On command, Gate Motor runs briefly then stops. Should I replace the cap with a start/run cap?

Thread Starter

wildhobo

Joined Apr 9, 2017
5
On command, new single phase 125 VAC gate motor runs briefly, then stops. Motor supplier specifies a 25 µF cap. I have replaced the cap with similar results. Will a "run" cap of higher µF be sufficient to start and run? Or must I expressly order a "start/run" capacitor and if so, what values?
 

#12

Joined Nov 30, 2010
18,223
I have never seen messing with the run capacitor fix anything like this in 40 years of work. You already installed the capacitor that came with the motor. You already replaced the capacitor and it didn't fix anything. How many times will you replace the capacitor before you believe it won't fix anything?
 

drc_567

Joined Dec 29, 2008
1,156
What type of "gate" are you talking about?

Routine diagnostic procedures include:
1. Turn off power
2. Get a spray can of electronic contact cleaner
3. Disconnect the accessible wires, sensors, and other obvious problematic parts and spray with contact cleaner ... gets rid of grease, dirt, etc.
4. Look for irregularities, anomalies, and whatever parts would logically cause the difficulty.
 

MaxHeadRoom

Joined Jul 18, 2013
23,923
Try and run the motor off load, if possible.
It is not usually the capacitor if the motor actually starts, if it runs briefly and stops it could be loading, but check the voltage at the motor when the stop occurs.
Max.
 

Thread Starter

wildhobo

Joined Apr 9, 2017
5
What type of "gate" are you talking about?

Routine diagnostic procedures include:
1. Turn off power
2. Get a spray can of electronic contact cleaner
3. Disconnect the accessible wires, sensors, and other obvious problematic parts and spray with contact cleaner ... gets rid of grease, dirt, etc.
4. Look for irregularities, anomalies, and whatever parts would logically cause the difficulty.
 

Thread Starter

wildhobo

Joined Apr 9, 2017
5
Thanks for your suggestion. I think it's more than contact cleaner will fix but I shall double check. My driveway single leaf swing gate is remote controlled, via key pads or the landline phone. Two laser interruptors reverse on close to help avoid injuries or damage to card entering or leaving the property. I have replaced one that was obviously not working, with a brand new one.
The replaced capacitor bore markings showing it was a 60µF capacitor. I have not yet checked it. The gate computer's Manufacturer instructions manual specifies a 25 µF capacitor. I have replaced the capacitor with a new one of equal capacitance but the results were the same: the gate begins to close, then stops and won't react to new commands.
I have been relying on mostly forgotten electric knowledge acquired many decades ago in circuits classes. So, I apologize for displaying my current ignorance with the following couple-3 questions:

1. What short/long term risk is there when coupling a 60 µF capacitor to a motor rated for a 25µF capacitor?
2A. A start capacitor provides the motor's windings the necessary impulse to get the rotor turning, then stops providing the impulse. A run capacitor of reasonable size is normally too weak to do what a start capacitor is intended to do. Dual capacitors are intended to provide power to 2 separate motors.
Would a higher rated run capacitor, say 60 µF, do what a start capacitor would normally do, then support the windings to provide smooth power when the motor starts to run?
2B. "Start-run" capacitors are advertised on the web. How can a capacitor be both "start" and "run"?
2C. Should I enquire into more than just the capacitor's farad rating but also coulombs?
Thanks in advance.
Yvon.
 

Thread Starter

wildhobo

Joined Apr 9, 2017
5
Try and run the motor off load, if possible.
It is not usually the capacitor if the motor actually starts, if it runs briefly and stops it could be loading, but check the voltage at the motor when the stop occurs.
Max.

Thanks. The motor is inside a gate actuator assembly. Running the motor off load will be easy. The motor actuates a piston which pushes or pulls a gate shut or open. All I need to do is to disconnect the piston. Testing the voltage at the motor should be equally easy, except that testing should be done at the closest junction box which is located in an awkward position I prefer not to work in. So, I'll try the next best, testing power connections in an electrical box more easily accessible but more distant from the motor.

