ARP Fridge Defend - Sht Boiler Sensor; LO Boiler Sensor Reading; O*F*8; H*O*8

ARP Control v5.x Troubleshooting Guide 0 © 2013-2020 ARPC L.L.C. All rights reserved. 11 04/20/202
the RTD Table at the end of this document
for reference.
b) RTD wires from control to the sensor are
broken or have a bad connection. A
resistance test from the control to the wire
connections at the RTD should show open or
high resistance in this case. If RTD wire has
become frayed or has an intermittent
connection, moving the wire while observing
the resistance of the wire under test should
show a change of resistivity. Replace any
wires that indicate high resistance.
3.5 SHt Boiler Sensor
If the RTD sensor is shorted, SHt will be
flashed out. See 2.9 SHt for further info.
User should disconnect the sensor and
check its resistance value by using the table
at the end of this document. If the resistance
substantially differs from the table, the
sensor has failed. Please contact ARP
Control for a new RTD. Also see RTD
TROUBLESHOOTING and perform these
tests.
3.6 -LO Boiler Sensor Reading
The ARP boiler temperature sensor is
measuring a value lower than 0°C (32°F).
3.7 *O*F*8
Depending on the conditions, it will take
about 4-5 hours, and many restart attempts,
before the ARP turns off the system and
warns the operator by displaying *O*F*8 on
the display. At this point the operator must
restart their system by turning off the ARP
after the boiler has cooled. As a rule of
thumb, using caution to avoid being burnt,
one should be able to touch the boiler
housing without burning your hand when the
boiler has cooled to a safe temperature.
DANGER Care must be exercised
during a restart in this situation. It may be
that the refrigeration unit needs maintenance
that is beyond the abilities of the operator. Or,
the cooling unit has failed, and by turning off
the Fridge Defend, the boiler will experience
unsafe runaway temperatures. If the ARP
keeps trigging due to high boiler
temperatures at each successive attempt to
restart the refrigerator, the ammonia in the
system may need to be remixed, or the
cooling unit may have completely failed.
Because one cannot easily remove the
refrigerator and tip it over to mix the fluids
such as described in the burping section 4.5,
the motion of driving may resolve this
situation. The motion of driving helps mix the
fluids and will help cool the boiler thereby mix
the ammonia back into the system fluids. It is
emphasized that you are in charge of
safety, please take your problems to a
qualified service facility if you do not feel
qualified to resolve any issues that may
affect safety.
3.8 *H*O*8
If HO8 is displayed with all of the dots
illuminated, the ARP has turned off the
refrigerator at a very high temperature. It is
important to check the fridge for failure
before attempting to resume operation. The
cooling unit must be allowed to cool to
ambient temperature if this event occurs.
Please seek a qualified RV technician if you
are not qualified to make safe decisions.
See 3.20 ARP Reset Procedure for
additional information.
3.9 OR (OA) Fan Temp Reading
When measuring the fan temperature in the
ARP mode with the center button, if OR (OA)
is displayed the fan sensor is outside of its
normal measurement range, which is from
35F to 155F.
3.10 bAd
If the ARP Control is in the Auto Tune mode,
and the boiler sensor exceeds 250C
(482F), the bAd error will flash. A possible
cause for this message is the ARP boiler
sensor is too close or touching one of the
heat sources, either the electric heaters or
the flue tube. Check the sensor and
reposition before running Auto Tune again.
3.11 F4 or F5 SetUp Button Test
When the control is in the ARP Control mode,
the SetUp button performs tests of the
controller. If during the automatic controller
test F4 or F5 is displayed, contact ARP