Cause: The recirculated sensors are only used on machine models of
electronic expanssion valves and the back temperature value is
considered as the basis for adjustment of the electronic expanssion
valve and determination if the four-way valve changes the position
normally during heating. When the main PCB detects open circuit or
short circuit of the recirculated sensor, it would raise an alarm of
"recirculated sensor error" and send it to the Indoor Unit main PCB to
indicate it.
Inspection path: four-way valve →recirculated sensor → sensor wire
→ connectors → Outdoor Unit main PCB
1. If the error appears in heating but not in cooling, first check if the
four-way valve failed to change the position or there is a back flow,
which can be estimated by measuring the high and low pressures with
the pressure meter; for the consideration of electricity control, we can
use a multimeter. During heating, check if the four-way valve terminal
can switch a circuit of 220V, if yes and the four-way valve still is
faulted in the position changing, the four-way valve is faulted; and if
there is no circuit over 220V in heating, it means the Outdoor Unit
main control valve is faulted.
2. If it is not the four-way valve that is faulted, check on the resistance
value and short circuit problems and the resistance value shall be
within a proper range (around 20KΩ at temperature of 25℃).
3. Check whether the terminal connectors are well fixed; check
whether the weld between the terminal and the main PCB is loose, and
pull the terminal slightly for inspection if necessary.
4. Check whether the sensor is affected with damp. For the recirculated
sensor, if the led is on the above and thecopper pipe is below, it is
possible to be damped.
5. The maintenance personnel can replace the possibly faulted
recirculated sensor with a normal one and if the error disappears, it
means the original recirculated sensor is faulated and needs to be
replaced; and if the error is still there, consider to replace the Outdoor
Unit main PCB.
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