There must be a link
between High Voltage
terminals 1 & 6 and high
voltage terminals 3 & 6.
Make sure both links are
present
MAF STAT CONNECTED NOT CALLING FOR HEAT (BOILER NOT FIRING) WHEN MAF STAT ON MAXIMUM
NO
YES
YES
NO
NO
YES
YES
YES
NO
YES
NO
NO
NO
NO
YES
YES
NO
Is there 230 ~ 250VAC across High Voltage terminals 2 & 4?
Is there 230 ~ 250VAC across High Voltage terminals 1 & 2?
Measure DC voltage (5.1V DC Max.) across
Low Voltage
terminals
3 & 4
Is measured voltage greater
than 4.7V
Is measured resistance
greater than 11K?
Is measured voltage greater
than 4.7V
Check pipe sensor and
connections. If sound, isolate
from mains & measure
resistance across plug J2
pins 5 & 6
Is measured voltage greater than 4.19V?
Is there an external clock
fitted?
Measure DC voltage (5.1V DC
Max.) across
Low Voltage
terminals 5 & 6
Check black wire of MAF stat
goes to
Low Voltage
terminal 3
and red wire of MAF stat goes to
low voltage terminal 4. Ensure all
connections are sound
Check clock is on & measure
output
Check for live supply into clock.
Replace clock if live is present
Is 230 ~ 250VAC present?
Check harness
connections to PCB. If all
OK Replace PCB
Remove MAF stat
connections and link
Low
Voltage
terminals TPV & 3. Is
there 230 ~ 250VAC across
High Voltage terminals 2 & 4?
Open circuit between
clock out & High Voltage
terminal block 1
Unit mains
supply is
missing.
Check spur
e.g. fuse is
intact
Check
connections
to high
voltage
terminals
2 & 3
Problem with switched live output going from High Voltage
terminal 3 to switch live of boiler
Is there 230 ~ 250VAC across High Voltage terminals 2 & 3?
FIGURE 6. HEAT EXCHANGER REMOVAL
11
Sales/Spares & Replacement Help Line 01604 762881
17. FAULT FINDING
16.5 HEAT EXCHANGER REMOVAL
CAUTION: THE ELEMENTS OF THE HEAT EXCHANGER
ARE VERY FRAGILE.
16.5.1 Close the isolation valves and drain down the unit.
16.5.2 Release the clip and the temperature sensor, remove the
heat exchanger and its associated pipework from the unit.
16.5.3 Reassemble or replace in reverse order. Ensure all air
locks are expelled, and check for water soundness.
16.6 AIR FILTER REMOVAL
16.6.1 The air filter is removed by sliding it out from the front of the unit.
CLIP
SENSOR
