The unit does not receive the heart rate signal.
Check if the unit is in the sleep state (power saving feature is on).
Push any button other than the AC button.
Is the heart rate sensor placed in the correct position?
Adjust the position according to the instruction.
Is the heart rate sensor attached securely to your body?
Attach the sensor so that the electrode area contacts closely with your skin.
Is your skin dry (especially in winter)?
Lightly moisturize the electrode area.
Has the battery in the heart rate sensor worn out?
Replace it with a new one (CR2032).
Has the battery in the main unit worn out?
Replace it with a new one (CR2032).
Have the electrodes belts deteriorated over normal use?
Replace them with new ones. (See your local dealer or www.cateye.com.)
The heart rate display occasionally reads zero.
Is the heart rate sensor in correct position?
Adjust the position according to the instruction.
The heart rate reads zero where there is some interference from an outside signal or the transmitter is too far from the main unit. Move closer to the main unit or move away from the radio frequency interference.
The battery in the main unit has worn out. Replace it with a new one.
The display does not show Memory Record file.
Is 
icon on? Is the elapsed time TM measuring?
The display does not show the Memory Record file when the memory record feature is on or elapsed time is running. (See page 19, "Check Memory Record Files")
You cannot turn record memory feature on. ( 
icon does not appear.)
Reset Elapsed Time TM. (See page 20, "Setting up Memory Record")
You cannot change the Interval Timer of memory record.
Is 
icon on?
If memory record feature is on, you cannot change Interval Timer. (See page 19, "Memory Record Interval Selection")
The unit cannot record LAP data.
At least 5 seconds of interval is needed to record the next lap data.
The unit cannot read out LAP data.
Is the elapsed time measuring?
The unit cannot read out LAP data when the elapsed time is measuring. (See page 15, "Lap Data Read Out")
Clock setting screen does not appear.
The display does not show clock setting screen when the elapsed time is running. (See page 13, "Setting Clock Time")