Mikuni MX40 Guide

Does the light on
the
on / off switch flash ?
Check that the
timer thermostat ( If
fitted ) is turned up
No
Yes
No
Heater starts
ignition
cycle ?
Problem solved
Yes
Yes
No
Is the diagnostics
light on the control
box flashing ?
Check that the
12 / 24 V
supply to the
heater is O .K
No
Suspect Control
box
Count the number
of flashes
Yes
Yes
Mikuni MX 40 Troubleshooting flow chart
Heater does not function
3 21 456789

No
Does the water
pump
start ?
Replace control
box
Problem solved Does heater start ?
No
Yes
Yes
Does the air motor
start after approx
40 seconds ?
Does the fuel pump
click ?
Yes
No
Replace 7.5 A fuse
Does the air motor
operate ?
Replace air motor
No
Replace fuel pump
No
Does the fuel pump
click ?
When fuel primes
problem should be
solved
Yes
Yes
Does combustion
start ?
( roar from exhaust )
Yes
Does heater start
but fails after 3
attempts
Check that fuel is
present
No
Does the heater
now start and run ?
Problem solved
Yes
No
Yes
Clean the flame
sensor
( see note )
Does the heater
now
start and run ?
Problem solved
Yes
No
Contact an
authorised
dealer
No
Mikuni MX 40 Troubleshooting flow chart
Control box : '1 ' flash - Indicating 'Ignition failure'

Mikuni MX 40 Troubleshooting flow chart
Control box : '2 ' flashes - Indicating 'flame sensor failure'
Is the wiring loom
all o .k?
Replace wiring
loom
( see note )
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Replace flame
sensor
Contact authorised
dealer
Problem solved
Yes
No
No

Mikuni MX 40 Troubleshooting flow chart
Control box : '3 ' flashes - Indicating ' thermistor failure '
Is the wiring loom
all o .k?
Replace wiring
loom
( see note )
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Replace thermistor
Contact authorised
dealer
Problem solved
Yes
No
No

Mikuni MX 40 Troubleshooting flow chart
Control box : '4 ' flashes - Indicating ' Waterpump failure '
Is the wiring loom
all o .k?
Replace wiring
loom
( see note )
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Replace 3 amp fuse
Bleed radiators
or matrix heaters
Replace water
pump
Yes
No
No
Does the heater
start & cycle
correctly ?
Problem solved
Yes
No
Is the water primed
OK ?
No
Does the heater
start & cycle
correctly ?
Problem solved
Yes
Contact an
authorised
dealer
Yes No

Mikuni MX 40 Troubleshooting flow chart
Control box : '5 ' flashes - Indicating ' Air motor failure '
Is the wiring loom
all o .k?
Replace wiring
loom
( see note )
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Replace the 7.5 A
fuse
Contact authorised
dealer
Replace the air
motor
Yes
No
No
Does the heater
run OK ?
Problem solved
Yes
Does the heater
run correctly ?
Problem solved
No
No
Yes

Mikuni MX 40 Troubleshooting flow chart
Control box : '6 ' flashes - Indicating ' fuel pump failure '
Is the wiring loom
all o .k?
Replace wiring
loom
( see note )
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Replace Control
box
Problem solved
Replace fuel pump
Yes
No
No
Does the heater
operate correctly ?
Contact authorised
dealer
No
Yes

Mikuni MX 40 Troubleshooting flow chart
Control box : '7 ' flashes - Indicating 'glow plug failure'
Is the glow plug
wiring all o .k?
Replace glow plug
wiring loom
( see note )
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Replace glow plug
Problem solved
Replace control
box
Yes
No
No
Does the heater
start ?
Contact authorised
dealer
No

Mikuni MX 40 Troubleshooting flow chart
Control box : '8 ' flashes - Indicating ' High or low voltage '
Is the vehicle / boat
battery charged ?
Charge batteries
No
Does the heater
start ?
Yes
Does the heater
operate ?
Problem solved
Yes
Check supply
cables
to heater
Contact authorised
dealer
Replace control
box
Yes
No
No
Does the heater
now operate ?
No
Problem solved
Yes

Mikuni MX 40 Troubleshooting flow chart
Control box : '9 ' flashes - Indicating ' Overheating failure '
Is the system full
of coolant
Fill system and
bleed
radiators / matrix
heaters
No
Does the heater
now
cycle correctly
Yes
Does the heater
operate ?
Problem solved
Yes
Check for
damaged /
kinked pipes
Contact authorised
dealer
Problem solved
Yes
No
No