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  1. #1
    Join Date
    Nov 2007
    Location
    central Nebraska
    Posts
    50

    Manitowac ice probe signal

    This is my first post in a long time; just an electrician trying to learn something as I am being trained to take over for the guy who will be retiring in the near future.

    I did not copy the Manitowac model number from today's service call, but the ice maker would not go into harvest. It was pretty obvious (even to a clueless wire-biter) that it was getting a constant signal from the ice probes.
    I cleaned the two probe tips with Scotch-brite, ran cleaner thru the water system and sanitized the ice bin. It ran thru 2 harvest cycles just fine.
    I do have a couple questions about these ice probes.
    1. Disconnecting the probe wires from the mother-board, should the resistance of the probes change from very high (not touching any ice) to zero (contacting the ice) or are they similar to a CAD cell where the board is looking for an intermediate value?
    2. What do you recommend to use for cleaning the probe tips?
    Thanks,
    Rick

  2. #2
    Join Date
    Jun 2011
    Posts
    14
    you can use actual ice machine cleaner, but i always use a piece of sandcloth. lets you get any mineral deposits off it get a nice clean surface.

    as for the thickness probe, when it touches water and goes to ground, it should light up a LED on the board, when the LED is on for 7 consecutive seconds, it will go into harvest. they dont really go bad to often, unless physically broke.

  3. #3
    Join Date
    Nov 2007
    Location
    central Nebraska
    Posts
    50
    Quote Originally Posted by Timmy414B View Post
    you can use actual ice machine cleaner, but i always use a piece of sandcloth. lets you get any mineral deposits off it get a nice clean surface.

    as for the thickness probe, when it touches water and goes to ground, it should light up a LED on the board, when the LED is on for 7 consecutive seconds, it will go into harvest. they dont really go bad to often, unless physically broke.
    thanks.
    Rick

  4. #4
    Join Date
    Feb 2006
    Location
    USA
    Posts
    4,381
    Quote Originally Posted by raharra View Post
    Disconnecting the probe wires from the mother-board, should the resistance of the probes change from very high (not touching any ice) to zero (contacting the ice)
    its not actually designed to contact the ice ... the water flowing between the ice & probe is what the probe is intended to sense .... a good, clean probe shouldn't give u any resistance from point that contacts water to end that connects to board .. measuring while disconnected

  5. #5
    Join Date
    Jun 2009
    Location
    DFW, TX
    Posts
    673
    I would definitely not recommend sandcloth on a sensor probe... The probe has to be perfectly smooth or water will want to stick to it, and this will cause scale to build up quickly in the scratches as well. We actually have had to replace probes that were cleaned too aggressively on the white plastic as well as it will hold water too.

    The ice sensor probe does not sense continuity to ground, it senses capacitance. That's why you can touch the thing with water on your hand and not touch the machine at all and it will still light up the board.

  6. #6
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,370
    Quote Originally Posted by trippintl0 View Post
    ...The ice sensor probe does not sense continuity to ground, it senses capacitance. That's why you can touch the thing with water on your hand and not touch the machine at all and it will still light up the board.
    That's correct. Here's a link to a past thread on the subject:

    http://hvac-talk.com/vbb/showthread.php?t=57042

    As I understand it, the ice thickness probe can be likened to a radio antenna. This "antenna" becomes part of a balanced R/C bridge circuit set up by the control board. If the water flowing over the ice touches it (or if you touch it) the capacitance value of the "antenna" changes and is sensed by the board.

    I'm not sure this explanation is 100% technically accurate by an electronics tech's standards, but I believe it's pretty close.

  7. #7
    Join Date
    Jun 2006
    Posts
    1,105
    Quote Originally Posted by icemeister View Post

    I'm not sure this explanation is 100% technically accurate by an electronics tech's standards, but I believe it's pretty close.

    As a general class ham radio operator with a bit of antenna building experience under my belt I would give it an A-

    Use more ten foot word you get the whole A

  8. #8
    Join Date
    Feb 2006
    Location
    USA
    Posts
    4,381
    well now we have the indigo, which measures sound lol .. a specific sound that a perfect sheet of ice makes which causes harvest initiation. ive seen a working unit in person .. pretty sweet stuff

  9. #9
    Join Date
    Jul 2000
    Location
    Guayaquil EC
    Posts
    10,370
    Quote Originally Posted by idontgetit View Post
    As a general class ham radio operator with a bit of antenna building experience under my belt I would give it an A-

    Use more ten foot word you get the whole A
    Instead of calling it an antenna, how about if I were to describe it as a capacitative touch switch?

    Would that promote me from an A- to an A whole?

  10. #10
    Quote Originally Posted by hvac wiz 33 View Post
    well now we have the indigo, which measures sound lol .. a specific sound that a perfect sheet of ice makes which causes harvest initiation. ive seen a working unit in person .. pretty sweet stuff
    A sonic transponder based on density.......

    From the military to ice making,it took awhile.
    FEN

  11. #11
    Join Date
    Jun 2011
    Posts
    14
    didnt mean to mislead by saying it went to ground, didnt know it was based on capacitence. best part about this trade, ALWAYS LEARNING. thanks for the lesson guys

  12. #12
    Join Date
    Jun 2006
    Posts
    1,105
    Quote Originally Posted by Timmy414B View Post
    didnt mean to mislead by saying it went to ground, didnt know it was based on capacitence. best part about this trade, ALWAYS LEARNING. thanks for the lesson guys
    Don't worry on it for a second hotshot (reference to nickname, not an insult, my past makes it hard to define sometimes) from a purely factual viewpoint, that change in capacitance is due indeed to an alteration in the "antenna's" ground plane shorting it and changing the standing wave resistance is exactly what triggers the response!

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