FAULT FINDING & DIAGNOSIS
6 720 803 599 (2012/06)
49
7
FAULT FINDING & DIAGNOSIS
7.1
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 8 716 115 748.
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
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 TD200 or/and RT10.
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
Ω
, coil 2 = 390
Ω
- wiring to gas valve.
Clean condensation trap and check electrode assembly.
Flue clear?
Fd
Reset button pressed by mistake.
Press reset button again.
Table 12