FAULT FINDING & DIAGNOSIS
6 720 815 725 (2015/05)
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7
FAULT FINDING & DIAGNOSIS
7.1
NO HOT WATER ON OPENING A TAP (NEW
INSTALLATION)
When a hot tap is turned on and only cold water is delivered, and the
boiler does not fire up, the first thing to check would be to see if the hot
and cold domestic water pipes are installed the correct way round.
To display the value of the service function:
▶ Press the
button for more than 10 seconds (the display shows
). When the button lights up orange, release it. In the display
appears Digit.Letter e. g. 1.A.
▶ Press the
eco
button for going up (service next) or
button for
going down (service previous) to select service function
6.d
.
▶ Press the
button and release it. After releasing the button will light
up orange. The display shows the current flow rate.
▶ With the hot tap turned on, the current flow rate is displayed in the
digital display. If the hot and cold DHW pipes are reversed then the
display will indicate no flow, and the display will show 0.0.
7.2
FAULT FINDING
The electronic control system for this boiler incorporates a blue central
indicator. This normally confirms the permanent mains supply but, by
flashing during a fault. The seven segment display on the boiler fascia
give an alpha numeric fault code. Use the table below to identify the fault
code and cause.
A more detailed fault finding procedure is described in the Service
Engineer's booklet.
This fault finding system assumes that the appliance has been operating
normally until the time of failure (i.e. not a first installation error).
PRELIMINARY CHECKS:
Preliminary electrical system checks are the
first electrical checks to be carried out during a fault-finding procedure.
On completion of the Service/Fault-Finding task which has required the
breaking and remaking of electrical connections, check: (a) EARTH
CONTINUITY
(b) SHORT CIRCUIT CHECK
(c) POLARITY
(d) RESISTANCE TO EARTH
You can also use this menu item to check the hot water
flow rate, and complete the Benchmark Logbook during
installation. Carry out the sequence described, and
when the pipes are correctly fitted the boiler will display
the actual hot water flow rate in litres per minute.
This fault finding information is for guidance only.
Worcester, Bosch Group cannot be held responsible for
costs incurred by persons not deemed to be competent.
Display code
Description
Remedy
A1
Pump has run dry or pump has stalled/seized.
Check for water leaks.
Free the pump or replace.
A7
Hot water NTC sensor defective.
Check:
- hot water NTC sensor
- connecting lead for circuit breaks/short circuits.
A8
Break in communication to FX/Sense controls.
Check electrical connections.
b1
Code plug not detected.
Insert code plug correctly, test and replace if necessary.
C6
Fan speed too low.
Check:
fan lead and connector, and fan; replace as necessary.
E2
CH flow NTC sensor defective.
Check CH flow NTC sensor and connecting lead.
E9
Safety temp. limiter in CH flow has tripped.
Check:
- system pressure,
- safety temp. limiters,
- pump operation,
- fuse on pcb, bleed appliance.
EA
Flame not detected.
Is gas cock turned on?
Check:
- gas supply pressure,
- power supply,
- igniter electrode and lead,
- ionisation sensing electrode and lead,
- flue duct and CO2 level.
F0
Internal error.
Check electrical connector contacts, programmer interface module
ignition leads are not loose; replace pcb if necessary.
F7
Flame detected even though appliance switched off.
Check:
- electrode assembly,
- dry pcb.
- Flue clear?
FA
Flame detected after gas shut off.
Check:
- gas valve; resistance, coil 1 = 190
, coil 2 = 390
- wiring to gas valve.
Clean condensation trap and check electrode assembly.
Flue clear?
Fd
Reset button pressed by mistake.
Press reset button again.
Table 15