Meanwhile, I have a couple-3 questions:
My gate is remote controlled, via key pads or the landline phone. Two laser interruptors reverse on close to help avoid injuries or damage to card entering or leaving the property. I have replaced one that was obviously not working, with a brand new one.

The replaced capacitor bore markings showing it was a 60µF capacitor. I have not yet checked it. The gate computer's Manufacturer instructions manual specifies a 25 µF capacitor. I have replaced the capacitor with a new one of equal capacitance but the results were the same: the gate begins to close, then stops and won't react to new commands.
I have been relying on mostly forgotten electrical knowledge acquired many decades ago in circuits classes. So, I apologize for displaying my current ignorance with the following couple-3 questions:

1. What short/long term risk is there when coupling a 60 µF capacitor to a motor rated for a 25µF capacitor?
2A. A start capacitor provides the motor's windings the necessary impulse to get the rotor turning, then stops providing the impulse. A run capacitor of reasonable size is normally too weak to do what a start capacitor is intended to do. Dual capacitors are intended to provide power to 2 separate motors, not start for one and run for the other.
Would a higher rated run capacitor, say 60 µF, do what a start capacitor would normally do, then support the windings to provide smooth power when the motor starts to run?
2B. "Start-run" capacitors are advertised on the web. How can a capacitor be both "start" and "run"?
2C. Should I enquire into more than just the capacitor's farad rating but also coulombs?
Thanks.
Yvon
I have never seen messing with the run capacitor fix anything like this in 40 years of work. You already installed the capacitor that came with the motor. You already replaced the capacitor and it didn't fix anything. How many times will you replace the capacitor before you believe it won't fix anything?
No, no capacitor came with the motor. I replaced the old motor with a new one because the assembly leaked despite several attempts to stanch the leak. Then I tried to make the old capacitor rated 60 µF (which had worked with the original motor for some 20 years) to work with the new assembly and that didn't work. So I replaced the old capacitor with a new one as rated by the assembly manufacturer. That didn't work. So, where's the problem? A bad new motor? Possible and will bench test it. If that does not work, the problem may be in the computer, but that's a long shot.
Meanwhile, I do not want to risk a new motor rated for a 25µF capacitor energized with a new 60µF capacitor. If there is no risk, perhaps the 60µF run cap will act as a start capacitor. I'd just like to know if that theory holds. I would also like to know how can a capacitor be both start and run, as advertised on the web.
 

MaxHeadRoom

Joined Jul 18, 2013
23,923
You need to determine if the motor ceases getting power when it stops, rather than being stalled by some other means.
There are two types of cap start motors cap start/run with the cap in circuit the whole time or cap in until switched out by some means.
There are also motors that have both types of caps fitted.
The cap in each case are typically of different construction.
The size should be as close as possible to the Manuf original rating.
Max.
 

Tonyr1084

Joined Sep 24, 2015
6,459
I have a garage door opener. Same SORT of thing but obviously nothing like what you have. With my GDO, if there's something wrong with the beams or something is blocking it the motor will start to close then reverse to full open. However, there IS a way around that - HOLD the close button for the duration of the closing process. If the motor runs the full duration (or stops and reverses the moment you let go of the button then it's not the motor, but something else telling the gate to swing to the safe open position.

Another problem I've encountered was a failed "Motion Detector Circuit" (MDC) that sensed when the motor was moving. IF it didn't sense the movement it would immediately stop the power to the motor. So there's a second possibility for you to investigate. Failed or blocked beams; or a failed MDC. There COULD be other issues as well.
 

Thread Starter

wildhobo

Joined Apr 9, 2017
5
Thanks. The motor is inside a gate actuator assembly. Running the motor off load will be easy. The motor actuates a piston which pushes or pulls a gate shut or open. All I need to do is to disconnect the piston. Testing the voltage at the motor should be equally easy, except that testing should be done at the closest junction box which is located in an awkward position I prefer not to work in. So, I'll try the next best, testing power connections in an electrical box more easily accessible but more distant from the motor.

