 12
Thanks for the replies. My Aquahot is now running like a champ! I changed the fuel filter/water separator and fuel nozzle. The electrodes required a very small amount of tweaking to sit in the gauge properly. The electrodes were moderately carboned and the burner tube was so severely carboned that it would not come out without max effort. Since my leg was complaining and I hesitated to force the burner tube for fear of doing more damage, I decided that it was time for professional help. I made an appointment with an Aquahot Authorized Service Center – Nacogdoches Motorhome Services. I asked if I could watch and learn. Not only did he allow me to watch the entire process, he walked me through each of the steps with a full explanation. Great tech with the right equipment and training! He cleaned and adjusted the electrodes, removed and replaced the bad burner tube (sucker was almost frozen in place due to carbon buildup), thoroughly cleaned the combustion chamber (including exhaust pipe), replaced the nozzle out of an abundance of caution, and adjusted the fuel pressure down from around 165 psi to 135 psi. After getting ignition, he checked all pumps and determined that the zone two pump was toast. Replaced the pump and rechecked all operations. Parts were installed at or below prices that I had checked online and the labor rate was a reasonable $115/hour. Seth Whitehead is the tech and I will definitely be returning should the need arise in the future.
ccdriver99 is offline   Reply With Quote

aqua hot, diesel

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Onan RV QG 4000 Not Igniting smasiello MH-General Discussions & Problems 7 08-30-2017 03:12 AM
Bounder: Water heater not igniting stormy2000 Fleetwood Owner's Forum 3 03-07-2016 07:10 AM
ATWOOD Furnace not igniting coburncliff RV Systems & Appliances 5 03-22-2015 08:49 AM
AquaHot 375LP propane burner not igniting Josh2129 Entegra Owner's Forum 7 12-08-2014 10:18 PM
Water heat not igniting bananabelle RV Systems & Appliances 1 01-16-2012 04:09 AM

» Featured Campgrounds

Reviews provided by

All times are GMT -6. The time now is 03:38 AM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2021, vBulletin Solutions, Inc.