How to Tell if an Automatic Gate Vehicle Loop Is Working

An underground vehicle loop is a wire installed in pavement and connected to a detector. When a vehicle changes the loop’s inductive field, the detector sends a command or safety signal to the gate controller. Different loops may be assigned to free exit, obstruction protection, shadow or other site-specific functions.

Symptoms of a loop problem

• The gate does not open when a vehicle reaches the exit area.
• The gate stays open after the vehicle leaves.
• The gate opens or reverses without a vehicle present.
• The problem appears after rain or pavement work.
• A detector indicator remains constantly active or never changes.

What can be observed safely

• Move every vehicle and metal object away from the loop area.
• Observe the detector indicator from a safe position, if it is visible without touching energized components.
• Drive a normal vehicle into the detection area and note whether the indicator changes.
• Record the gate controller input light at the same time, when safely visible.
• Document rain, standing water, pavement cracking or recent construction.

Safety: Do not jumper a loop input or change sensitivity and frequency settings without knowing the loop’s assigned safety or control function.

Reviewed September 22, 2026. Procedures and diagnostic codes vary by operator model and production generation; use the manual for the exact equipment installed.