Meanwhile, I have a couple-3 questions:
My gate is remote controlled, via key pads or the landline phone. Two laser interruptors reverse on close to help avoid injuries or damage to card entering or leaving the property. I have replaced one that was obviously not working, with a brand new one.

The replaced capacitor bore markings showing it was a 60µF capacitor. I have not yet checked it. The gate computer's Manufacturer instructions manual specifies a 25 µF capacitor. I have replaced the capacitor with a new one of equal capacitance but the results were the same: the gate begins to close, then stops and won't react to new commands.
I have been relying on mostly forgotten electrical knowledge acquired many decades ago in circuits classes. So, I apologize for displaying my current ignorance with the following couple-3 questions:

1. What short/long term risk is there when coupling a 60 µF capacitor to a motor rated for a 25µF capacitor?
2A. A start capacitor provides the motor's windings the necessary impulse to get the rotor turning, then stops providing the impulse. A run capacitor of reasonable size is normally too weak to do what a start capacitor is intended to do. Dual capacitors are intended to provide power to 2 separate motors, not start for one and run for the other.
Would a higher rated run capacitor, say 60 µF, do what a start capacitor would normally do, then support the windings to provide smooth power when the motor starts to run?
2B. "Start-run" capacitors are advertised on the web. How can a capacitor be both "start" and "run"?
2C. Should I enquire into more than just the capacitor's farad rating but also coulombs?
Thanks.
Yvon


No, no capacitor came with the motor. I replaced the old motor with a new one because the assembly leaked despite several attempts to stanch the leak. Then I tried to make the old capacitor rated 60 µF (which had worked with the original motor for some 20 years) to work with the new assembly and that didn't work. So I replaced the old capacitor with a new one as rated by the assembly manufacturer. That didn't work. So, where's the problem? A bad new motor? Possible and will bench test it. If that does not work, the problem may be in the computer, but that's a long shot.
Meanwhile, I do not want to risk a new motor rated for a 25µF capacitor energized with a new 60µF capacitor. If there is no risk, perhaps the 60µF run cap will act as a start capacitor. I'd just like to know if that theory holds. I would also like to know how can a capacitor be both start and run, as advertised on the web.[
I have a garage door opener. Same SORT of thing but obviously nothing like what you have. With my GDO, if there's something wrong with the beams or something is blocking it the motor will start to close then reverse to full open. However, there IS a way around that - HOLD the close button for the duration of the closing process. If the motor runs the full duration (or stops and reverses the moment you let go of the button then it's not the motor, but something else telling the gate to swing to the safe open position.

Another problem I've encountered was a failed "Motion Detector Circuit" (MDC) that sensed when the motor was moving. IF it didn't sense the movement it would immediately stop the power to the motor. So there's a second possibility for you to investigate. Failed or blocked beams; or a failed MDC. There COULD be other issues as well.
You need to determine if the motor ceases getting power when it stops, rather than being stalled by some other means.
There are two types of cap start motors cap start/run with the cap in circuit the whole time or cap in until switched out by some means.
There are also motors that have both types of caps fitted.
The cap in each case are typically of different construction.
The size should be as close as possible to the Manuf original rating.
Max.
You need to determine if the motor ceases getting power when it stops, rather than being stalled by some other means.
There are two types of cap start motors cap start/run with the cap in circuit the whole time or cap in until switched out by some means.
There are also motors that have both types of caps fitted.
The cap in each case are typically of different construction.
The size should be as close as possible to the Manuf original rating.
Max.
Thank you very much. Yours is the best answer so far. This is getting now somewhere but it's pretty clear I'll want to have a talk with the supplier of my hydraulic arm, to make sure I don't burn the motor up or hurt myself in the process. Have anice day.
Yvon.
 
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