Regal LS4C Owner's Manual page 129

If warning Red LED fails to come on & horn fails
to sound, remove display head & return to factory
for repair. Note that due to the harsh environmental
conditions in marine applications, it is recommended
to replace the gasoline fume sensors every 3 to 4
years.
Refer to the equipment manufacturer's manual for
additional operating information along with more
troubleshooting.
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