locked Re: tb/AMEL 54 outhaul protector burn out Mid Atlantic/AYOG + COVID

Bill Kinney


Darn it... I was so sure I had a good answer...

Let's see if I have a summary right... You have switched motors and both turn fine under zero load, but a bit of load and they bog down a lot, to the point of stopping. Weird... since the furling motor really doesn't work very hard under most conditions.  But... in kind of a stream of consciousness, here is my thinking...

I struggle to imagine how a straight piece of cable could have such a high resistance that the motor wouldn't run.  A connector at one end or the other, maybe...  If you were pulling 100 Amps through a high resistance connection it would be easy to find, it would be glowing red hot.  Literally.  That's 2500 watts of power, a lot more than a kitchen toaster uses.  Of course my failure in imagining, doesn't prove anything...

If you had not swapped motors and had the same problem, I'd look for a stuck brush...

I keep coming back to the mechanics on this one.  Is it possible that the gearbox is out of whack?

But then you said that the motor and gearbox run fine when not connected to the foil...  

With the sharp points on a multimeter's probes you should be able to go through the insulation right at the motor housing and get a voltage reading when running--or trying to!

If we assume the motor in not part of the problem, and also the manual furler and foil have been proven good, the only things left are the gearbox and the power supply.

Things I would try:  
  • Confirm that the current draw for the motor when stalled is 100A.
  • With motor and gearbox disconnected from the foil, measure the current when running. This should be low, maybe less than ten.
  • With the motor trying to run, measure the voltage drop in the positive wire from the battery to the relay.  It should be low, less than 1.5 volt.
  • Do the same from battery negative to the negative terminal the motor cable connects to.  Should have the same result.
  • Find a way to measure the voltage drop as close to the motor as possible when it is trying to run. This should be close to 24 volts.  if the voltage drop across the motor is much lower, there is a problem with the power delivery--somewhere. If the voltage drop across the motor is `24 volts, then the motor is getting power as it should.

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