Unstirred water bath SAP, JBA, JBN Service Manual (Version 1.0) September 2013
31667 Page 12 of 23
3 Common service tasks
3.1 Resetting the Over-temperature Cut-out
This task is required when the unit displays an diagnostic message.
WARNING: Disconnect the unit from the mains voltage supply by unplugging the mains
cord before dismantling the unit
Remove the base plate of the bath - See section 2.3.1
Inspect the mat for any sign of blistering, discolouring or other damage due to excessive
temperatures – if the mat is damaged it must be replaced.
If the mat is undamaged, locate the cut-out device fitted to the heater mat. See photo below.
Note, the 34 litre bath has 3 separate cut-out devices.
Depress the actuator in the centre of the device. There will be an audible click as this is
relocated.
If there is no click, then the cut-out has not activated. Inspect the heater mat and wiring for
faults.
Refit the base plate.
Refill the bath and connect the mains lead.
Switch on the bath and check the water temperature is displayed as expected.
If the display continues to show OTC then there is a fault in the heater circuit. Check the
electrical continuity of the heater mat. Typical resistance values are given in Section 4.2.2.
Over-temperature cut-out device
3.2 Replacing a tank, heater and probe assembly
This is required if the tank is damaged or the mat or probe are faulty
WARNING: Disconnect the unit from the mains voltage supply by unplugging the mains
cord before dismantling the unit
Dismantle the unit following instructions in Section 2.3 as far as removing the tank
Remove the drain fittings from the tank
Refit the drain fittings to the new tank ensuring that the O-ring is correctly seated
Fit a replacement tank, heater and probe assembly and re-assemble following the instructions
in section 4.2
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