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Motor current warning; one motor hot after landing

RaidPW

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#1
I apologise for posting another thread on what seems to be a common problem, but I do have a specific question about it.

I took my refurb Mavic Air out for its first flight today, in 23c weather with no wind, and thirty seconds after takeoff, while flying slowly forwards and upwards, I notice the "Motor current error. Check your propellers and fly with caution" message in the app. I keep my eye on the aircraft and it appears to be flying perfectly normally, not making any unusual sounds or moving erratically. I do a slow, clockwise circling descent and land. I check the propellers as instructed, but notice the rear-right motor is significantly hotter than the others, but all propellers appeared to be seated properly and undamaged.

I try a second flight and the same situation occurs, so again land carefully. The same motor is still hot to the touch, not painfully so but I wouldn't want to hold my finger on it for very long. The aircraft was flying for no more than 6 minutes between the two flights and only performing very gentle maneuvers. I've since searched the DJI forums and have seen plenty of other people reporting the error message (since the .400 firmware update, which came pre-installed on mine), but nobody has mentioned the hot motor. DJI reps have claimed that it's just an error with the app and that it's safe to ignore, but at least in my case the hardware seems to be affected.

Has anyone else with the same error message noticed any of the motors being hotter to the touch than the others? It does suggest that this motor is working harder than it should be, though I can't see any obvious physical reason for it - it rotates just as easily by hand as the others do. I suspect I'll need to RMA the aircraft anyway (I'm not confident flying an aircraft when there's likely a problem with one of the things keeping it in the air), but I'd be interested to see whether this is a symptom of the firmware issue or whether my case is unique. I'm going to perform just a basic hover test tomorrow to see if it happens when the aircraft isn't moving, using one of the spare propellers.
 

mad monkey

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#2
Does this error have an audible message/noise too?

I'm not always watching the screen of course and don't want to miss it if it happens to me
 

RaidPW

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#3
Not that I noticed, but this was my first flight of a DJI drone in over a year, and there are so many alert noises in the app that it's possible I mistook it for something else.

If you upload your flights to a service like Airdata, it does list instances of the warning as tips.
 

RayOZ

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#4
Is the refurb from DJI? Use your fingers to manually spin the motor and feel for any resistance. Maybe it's rubbing against something (dirt?) when spinning, which would explain temperature increase.
 

Simmo

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#5
I wouldn't even contemplate flying it again?!
If you can notice a differance in motor temp, there is definately a problem.
Take it back, get another one.
 

RaidPW

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#6
Is the refurb from DJI? Use your fingers to manually spin the motor and feel for any resistance. Maybe it's rubbing against something (dirt?) when spinning, which would explain temperature increase.
I did say in the original post that it rotates no differently than the others. It wasn't bought from DJI themselves, but it is apparently refurbed by them. I don't think DJI sell refurbs directly in the UK, it was bought from Scan.co.uk.

If you can notice a differance in motor temp, there is definately a problem.
Clearly it's a problem, and don't worry, I wouldn't risk flying the thing properly. I'm just curious as to whether this problem is caused by a simple mechanical fault with the motor or whether the firmware problem is causing an incorrect amount of power to be sent to one motor.
 
Likes: GlenS

RaidPW

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#7
I've arranged a replacement from the retailer. I tried the hover test just in my garden with one of the spare props (no more than a meter off the ground, it presumably would have survived a fall from that height had the motor actually failed), and even then it was happening. After only a few minutes in the air the same motor was scalding hot. Clearly it's unsafe (that much was obvious after the first flight), but I'm still curious as to whether this is the same problem that many others have been reporting or something entirely different that just happens to present the same error message.

If it's the former, then I would consider any aircraft with the most up to date firmware to be unsafe, and the advice from DJI reps that it's safe to ignore to be irresponsible.
 
Last edited:

Congoblue

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#8
I don't see how it could be a firmware problem - the firmware controls the motor power to keep the aircraft stable. Therefore it must be struggling to get the required lift on that motor and feeding extra power to keep the position. If "too much power" was sent to a normal motor it would make the motor spin faster and make the aircraft flip over. Gotta be a mechanical problem with the motor.
 

RaidPW

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#9
I imagine you're right, but these things are more complicated than the average layman like myself sometimes gives them credit for so I don't like to assume it's a simple fault.
 

RayOZ

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#10
For a temp problem, it’s more likely mechanical. Either it’s rubbing against something inside, or the wiring is exposed and minor short between the windings.
At least you can get a replacement. Best solution.
 

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