Liftmaster 29-40089, PIEZO ALARM
The LiftMaster 29-40089 piezo alarm is an audible service component used in the warning/alarm circuit on select commercial gate operators. In many gate systems, the alarm is not just a convenience buzzer; it alerts users and technicians to an operator condition that needs attention. Depending on the operator, an audible alarm can be tied to entrapment protection, obstruction events, alarm shutdown, or other monitored control behavior. A failed piezo alarm may be silent when a warning should sound, while a constantly sounding alarm can indicate a real system fault. This replacement should be matched by part number and wiring diagram. Do not bypass the alarm circuit or ignore the fault that caused it to activate.
Compatible With
- For use with various LiftMaster commercial gate operators when the parts diagram specifies 29-40089.
- Commonly associated with LiftMaster commercial slide gate operator alarm circuits.
- Shown in SL930-related parts references by some suppliers; verify by operator diagram.
- May be listed as a Sonalert piezo alarm in service parts catalogs.
- Not a universal alarm for all LiftMaster gate, garage, or access-control products.
Features & Specifications
| Manufacturer | LiftMaster / Chamberlain Group |
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| Product Type | Piezo alarm / audible alarm |
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| Part Number | 29-40089 |
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| Application | Commercial gate operator warning or alarm circuit |
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| Compatible Operator Type | Select commercial gate operators |
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| Common Reference | Sonalert piezo alarm |
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| Notes | Verify voltage, wiring, and operator alarm circuit before ordering |
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Also Known As / Related Part Numbers
- 29-40089
- LM-29-40089
- LiftMaster 29-40089
- 29-40089_A
- Sonalert piezo alarm
- Piezo alarm
- Commercial gate operator alarm
Technician Note
If the alarm is active, review the operator diagnostic condition before replacing parts. A stuck obstruction input, failed entrapment device, control-board issue, or reset procedure may be involved.
Before Ordering
- Match the old alarm to 29-40089.
- Check the operator manual for alarm-circuit wiring.
- Verify voltage and terminal/connector style.
- Inspect for water intrusion or wiring damage near the alarm.
- Diagnose the cause if the alarm is sounding continuously.
Important Ordering Warnings
- Do not bypass audible alarm or safety warning circuits.
- A silent alarm can create an unsafe service condition.
- A constantly sounding alarm may indicate a system fault, not a bad alarm.
- Use only where the parts diagram calls for this alarm.
Professional Advisory
Electrical components should be installed and tested by a qualified gate technician. Disconnect power before service and do not bypass safety devices, overload protection, alarms, or manufacturer-required entrapment protection devices.
Product Questions & Answers
What is the purpose of the 29-40089 piezo alarm?
It provides an audible warning or alarm signal in select LiftMaster commercial gate operator circuits.
Does a sounding alarm mean the alarm itself is bad?
Not usually. A sounding alarm often means the operator is reporting a fault, obstruction, entrapment, or control condition that must be diagnosed.
Can the alarm be disconnected if it is annoying?
No. Do not bypass or disconnect warning and alarm devices to keep the gate running. The cause of the alarm should be corrected.
Is this alarm used on SL930 operators?
Some supplier references associate 29-40089 with SL930 parts lists, but the installed model and wiring diagram should be verified.
What should be checked before replacing the alarm?
Confirm the part number, wiring style, operating voltage, and whether the operator is triggering the alarm because of another issue.
