Garage Doors – Repair Guide

Although products made by this brand are generally reliable, more or less serious issues may occur every now and then. Below you will find the Mighty Mule gate opener troubleshooting tips for the models that belong to the 50, 500, UL325, and FM402 series.

Mighty Mule 350 gate opener troubleshooting

Problems	Cause	Solutions
Audible/buzzer/alarm feedback:	1. 1 beep with 2 seconds off:	Limit switch error: Limit switch's normally open and normally closed inputs both open or both shorted. The alarm will automatically shut off in 4 seconds after the problem is corrected.
	2. 5 beeps with 2 seconds off:	Low battery condition detected: Low battery can occur if the following condition is detected: While in idle state and the battery voltage is below -11.5 Volts. While running and the battery voltage is below -10.0 Volts. The alarm will automatically shut off when the idle voltage is more than 12 Volt. The unit may continue to operate even when low battery is detected. The STATUS LED will also blink when the buzzer is beeping.
	3. 1 beep when attempting to run the unit:	No battery is connected. Blown fuse. Dead cell or extremely low battery condition.
	4. Alarm continuously beeps (Transmitter does not operate unit AND not at either limit):	Two consecutive obstructions have been detected without reaching the limit. Alarm will automatically shut off after 5 minutes. ‘Power-cycle’ the unit will also shut off the alarm.
	5. Learn Transmitter:	When a new code is learned from the transmitter the alarm will sound. Release the ‘LEARN Transmitter’ button will turn the alarm off.
	6. Power-Cycle:	The alarm will beep for 1 second upon power up.
Visual/leds feedback:	1. RF LED (LED2):	Blinking when there is 318 MHz signal is received. This LED is typically off when the receiver is connected and no 318 MHz signal is presented.
	2. STATUS LED (LED1):	While the unit is IDLE: 1 blink with 2 seconds off: Free Exit terminal is shorted to common. 2 blinks with 2 seconds off: Safety terminal is shorted to common. 3 blinks with 2 seconds off: Edge terminal is shorted to common. 4 blinks with 2 seconds off: Cycle terminal is shorted to common. LEARN LIMIT Mode: This LED will turn on when the ‘LEARN-LIMIT’ button is pressed. It will turn off after 3 seconds indicating that it has entered the learn limit mode (if not at the retracted limit) or cleared the previous learned limit (if at retracted limit). Whenever there is a change in state at any of the inputs this LED will blink once.
	3. POWER LED (Green):	ON: AC power or solar power is presented. OFF: NO AC power or solar power is presented.
	4. CHARGING LED (Red):	Red light on or flashing - the unit is charging Red light off - the unit is not charging. Check transformer or solar panel.
The gate closes then opens partially:	1. Check the position of the mounting brackets and readjust if necessary. 2. Check the gate for binding or hinge damage. 3. Increase Stall Force setting.
The gate opens then closes partially:	1. Check the position of the mounting brackets and readjust if necessary. 2. Check the gate for binding or hinge damage. 3. Increase Stall Force setting.

Mighty Mule 500 UL325 series gate opener troubleshooting

Symptom	Diagnosis	Check:
1 short beep upon activation	Blown Fuse Low or Bad Battery Loose Battery Connection	• Fuse • Battery Under Load • Battery Harness Connections
1 short beep upon power up	Circuit Board Powered Up & Ready	• Normal Operation
Continuous Uninterrupted Alarm	Circuit Board Senses an Obstruction	• Path of Gate • Gate for Level and Plumb • Stall Force Adjustment • Disconnect Safety Devices • Rev Counter
1 beep with 10 seconds off	Low Batter)' Condition	• Fuses • Battery Harness Connections • Battery Under Load
1 beep then 2 beeps	Master Motor Terminals Shorted	• Connections to Master Inputs • Master Arm Power Cable • Motor • Circuit Board
1 beep then 3 beeps	Slave Motor Terminals Shorted
1 beep with 2 seconds off	Master Arm Limit Switch Error	• Connections to Master Inputs • Master Arm Power Cable • Master Input ORG & GRN. BRN & GRN voltage with wires disconnected. 11VDC across each terminal.
2 beeps with 2 seconds off	Slave Arm Limit Switch Error
3 beeps with 2 seconds off	Master Arm Rev Counter Error	• Connections to Master Inputs • Master Arm Power Cable • Rev Counter
4 beeps with 2 seconds off	Slave Arm Rev Counter Error
Status (clear) 1 blink	Cycle Terminal Shorted	Disconnect the push button, keypad, intercom keypad, or any other accessory wired to this terminal. Try the remote. If the remote works, then the problem is the accessory.
Status (clear) 2 blinks	Safety Terminal Shorted	Disconnect the loop detector, photo beam, or any other accessory wired to this terminal. Try the remote. If the remote works, the problem is the accessory.
Status (clear) 3 blinks	Exit Terminal Shorted
Status (clear) 4 blinks	Shadow Terminal Shorted
Status (clear) 5 blinks	Close Edge Terminal Shorted	Disconnect the edge sensor, photo beam, or any other accessory wired to this terminal. Try the remote. If the remote works, the problem is the accessory.
Status (clear) 6 blink	Open Edge Terminal Shorted
RF (yellow) Flickers	Receiving 318 MHz RF	Normal operation when remote or wireless keypad is used.
RF (yellow) OFF	No 318 MHz RF Received	• Battery in Remote • Program Remote • Antenna Receiver Connections • Antenna Receiver
Power (green) ON	AC or Solar Power Present	Normal Operation
Power (green) OFF	No AC or Solar Power	Transformer: • Breaker or GFI • Power at AC outlet. • Output of Transformer. • Voltage on wire at 18 VAC Input Solar: • Solar Panel Wires Reversed • Weather • Solar Panel Placement • Output of Solar Panel • Voltage on wire at Solar Input
Charge (red) ON	Fast Charging Mode	Battery Voltage should be -14.8 VDC when connected to the circuit board
Charge (red) Fast Blinking	Soak Charging Mode	Battery Voltage should be -14.1 VDC when connected to the circuit board
Charge (red) Slow Blinking	Float Charge	Battery Voltage should be -13.8 VDC when connected to the circuit board
Charge (red) OFF	Battery Not Being Charged	• AC power • Transformer • Solar Panel • Charging Circuit

