Journey with Confidence RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Take a Speed Test Free 7 Day Trial ×
RV Trip Planning Discussions

Go Back   iRV2 Forums > MOTORHOME FORUMS > Class A Motorhome Discussions
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 03-14-2020, 05:21 AM   #1
Senior Member
CountryB's Avatar
Monaco Owners Club
Join Date: Aug 2017
Location: Orlando, Florida
Posts: 5,819
AquaHot circulation pump pulsing when Off - caused by Big Boy solenoid

I wanted to share this with the forum in case anyone else has this issue.

I have the AquaHot AHE100-04S unit. While walking around the Coach one day I heard a faint "motor pulsing" noise. I tracked it down to the #2 Circulating pump on the AquaHot. The AquaHot was not in use.

The #2 pump makes a pulsing noise (doesn't actually rotate more than a degree) and I can see the pump vanes turn back and forth slightly. Somehow there is a power getting to the pump when the unit is off. The LED light for Pump 2 on the control board also shows a dim flash/blink that matches the pulsing motor.

On the RV Hyrdronic Heater Repair forum, this same issue was posted. The poster "geneo57" figured out what is going on and came up with a fix.
RV Hydronic Heater Forum

The cause is that the Big Boy battery isolation solenoid is sending a DC pulse (it uses a low volatage pulse to keep the solenoid engaged) through the electrical system and that pulse is causing the AquaHot pump to pulse. I don't know if there is a problem with the Big Boy (works fine as far as I can tell) or if the problem is with the AquaHot (overly sensitive control board or failed capacitor on the board, or nothing wrong with AH).

The fix is to add a Capacitor across the Pos. and Neg. terminals that feed the control board. That filters out the stray pulse from Big Boy and stops the pump from pulsing.

The Capacitor is a 2200uF 35V

Just wanted to share this.
P.S. perhaps this Big Boy generated "pulse" is causing other problems with other electronic systems on the coach. But I have not noticed anything else acting strange. i considered adding the cap across the Big Boy terminals to remove the noise at the source, but in the end just did the fix as Geneo57 described it.
Attached Thumbnails
Click image for larger version

Name:	AquaHot _capacitor added to stop circulation pump pulsing.jpg
Views:	16
Size:	91.5 KB
ID:	277960  
Mike --- 2005 Beaver Patriot Thunder CAT C13 525HP --Links below to my OneDrive docs---
*SMC, Beaver, Monaco History, Problems!AtvAXw_lfqbToxXYREK9YdBP08Jn
*Monaco Wiring Diagrams!AtvAXw_lfqbTm0WTuuNqpn9a8hCh
CountryB 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 03-14-2020, 10:14 AM   #2
Registered User
Monaco Owners Club
Join Date: Mar 2018
Location: Blairsville, GA & WPB, FL
Posts: 3,993
Send a message via ICQ to Ivylog
Or a diode on the BIRD is bad?
Ivylog is offline   Reply With Quote


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
On-off on off on off off off rear view camera Bahcml Newmar Owner's Forum 5 08-12-2019 10:44 PM
Is Big boy solenoid supposed to hum? CountryB Class A Motorhome Discussions 36 11-26-2018 01:03 PM
Big Boy Solenoid Janet and Todd Alpine Coach Owner's Forum 33 10-15-2018 09:23 PM
Chassis batteries big boy solenoid issue Nasdaqsam Monaco Owner's Forum 2 08-31-2017 04:55 PM
AquaHot Circulation Problem K7JV Monaco Owner's Forum 6 03-16-2015 10:09 PM

» Featured Campgrounds

Reviews provided by

All times are GMT -6. The time now is 10:09 PM.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2022, vBulletin Solutions, Inc.