40 | P a g e
Pump constantly running.
Cause: Frost protection active or pump PWM fault. Sometimes linked with 109 & 140 fault codes, if so PWM fault.
1. If a frost symbol is present in the boiler display, follow from point 2. If there is no frost symbol on the
display, follow from point 3.
2. Press OK to access the user menu.
a. Select Complete menu and then CH settings.
b. Scroll to Pump continuous running.
c. If Enabled is highlighted, frost protection can be turned off by selecting Disabled.
d. If this function is already Disabled, or the frost symbol still appears after selecting Disabled, check
the flow temperature of the boiler via parameter 8.3.1. If the temperature is less than 8 °C, then the
internal frost protection is active.
i. Confirm the resistance of the T1 flow sensor as per the table on page 67 and replace as
required.
ii. Confirm the wiring harness continuity and contacts are ok. Replace if required.
iii. If the above checks are OK, replace the PCB.
3. Check the PWM signal to the pump is ok by completing the following:
a. Safely isolate the boiler and remove the PWM cable from the pump. Check the 3 pins are not bent –
if bent use a small screwdriver to straighten.
b. Check pump position in relation to the PCB casing. If this is too close it can put pressure on the
PWM connector causing a loose connection. This is usually diagnosed by bring the PCB housing
down towards you and the pump may stop. – adjust the pump position if required.
c. Check the pump PWM via the 3-wire cable connection to the pump on PCB connector CN9 pin 1&2:
1. with the pump off the voltage is +/- 5VDC.
2. 39% load the voltage is +/- 3VDC.
3. 61% load the voltage is +/- 1.9VDC.
4. 100% load the voltage is +/- 0.24VDC.
d. If the voltages are incorrect, replace the PCB.
e. If the voltages are correct, replace the pump.
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