Mighty Mule FM402 gate opener troubleshooting

Symptom	Diagnosis	Solutions
Visual indicators	Power LED (Green)	• ON: AC power or Solar power is present. • OFF: There is no input power.
	Status LED (Yellow): (while unit is running this LED will be OFF)	• Rapid blinking in random pattern: GTO’s transmitter 318 MHz signal is detected. • Continuously ON: Battery is in fast charge mode. • 1 Blink every 2 seconds: Battery is in float charge mode (battery is fully charged) • OFF: Switch is in the OFF position or there is no input power for at least 60 seconds.
Audible indicators (alarm/buzzer)	Beeps upon power up	• This is normal self test when the unit is turned on.
	Continuous beep after power up	• Unit has learned new transmitter code, releasing the transmitter button will shut off the alarm.
	Rapid beeping	• Unit has encountered two (2) obstructions without reaching either limit. (Power cycle to reset the alarm) • Transmitter will not operate the gate. • Alarm will automatically shut off after 5 minutes; gate will remain disabled until control box is restarted.
	1 beep every 20 seconds	• Low battery is detected.
	1 beep every 2 second	• Position sensor is open circuit. Call GTO Service department.
	2 beeps every 2 second	• Position sensor is short circuit. Call GTO Service department.
	1 beep when attempting to activate the opener:	• Blown fuse. • Battery is extremely low or damaged. • Loose connection from battery to circuit board.
If the gate stops and reverses direction	1. Check the gate for binding or hinge damage. 2. Adjust stall force if necessary. 3. Reprogram closed position limits. 4. Check the position of the mounting brackets and readjust if necessary.

Mighty Mule Automatic Gate Opener SystemFOR DUAL SWING GATES gate opener troubleshooting

Problem	Cause	Solution
Check the Green LED on the Control Board:	IF THE LED IS OFF: This condition indicates a transformer power failure.	1. Test the transformer for voltage with a voltmeter. The acceptable range can be found in the VOLTAGE LIMITS chart. If the transformer test shows no voltage, then test the electrical outlet for voltage. If the outlet test shows voltage, then the transformer is dead and must be replaced. Allow the new transformer 12 hours to charge the battery before using the gate openers. 2. If the transformer test shows voltage, check the POWER IN terminal block on the control board for voltage. If the terminal block shows no voltage, look for broken or spliced wires.
Check the Red STATUS LED on the Control Board:	IF THE LED IS ON: This condition indicates the control board is powered up.	1. Replace the transmitter battery with a fresh one. 2. Verify that the power cables are securely connected. 3. Replace the control board fuses if they arc blown (15 ampere fuses only - DO NOT USE HIGHER RATED FUSES!).
	IF THE LED IS OFF:	1. Make sure the ON / OFF switch at the bottom of the control box is set to ON. 2. Check all connections for looseness and corrosion. 3. Make sure the batter)' cables arc connected.
	IF THE LED IS FLASHING:	The system may be in a condition known as ’low voltage lockout" (i.e., inadequate voltage supplied for the gate opener to function). 1. Test (using a voltmeter) the voltage output of the transformer (18.0 to 22.0 VAC) or solar panel (18.0 to 22.0 VDC) at the control board power terminal block. A. If the voltage is low or not reading, load test the batter)' at a electronics store and call your dealer for a replacement batter)' if necessary. B. If the voltage is low or not reading, test the transformer and electrical outlet. Replace the transformer if necessary and let the batter)- recharge for 12 hours before using the gate opener. C. Check the control board for damage or corroded connections. D. Make sure that telephone or solid core wire is not being used to connect the transformer to the control board.
The Gate CLOSES Then Opens Again on its Own:		1. Check the position of the mounting brackets and readjust if necessary. 2. Check the gate for binding or hinge damage. 3. Check the position of the stroke adjustment knob.
The Gate OPENS Then Closes Again on its Own:		1. Check the position of the mounting brackets and readjust if necessary. 2. Check the gate for binding or hinge damage. 3. Check the position of the stroke adjustment knob.
One Gate OPENS and the Second Gate Doesn't in a DUAL Gate Application:		1. Check the DIP switches on the control board and be sure the SNGL/DUAL is set to DUAL. 2. Check the Opener Power Cable for proper connection. 3. Check the fuse.

The Mighty Mule brand belongs to GTO Access Systems. Unlike the Linear Pro Access brand, that is also the property of this company, Mighty Mule openers are designed for Do-It-Yourself customer. The company’s history started in the 1980’s in Florida.