IDEAL istor HE260, Installation And Servicing, Page: 67 / 80

67 istor system store -
Installation and Servicing
FAULT FINDING
F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING F
AUL
T FINDING
101 H.....1..... (CONTROL TEMPERATURE SENSOR)
YES
Is there continuity between the PCB
and the thermistor ?
Check resistance. The sensors can be checked by
measuring their resistance, using a suitable multimeter
connected across the sensors' terminal pins
At 25
o
C expect 9,700-10,300 Ohms
At 60
o
C expect 2,400-2,600 Ohms
At 85
o
C expect 1,000-1,100 Ohms
Remove the boiler control
thermistor from the CH
flow pipe and disconnect
thermistor wires.
Are the thermistor values correct ? Replace the thermistor
NO
YES
Replace PCB
Check and replace wiring
as necessary
NO
Does the pump setting give a differential
across the boiler in excess of 25
o
C
Can the overheat condition be reset by pressing
the boiler reset button when the system is cold ?
Replace the system pump
Set CH control knob to maximum.
If the overheat trips again measure the flow temp:
Over 90
o
C Check control thermistor
(
Refer to Frame 68) .
Under 90
o
C Replace overheat 'stat
YES
YES
Check that the pump is rotating freely.
Is differential now below 25
o
C ?
NO
NO
99 L.......A......................... (OVER HEAT SENSOR)
Fill and vent the system and open all
isolation valves
YES
Is the boiler and CH system filled with
water and all isolation valves open ?
OK
NO
YES
NO
Replace overheat thermostat
100 L....8..... (FAN)
Is nominal 330 V DC present across
red and blue at the fan connector as
reset button is pressed?
Replace fan
YES
NO
Replace harness
Replace PCB
YES
Is 14V DC present
across yellow and pink
at the fan connector?
Check wiring harness for
continuity. Is there continuity?
NO
YES
NO
Note.
With V9 Primary Control PCB, overheat LA/HA or H9/L9 when
reset will display 3 horizontal lines and will not attempt to refire
until the temperature in the heat exchanger drops below 50
o
C.