Page. 18 of 29
March 2016
Edition 1
PLANAR
Check the sensor for open circuit with a tester. If there is an open circuit fault, the
sensor is defective.
Check insulation resistance between the terminals and the housing. The resistance
should be not less than 100 MOhm at 100V.Ambient temperature during resistance
measurements must be between 15 and 35°C, relative humidity less than 80%. If insulation
resistance does not meet this requirement sensor should be replaced.
Check the sensor terminal on the control unit. Install a jumper instead of the sensor
(Figure 9). If the heater starts with no fault code, the CU is OK. Turn off the heater and
remove the jumper.
If an error occurs during operation of the heater, it is possible that there is a crack
(open circuit fault) in the junction of the thermocouple sensor. There are two methods to
identify the problem:
1. Disconnect sensor from control unit, connect sensor wires to the multimeter (to
terminals of temperature measurement) and heat the sensor with heat gun or lighter. The
temperature rise should be smooth. If the temperature changes suddenly, or it shows the
initial value, the sensor is damaged. In this case, after cooling, the open circuit fault may
disappear.
2. Disconnect the sensor from the heater, and measure the voltage generated by the
sensor when heated. When the sensor is heated to +100°C (temperature of boiling water),
the voltage should be approximately 3 millivolts. The voltage on the terminal marked
with red, should be of positive polarity relative to the terminal marked with black.
Check the polarity of the sensor connection to the CU (wire with black marking is
connected to the connector terminal of the CU with a black dot). A magnet can be used to
check the correctness of marking. Contact of the wire with the black mark is magnetic. If
necessary, swap the terminals in the sensor connector of the control unit.
In the case of an open circuit fault, sensor is defective and should be replaced.
To check the sensor terminal in the CU, install a jumper instead of the sensor (Fig.9).
- If the heater is started and there is no sensor fault, the CU is OK. Remove the
jumper and connect a working sensor.
- If the problem persists, replace the CU.
Fig. 9 – Jumper
Fig. 9а – Connection
Remove dirt and oil from the contacts with a clean cloth soaked in degreaser.
