As the title says. How the heck can a blend motor short to positive when it is mounted onto a pcb
which is encased in plastic, then screwed to a plastic box?
I have had an entertaining day chasing my Right hand blend motor shorted to ground issue.....
Removed, tested, cleaned, replaced. Same error.
Tried 3 different, known good HVAC heads. Same problem.
Swapped in a used replacement. Problem went away! Only to reappear as "Potentiometer feedback circuit failed" (or something like that)
Put in a 3rd B/M after testing, cleaning, and re testing. This one faulted with Motor shorted to positive.
Took the motor out of the one with Pot failed error, and put it in the one with Motor shorted issue.
Got motor shorted error on this one.
I am thinking now that the caps on the B/M PCB are the issue as they will die with age.
How else could stray current trigger a fault?
Tomorrows job will be to remove these caps and see what is happening.
I am sure they are there to filter the noise from the brushed motor, Worth a try...
I will source replacements and try that if no joy.
If Marty was around, I am sure he would have a better plan.
I am open to suggestions.
I will report back tomorrow......

Another of the many odd error messages that the Nanocom gives. While it may, usually, correctly identify which component is at fault, the fault description doesn't always correspond with what the actual fault is.

The faults with blend motors are either a failed, or intermittent, motor or glitches in the feedback pot so it doesn't give a steadily changing output.

Well, Yes.......That would be nice if it did not make stuff up or mis report.
I have a good smooth motor, and a clean Pot as tested on an analog meter. Smooth sweeps.
Clipping the cap out did get rid of the motor shorted error, but I got the persistent pot failed error.
As the plug for the blend motors was cracked, I soldered in a replacement from the spares cabinet.
This has cleared up the issues with the RH blend motor.
NOW I am getting feedback failure error from the LEFT blend motor!
I am a decent solderer so I doubt I screwed up a join.
In addition, I noted that when testing the pushbuttons on several HVAC controllers, The Nano reports,all
of the LH buttons to be on the RH side and vice verse.
I have found other things that the Nano is dyslexic about so I am now left wondering if it is cross reporting issues?

Back at it!

If you go to the Nano Inputs - Values page, and then adjust the temperature settings on each side while watching the feedback value, that will confirm, or otherwise, that you are looking at the correct one.

Great tip!
I will report the results.
In the meantime, it appears that aging filter caps in the blend motors may just be behind the "Shorted to positive"
syndrome. I clipped out the offending part on the board, and the problems all went away!
The LH Pot issue as well as the right as suspected, stemmed from a cracked blend motor plug keeping the contacts for
the 2 white wires (Potentiometer LH and RH) from making consistent contact.
So, all good for now. I will be curious if anyone who has the shorted to Pos issue is able to duplicate my results?
I know there are a couple of blokes out there with HVAC test bed setups. Possibly try it out?
It would be nice to not have to purchase new BMs if it's only a failed cap.
There are no adverse effects that I can see from not having it there, but I suppose it could be replaced if needed. Very small value ceramic cap.

I have noticed the same left-right wierdness with Nanocom. Sent them a message on the Nano forums about it, but never got any reply.

I too have odd behaviour in one P38 with left blend. The motor & pot definitely work fine when powering from a 9V battery, but calibration & the manual check in the Nano utility always fails. The 16-pin connector has been replaced with new, because the contacts definitely become intermittent with age.

Had to replace the driver chip in a couple of HEVAC's but now I have a bench test setup including a spare heater box & good working set of motors.
HEVAC Bench Test

I thought you were one of the guys with a test bed.
Have you got any blend motors that come up with a motor shorted to positive error?
If so, I would be curious to see if removing the small capacitor gets rid of the error.
Several days and drive cycles later, the errors have not returned and the lack of the Cap
hasn't caused any other issues........