Manitowac ice mache won't harvest

[corrinado]

I have a relatively new manitowac (2010) ice machine that makes ice and harvests for a few cycles but after a while it gets hung up and exceeds the 3.5 minute limit and goes back into freeze. I have checked refigerant charge and compressor current and they are within range. I had an issue with the bin switch so it was replaced as was the thickness switch and control board as I found a new one in the box on a shelf here at work. I have cleaned the evapoartor a half dozen times and this issue is reacurring. Anyone that has experience with this please chime in with any advice you have.

[PLEH2EREH]

I used to work on these many years ago so forgive me if my "ideas" are a lil' ol fashion.....
1}Is the ice machine/bin level
2}Does the water "if water cooled" or fan "if air cooled" turns off during harvest
3}Is the ice bridge is correct thickness
4}What brand ice machine cleaner is being used
5}Are there any nicks or rough edges or bent {squares} on the evaporator plate
6}Is water getting behind the evaporator plate during freeze cycle

[McCann]

If it has a remote condenser; This could be caused by low refrigerant on cool nights or the head master is failed and not keeping pressure high enough to maintain heat during harvest. Spray water on the remote condenser and test the head master. Head pressure should stay up.
Ice machines take so dang much time because you need to sit there and watch the cycles. Have a watch and time everything. Put you hand on the piping in different areas to feel what is happening with the hot gas valve. Watch the head pressure and suction and watch the sheet fall.
What is the model? If Q then here is a manual
http://www.manitowocice.com/docs/upl...q_model_sm.pdf

If head is not a problem during defrost, ice is even, and the ice falls off nice when you are there in about 1.5 min; I too have replaced the seemingly ok thickness probe and had this problem go away. But that was a shot in the dark, as I don't really know what was wrong with it, ha ha.
If the evaporator is getting old, I have made the ice a little thicker to help pull it off.
If the door (curtain) magnet sensor is failing, it will not know it harvested and fault also.
Be sure water flows nice, no slime hidden under the pump and all water distribution cleaned with brushes.
Ice machines are a pain.

[frostline]

I had a similar problem recently with a very large Manitowoc. It was the same deal, a few successful cycles then ice hang up on defrost then exceed time fault. turned out to be a faulty hot gas solenoid, not allowing enough hot refrigerant into the evap. Intermittent faults like that just take patience. I've been working on these things for quite a few years now and the best advice that i can give you is,.. get to know the unit, understand its full sequence of operation then just sit and watch taking note of every sound and feeling pipes etc... the fault is always obvious when you know how the thing thinks....

[LynnCD]

Frostline is right on the money, learning it's sequence of events is probably the number one way to fix any Manitowoc ice machine. If you don't know what they are, you can download the service tech handbooks for free from Manitowoc's website. These handbooks will include sequence of operations and information on how to properly diagnose, depending on your model number.