Skip to content
English
More support
Go to fleetwatch.com
  • There are no suggestions because the search field is empty.

What does the green LED on the SRF control box indicate?

understanding the green LED status

Fleetwatch FMS · Fuel Lane Hardware
What Does the Green LED on the SRF Control Box Mean?
The SRF control box (the “black box” in the RIH junction box) has a green VEHICLE PRESENT LED. It shows whether the overhead SRF55 sensor sees a vehicle, and whether the control box can communicate with the sensor.

Reading the LED

Green LED What it means
Off Normal  No vehicle is under the sensor.
Solid Normal  A vehicle is properly parked under the sensor, with its roof directly below it.
Flashing steadily, no bus in the lane Problem  The control box can’t detect the overhead sensor. Most likely a poor connection at the overhead sensor or a failed sensor.
SRF55 internal wiring diagram showing the overhead sensor wired to the SRF control box in the RIH junction box, with the green Vehicle Present LED marked by an arrow
The SRF control box in the RIH junction box. The green arrow points to the Vehicle Present LED. The overhead sensor connects with three wires: ground (black), power (red), and signal (white).

RIH Resetting While Fueling?

If the sensor loses sight of the bus, the RIH may reset several times while a bus is being fueled. The usual cause is the bus’s position.

Roof, not windshield
The sensor works best when the bus’s roof is directly under it. It may not work reliably if the windshield is under the sensor.

To fix it: realign the bus so its roof is under the sensor, then try fueling again. A solid green LED confirms the bus is in the right spot.

Fleetwatch parking diagram: park the vehicle under the SRF55 vehicle detector during servicing to avoid an unintentional reset
Park the vehicle under the SRF55 during servicing to avoid an unintentional reset.

LED Flashing with No Bus in the Lane?

The control box can’t detect the overhead sensor. Check:

1 The connection at the overhead sensor. Make sure all three wires (black, red, and white) are secure at the sensor and at the control box terminals.
2 The sensor itself. If the connections are good and the LED keeps flashing, the overhead sensor may have failed and need replacing.
For step-by-step troubleshooting, including a power cycle with CB1 and a bus test, see Checking the SRF55 Vehicle Detector.
Questions about the SRF vehicle detector? Contact Fleetwatch Support.