Manitowic Harvest Issues - Senses harvest too soon

[clman_old]

Model#: QW1305W

Was making ice too thick then too thin alternately without any adjustments. It needed cleaning so we cleaned it hoping that the slime on the bridge / thickness sensor might be causing it. Didn't solve the problem. The sensor was changed about 5 months ago because it was going into harvest too soon. The harvest light, then and now, would come on with the sensor detached from the spray tube and moved away from the grid several feet. Touching the sensor, while removed and not touching anything else, would cause it to trip harvest. I don't think it's supposed to be that sensitive. Disconnecting the sensor connector from the board was / is the only way to stop it from going into harvest. Touching the terminal on the board, without touching anything else, also causes it to switch into harvest.

 

I think it's the sensing circuit in the control board. The troubleshooting chart in the manual says the same. I know experience is everything. Anybody dealt with this before?

[jumptrout]

Your ice thickness control is bad if the machine continues in the freeze cycle when unplugged from terminal 1C on the board.

When unplugged,if the harvest light comes on the board is bad.

The ice probe operates through GROUND circuit.

Make certain the machine is well grounded as well as the ground circuit to the board.

When you touch the 1C terminal you are most likely causing a Grounded condition.

Manitowoc makes several ITP's.

The wrong probe will not work correctly.

Bridge adjustment and water flow must be correct.

Splashing water is not good.

[clman_old]

The harvest light goes off when the sensor is unplugged. The light is off for the 6 min freeze lock period, or 3-5 min if freeze lock is bypassed, then the harvest light comes on. It will stay on if the sensor is raised or moved away form the grid.

 

I watched the water flow very closely and witnessed no water coming into direct contact with the probe. The probe did get an occasional small splash from the water breaking on the adjustment screw but it has to be a constant 10 sec reading before the board decides it's a good measurement. And it still does it when dried off.

 

A ground path through my body would be minute. If it's functioning correctly, that would indicate to me that the amount of ground the board is watching for is also minute. That would seem too sensitive to me. When previously malfunctioning I could just hold the probe assmy by the plastic of the probe and it would sense harvest.

 

The probe was purchased from the local Manitowoc dealer and appears to be the exact same as the original one. It also worked without issues for several months after being changed.

 

I know the symptoms point to the probe but it's hard to believe that it's bad again. Especially considering how simply made it is. I don't think the wire from the probe is a resistor wire ( I checked it for resistance and got infinity ) and, so far as I can tell, the probe it self is just the metal plate attached to the wire.

 

Honestly I can't see how the probe could ever go bad unless the plastic cracked or the wire came off the stainless strip. Not sensing correctly because of being dirty would make sense - but it's clean.

 

I'm thinking that with these symptoms and a correctly working board it would be the probe. But what if the board is reading a less than required - very low amount of ground as enough to indicate that the ice is the correct thickness?

 

I am going back today to check ground. I'm also wondering if voltage leaking to ground somewhere in the building might screw up the ground reading to the board.

[jumptrout]

The manual as well as Manitowoc Techl8ine will tell you that...........if the probe is unplugged and the machine stays in freeze mode the probe is bad.

With the probe unplugged and the machine enters harvest the board is bad.

The Manitowoc site also has a *WARNING* posted to be wary of counterfeit parts on the recent market.

[clman_old]

I went back today and it's working normally - so far, Crazy. But I hear ya. The probe!