In the last month, I noticed that the heating is not working properly, or it keeps blowing cold or hot, I removed the motor for moving the damper, took it apart, put it back and looked at everything correctly, not a single gear was broken, the damper arm moves slowly, after dismantling the motor everything works fine for a day or two and freezes again and nothing works. The motor, the potentiometer, the board was not damaged anywhere, I thought that the control panel for the air conditioning had failed, I planned to change it.
After looking for the possible cause of the failure of the heating on a website, I came across the same problem as mine, the problem was in the brushes on the motor, and I opened it to check the brushes, they look great, they are not worn.
The problem is that the brushes have become rounded and are not flat, but their contact surface on the rotor has increased and sometimes they catch two collectors and there is a short circuit, which is why the command to cool or heat is canceled, it does not respond to any command. The problem was solved in 5 minutes, I sanded the brushes with tweezers and sandpaper and gave them a bit of a conical fit on the rotor, it's been working as it should for a week now, I test it every day, hot, cold and some temperature in between, so far everything works great
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..on the brown and black wire there is current for hot-cold in which direction the engine should turn the valve, this was tested on the connector from the engine, it happens that there is current on both wires, it should not be like that, but it depends on only one of them which command is given, when it happens that there is current on both wires, it means that the brush has connected two collectors and the engine remains stuck, that is the reason for the cancellation
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.this is the incoming connector from the heating control, and there is always current on the wire to which the command is assigned, when it is inserted into the connector on the motor, current appears in two places, which means that the motor, the brushes are then connected
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