ADS Environmental Services IETG FlowHawk QR 775012 A4 - Manual (Page 343)

Maintenance and Troubleshooting 8-59
Problem Individual SURFACEVEL_3 values consistently read -
9.99.
Possible
Causes
Sensor may be faulty.
5-volt fuse on regulator may have blown.
Possible
Solutions
Replace the Surface Combo Sensor.
Replace the 5-volt blue fuse (when replaceable) on the
regulator or return the monitor to IETG for regulator
replacement.
Caution: Do not connect a questionable sensor to
another monitor before verifying the integrity of the
sensor. A shorted sensor will blow the 5-volt (blue)
replacement fuse on the regulator in the monitor.