Three-Way Valve
Low-Temp Cutoff Thermostat
©Aqua-Hot®
125-DN1 Service Manual
REV 220421
©Aqua-Hot®
125-DN1 Service Manual
REV 220421
p. 25
p. 24
Three-Way Valve
Introduction:
The three-way valve (aka the summer/winter valve) is
responsible for changing the flow of coolant either through the
interior heating zone (int heat) or circulating coolant within the
boiler tank (stir mode) to produce hot water.
If the three-way valve has failed, it can lead to a loss of interior
heat and/or hot water. Follow the steps below to troubleshoot
the three-way valve.
Troubleshooting Procedure:
Continue trouble-
shooting here
Are the hoses warm and
cool during the conditions
described above?
Yes
No
Replace the
three-way
valve
Set the unit to call for
interior heat and perform
the test again.
The hoses which were
previously cold should now
be warm. Are these hoses
now warm?
Replace the
three-way valve
Please contact
Aqua-Hot for addi-
tional assistance
Yes
No
Go back to the Aqua-Hot
LCD screen. Navigate to
the TEST page and tap
NEXT.
Tap THREE-WAY VALVE
to actuate the three way
valve.
Leave the probes of the
multi-meter in place.
Check the multi-meter.
Does the voltage polarity
measured by the meter
invert?
Yes
No
Replace the
three-way
valve
Replace the
controller
Locate the Aqua-Hot LCD
screen. Navigate to the
TESTING page (Figure 47).
Tap NEXT
The 3-way valve should
begin to actuate. This
can be heard outside the
cabinet.
Yes
No
Activate the electric or
diesel burner and allow
the heater to heat to
temperature
Locate the J6 plug and
test for voltage between
pins J6-10 and J6-11
Is voltage present between
these pins?
Yes
No
Continue
trouble-
shooting to
the right.
Replace the
controller.
Tap THREE-WAY VALVE
Does the three-way valve
actuate?
Continue troubleshooting
to the right.
Open a hot water faucet
within the coach.
1.
1.
2.
2.
Figure 47
Continue trouble-
shooting here
Low-Temperature Cutoff Thermostat
Introduction:
The Low-Temperature Cutoff Thermostat (LTCO) is installed
to measure the incoming domestic water temperature. Using
that reading, the Aqua-Hot controller is able to determine
whether a demand for hot water exists or not.
This thermostat should be diagnosed if there is a lack
of interior heat or hot water and the tank is up to operating
temperature. Follow the directions below to diagnose, and if
necessary, replace the Low-Temperature Cutoff Thermostat.
Troubleshooting Procedure:
Use the following troubleshooting tree to diagnose the Low-
Temperature Cutoff Thermostat.
Locate the Aqua-Hot
LCD screen. Navigate to
INPUTS FROM AQUA-HOT.
Turn on a hot water faucet
within the RV. Monitor the
Aqua-Hot LCD.
Does the LTCO element
display “HOT WATER”?
Yes
No
The LTCO is functioning as
intended.
Locate the LTCO at the
unit, and using a multi-
meter, test for continuity
across the thermostat.
Does the LTCO have
continuity while water is
flowing?
Yes
No
Replace the
controller
Replace the
LTCO
Replacing the Low-Temperature Cutoff Thermostat:
1. Disconnect all sources of AC and DC power from the Aqua-
Hot
2. Disconnect the wires from the LTCO.
3. Remove and discard the defunct LTCO thermostat using a
⅝” wrench.
4. Position and secure the new LTCO thermostat into place.
5. Connect wires J4-1 and J4-2 to the new LTCO thermostat.
Low-Temperature Cutoff
Figure 45
Figure 44
Low-Temperature Cutoff
Figure 46
NOTE:
The side panel has been made transparent in the
view above to aid in the explanation of the repair. DO NOT
remove this side panel. Doing so risks irreparable damage
to the Aqua-Hot.
Grab the hoses
highlighted green below.
While hot water is
running they should be
hot to the touch.
Grab the other hoses
highlighted green below.
While hot water is
running, these should
be cool.
