air conditioner high-low voltage error

[DPG]

Marconi, if you've managed to pinpoint this fault down to component level just by forum messages then I'm very impressed.

Obviously if this isn't the fault then I'm not impressed.

Full marks to the OP for providing good information as well.

 

[dodo41]

I could only rotate it 1 time. And the plastic on the potentiometer broke because I forced it. Maximum 0,37v. I could read. However, the air conditioner did not work again.

 

[DPG]

I could only rotate it 1 time. And the plastic on the potentiometer broke because I forced it. Maximum 0,37v. I could read. However, the air conditioner did not work again.

Are you competent to replace the pot?

 

[marconi]

It only operates - as a clock - over say 1 o'clock to 11 o'clock.

Do you have a small soldering iron?

Send me a Private Message(PM) with your address and I will post you a replacement potentiometer - it needs replacing anyway so do not be upset.

Meanwhile, turn your meter to dc amps 200mA at 7 o'clock on your meter.

Connect red lead to voltage position V1 and black lead to voltage position V3. This will apply 12 V directly to the microcontroller.

 

[dodo41]

red tip J28
black tip J25

Should I connect this way?

 

[marconi]

yes that is what I mean.

 

[dodo41]

I tried but it didn't work

 

[marconi]

That is disappointing.

I have not given up. I will contact you again tomorrow.

Marconi

 

[dodo41]

I'm waiting for you. Thank you

 

[marconi]

Right - we need to replace the blue potentiometer which is now broken. First I need to know the colours of the stripes on resistor R40.

Do you have a small soldering iron and solder? I would use one like this:

Antex S27J470 C15 15W Soldering Iron 230V Silicone Cable British Plug - https://www.rapidonline.com/Antex-S27J470-C15-15W-Soldering-Iron-230V-Silicone-Cable-British-Plug-85-5546?IncVat=1&pdg=aud-810679295195la-301834893510:kwd-301834893510:cmp-757438067:adg-44804851896:crv-207912323492id-85-5546:dev-c&gclid=CjwKCAjw7LX0BRBiEiwA__gNw3TLgyd3U4o4jVs-RCPANzj7yb5eCw8r9XPpqrirbpSxevBvdgNfhBoCWLMQAvD_BwE

What the last test did indicate - I cannot be absolutely sure - is that the mains voltage voltage sensing by the microcontroller detects 'too high' as well as 'too low'.

 

[dodo41]

Brown-Brown-Black-Black-Orange

What happens if I don't change the potentiometer?
I don't want to go out

Would it be a problem if we change the potentiometer another time?

 

[marconi]

I have contacted Rapid Electronics UK a supplier of electronic components which I use regularly. You can buy a replacement potentiometer from them. You need to buy some of these:

Suntan TSR-065-102-R 1K 30% LIN 0.1W Trimmer - https://www.rapidonline.com/Catalogue/Product?Id=68-1574

They are only 14 pence each so buy a few - just in case.

Be careful to order the item 68-1574 which has a resistance of 1kOhms.
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Could you measure the resistance of R40 for me please - it should be about 3000 Ohms.

If you send me you address in the PM(Private Message) area of the EF I will buy and send them to you - the cost is negligible so don't worry about paying me back.

Yes we do need to replace the potentiometer. Do you have a soldering iron and some solder?

 

[dodo41]

Yes, I have a soldering iron and some solder.

It values between 2.9 and 3 kOhm.
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However, it may take some time before I change the potentiometer due to Covid-19.
I may have problems in procurement.
I will try to act as fast as possible.

 

[marconi]

Procurement - what about using rapid electronics UK - I sent you a link in my earlier message?

 

[dodo41]

Okay. I will order.
Do you think the problem will be improved when you change the potentiometer?

 

[marconi]

Ref; Message #37.

Yes I do - but I cannot be certain - we have definitely found one thing that is wrong. There should have been a voltage between 9 and 12Volt sent from the potentiometer to the microcontroller - this was voltage V3. You measured V3 to be 0V.

Additionally, there should have been a voltage of 9V across R40 - this was voltage V2 - and you measured 0V. This indicated that the potentiometer was faulty - open circuit somewhere along its resistive track - so no current was flowing through the potential divider formed by the pot' and R40 across the 12V supply. The little power supply to this circuit was fine - it has an output of 12V dc - this was voltage V1.

The typical voltage range for an air con like yours is 198 - 242V. The voltage V3 is proportional to the input voltage and monitored by the microcontroller to detect whether the mains voltage is 'too high.

If it was my air con I would be changing the pot.

 

[dodo41]

First I will change the potentiometer.
Thank you.

 

[marconi]

The attachment might help you follow what we have been doing.

 

[dodo41]

I Replaced Trimpot. But I did not energize.
I'm waiting for you, Mr. Marconi.
Please review and tell me what to do.
I set Trimpot to Full center.

 

[Mike Johnson]

Impressive diagnostic's and information, hope it works after all this.