Electric Strike Buzzes But No Release After Install Decision Tree

Why this matters

You installed an electric strike, it buzzes or clicks on a valid credential, but the door does not release. A buzzing strike that holds is a strike that is partly energized and partly defeated, and the cause is almost always electrical undersupply, mechanical preload, or a fail-mode and AC/DC mismatch. This is a high-stakes diagnosis: a strike that intermittently fails to release on a fire-rated or egress opening is a life-safety and code problem, not just an annoyance. The buzz tells you current is flowing, which rules out a dead circuit and points you at four specific causes: insufficient voltage at the strike, the wrong AC-versus-DC variant, latch preload jamming the keeper, and a strike fighting its own fail-secure mechanism. Work them in that order.

Symptom presentation

On a valid signal the strike energizes audibly (an AC strike buzzes, a DC strike clicks or hums quietly) but the keeper does not pivot freely, so pulling or pushing the door does not open it. Sometimes it releases if someone leans off the door first; sometimes it never releases. The buzz may sound strained or weak. A strike that is dead silent on signal is a different problem (no power or no signal), and a strike that releases but does not relock is a fail-mode or keeper-return fault, not this tree.

Quick checks

• Measure DC or AC voltage at the strike terminals, with the strike energized, under load. Do not measure at the power supply output, where it will read fine while the strike starves. Voltage at the strike below the part's rated minimum is the single most common cause of a buzz-but-no-release.
• Pull the door fully closed and relieve any pressure on it (push it open slightly toward the hinge side or lift weatherstrip load) while signaling release. If it releases the moment you take side-load off the latch, the keeper is preloaded and binding.
• Confirm the strike's voltage and AC/DC rating against the supply by part number. An AC strike on DC will not buzz correctly and may sit silent or hum; a DC strike fed AC may chatter and never fully pull the keeper free.
• Verify the fail mode matches the opening. A fail-secure strike releases only when energized; a fail-safe strike releases when de-energized. Confirm both that you ordered the correct mode and that it is wired to match the access-control and life-safety intent.
• Inspect the keeper travel by hand with the door open and the strike energized. The keeper should swing free through its full arc; if it catches or returns sluggishly with power applied, the fault is mechanical, not electrical.

Isolation tree

Branch 1: Voltage at the strike is below rated minimum under load. The buzz is the solenoid trying to pull in on insufficient current. Causes: undersized wire over a long run, a power supply sagging under load, or a shared circuit. Calculate voltage drop for the run; upsize the conductors or relocate the supply closer; confirm the supply's continuous current rating exceeds the strike's inrush and hold draw. Re-measure at the strike until it reads in spec, then re-test release.

Branch 2: Voltage is in spec but the door must be relieved of pressure to release. Latch preload. The door is sprung against the stop (over-tight weatherstrip, a closer holding it hard, or a warped door) and the keeper cannot pivot against the latch side-load. Verify the strike is rated for the preload present, reduce the door's closing force or weatherstrip pressure, and confirm a preload-rated strike if the condition cannot be eliminated. Many egress doors need a strike specified for the preload they routinely see.

Branch 3: Strike rating does not match the supply (AC vs DC). An AC strike buzzes by design and needs AC to release cleanly; a DC strike on the wrong supply chatters. Confirm the part number's input, match the supply, and re-test. Continuous-duty applications often require a DC strike; intermittent door-release buzz applications use AC.

Branch 4: Voltage in spec, no preload, correct AC/DC, still no release. Inspect the keeper for a mechanical jam, a binding return spring, or a horizontal/vertical misalignment between the latch and the keeper pocket. Adjust the strike position so the latch seats centered in the keeper and the keeper swings free when energized.

Confirming diagnosis

The fix is proven when the strike releases on the first valid signal, every time, with the door closed under its normal operating pressure, measured voltage at the strike inside the rated band under load. Cycle the release 20 times with the door fully shut. For a preload case, re-test after the closer and weatherstrip have settled to their working state. For a fire or egress opening, confirm the door still latches and self-closes correctly and that the fail mode matches the life-safety requirement before you sign off.

Remediation

• Voltage drop (Branch 1): upsize conductors, relocate or upsize the supply, verify in-spec voltage under load.
• Preload (Branch 2): reduce door pressure or specify a preload-rated strike; re-test under normal pressure.
• AC/DC mismatch (Branch 3): match strike input to supply per the part number; replace if mis-specified.
• Mechanical jam (Branch 4): realign the strike, free the keeper return, confirm a clean pivot energized.
• Document the fail mode and confirm code compliance on egress and fire openings.

References

• UL 1034, Burglary-Resistant Electric Locking Mechanisms (electric strike construction and performance).
• UL 10C, Positive Pressure Fire Tests of Door Assemblies (fire-door hardware and self-latching requirements).
• NFPA 101, Life Safety Code (means of egress, electrically controlled egress door requirements).
• BHMA/ANSI A156.31, Electric Strikes and Frame-Mounted Actuators (preload ratings, voltage, and fail modes).