Tower electric fan starts and stops continuously

[Afzal]

I have a tower electric fan which starts and stops continuously. I am very familiar with electricity but not so much with electronics. I have replaced a 1.5 microfarad capacitor which is connected to the motor to no effect. I have investigated further and found two electronic cards - one for the control switch buttons and one which is connected to the motor. The card contains 3 capacitors and one of these ( 0.1 microfarad) is connected across 2 wires which come from the motor windings. I have replaced it to no avail.
The motor still starts & stops continuously at the 3 speeds setting.
Would be grateful for some help.

 

[kellys_eye]

The motor may have an internal thermal trip - can you post pictures of the item?

 

[Afzal]

Thx for your response. Could you please tell me which pictures you are looking for exactly ?

 

[Afzal]

Thanks for your response. Could you please tell me which pictures you are looking for exactly.

 

[Afzal]

Thanks for your response. Could you please tell me which pictures you are looking for exactly?

 

[Afzal]

The motor may have an internal thermal trip - can you post pictures of the item?

The for your response. Could you please tell me which pictures you are looking for exactly?

 

[shrtrnd]

No one monitors these questions on a continuous basis. We check them intermittently.
kellys_eye will probably respond to your questions the next time he's visiting this website.
I believe he was asking for pictures of the motor to try to determine if the motor has an internal thermal interrupt device.
It would help us to help you, if you can tell us the manufacturer and model number of the motor, and any
motor control information (make & model number) if you know what they are (the 2 control boards you talked about).
Also, did you notice any burn or excessive heat damage to the boards, the components on them, or any circuit path traces on the boards or the wires connecting them.
kellys-eye suspects a thermal interrupt inside the motor itself, but if you can post pictures of the control boards, we
will have more information to help you solve this problem.

 

[Afzal]

Hi
Thanks for your info. Further to your suggestions I have opened the fan for further investigations.
1. From what I can see there is one electronic board for the various controls, namely, on/off, timer, swing, motor speed etc..
2. I have closely examined both sides of the board and there are no signs of overheating or sparking.
3. The second board is connected to the incoming power supply, to the swing motor and the fan motor.
4. This board as well has no signs of overheating or sparking.
5. I mentioned in my first post having replaced a 0.1microfarad connected across two wires coming from the main motor. That's not true. In these 2 wires are the incoming power supply and are also connected to an item that I cannot identify and a transformer.
6. I have taken some pictures of the electronic boards and the electric motor with a small wiring diagram of the windings. I hope to be able to upload them.

 

[Afzal]

Apologies. I haven't been able to forward the pictures as each time the uploading has failed

 

[kellys_eye]

Use an image editing program and change the size of them to something like 800x600 pixels (1024x768 will also work).

Sounds like your pictures exceed the forum size limit.

If the circuit boards incorporate solid-state thermal detection/cut-out devices then you won't 'see' anything untoward. But until WE see the board(s) we can't tell what you have.....

 

[Afzal]

Hi
Thx for reverting and advice about editing the photos. I will try and revert.
Just one comment though. The start/stop occurs as soon as the fan is switched on and the start/stop cycle is very short indeed - 1 to 2 seconds max. So personally I wouldn't say It's a thermal problem but then I am not the expert and would therefore look forward to your expert advice.

 

[Afzal]

 

[kellys_eye]

Ok, the big issue (for me) is that the power for the electronics on that control board is derived from a capacitive dropper circuit which means the board is 'live' at all times.

Motor speed looks to be selected by switching triacs in/out of circuit under control of the microcontroller that itself is powered from said capacitive dropper...... unless you have the correct test equipment and approach this very carefully you could be looking at dangerous electric shocks.

Try to establish the DC voltage at the microcontroller first (probably 5V) - you will need to find out the IC type number (printed on top of it) and check the datasheet to see which are the power pins but you could also check for it across the smoothing capacitor. We'd need a clearer picture of the board (picture 2) to establish which one that is - a picture with the wires out of the way......

 

[Afzal]

 

[Afzal]

Hi
Apologies for not reverting earlier as my internet service was down. If you need further info or any test you would like me to do in order to find the fault please let me know and I'll do my best.
Take care

 

[kellys_eye]

Could be me bit TR1 and (possibly) TR4 look to be physically damaged - can't really tell from the pictures. Maybe you can determine this yourself?

 

[Afzal]

Hi
Thanks again for your response. Looking again at the picture TR1 & TR4 do look a bit in bad shape but in reality they looked OK. Anyway I will replace them and see. Could you please tell me what they are and if possible their functions in that circuit ?
Thanks again for your patience and advice.

 

[kellys_eye]

All those devices are probably small triacs or thyristors - try to get the part number from the side of them and Google it.

The area in the picture below is the capacitor dropper circuit where the DC output is across ZD1 - this can be measured using your test meter. Take care as there is live mains voltages on the board.

 

[Afzal]

Hi
I have decided to replace the transistors(?) TR1 &TR4 and see if the problem is sorted out but now I am at a dead end ! They are both of reference C 2614 1A60 but they are not available locally. I have a contact in Paris and it is not available there either ( Not listed ). I have googled it but no response again !
Could you please do a small search and revert ?
Thanks a lot in advance. Take care.

 

[Afzal]

Hi
It's quite a while since my last post and I could not get replacement parts for the transistors/thyristors. In a last ditch attempt I have replaced TR1 by TR5 which is on the swing motor circuit just to see if there is any change. I am pleased to inform you that the fan now works on speed 2 & 3. It doesn't work on speed 1 and obviously it doesn't swing either.
I will now use it as is until I get replacement for the other transistors/thyristors or I buy a new one.
Thanks very much for your valued help & advice. Greatly appreciated.