If the display function does not work, replace the meter unit.

Check 3-6: Neutral Indicator Light (LED) Inspection
Meter Unit Circuit (ZX1000J Model)Relay Circuit Inspection
Remove the relay box (see Relay Box Removal).
Check conductivity of the following numbered terminals
by connecting the hand tester and one 12 V battery to the
relay box as shown in the figure (see Relay Box Internal
Circuit in this section).
If the tester does not read as specified, re ...
KIBS Servicing Precautions
There are a number of important precautions that should
be followed servicing the KIBS.
This KIBS is designed to be used with a 12 V sealed battery
as its power source. Do not use any other battery
except for a 12 V sealed battery as a power source.
Do not reverse the battery cable connec ...
Storage of Removed Parts
After all the parts including subassembly parts have been
cleaned, store the parts in a clean area. Put a clean cloth
or plastic sheet over the parts to protect from any foreign
materials that may collect before re-assembly.
Inspection
Reuse of worn or damaged parts may lead to serious acci ...