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AC Relay:
The AC relay is an electrical device where the DC circuit
from the electric switch determines whether the AC power is
permitted to flow to the electric heating element. This al-
lows the 12 VDC electric switch to switch the 120 VAC
electric heating element on and off in conjunction with the
interior switch panel and control thermostat even though the
electric heating element is on a separate circuit.
Troubleshoot the AC relay if the following condition has
occurred:
The electric heating element fails to operate.
Troubleshooting:
1. Disconnect the AC power source to the motorhome
(unplugging from shore power or shutting off the gener-
ator).
2. Turn the electric element switch on the interior switch
panel .
3. Using a voltmeter, check pin AI on the terminal block
for 12 Volts-DC. If no voltage is present:
A. Check the B fuse on fuse block, for power. If no
power is present check fuse.
B. If fuse is good, follow troubleshooting guide for float
switch.
4. Using a Voltmeter check pin A0, on terminal block, for
power.
A.
If no power is present follow troubleshooting
guide for the electric element switch.
B. If 12 Volts of DC power are present, continue:
®
© 2009 Aqua-Hot
375D Hydronic Heating System Service Manual—Rev. A
S
4: A
ECTION
QUA
5. Locate the VAC relay.
A.
Check pins 1 & 0 for 12 VDC power and ground.
1. Pin 1 is - and Pin 0 is +.
If there is no 12VDC + and - present:
1. check wires for damage or loose connec-
tions.
2. Follow the instructions in this manual for
trouble shoot the Electric element Control
thermostat.
F
AILURE TO DISCONNECT ALL POWER SUPPLIES AND
TO ALLOW THE HEATER TO COOL BEFORE SERVICING
COULD CAUSE SERIOUS DAMAGE OR PERSONAL INJURY
B. Ensure that all the A.C. power supplies to the coach
have been disconnected.
1. Turn the electric switch to the on position and
Verify it is sending 12VDC power to the A.C.
relay.
2. Locate the AC wires connected to the AC relay
(pins 4 and 2), and remove the AC wires from
the relay.
3. Using an ohmmeter, check the relay AC pins (4
and 2) for continuity.
If no continuity exists, follow the instructions in this
section to replace the AC relay.
-H
C
OT
OMPONENTS
/
OR
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— Page 38 —
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