When your Manitowoc ice machine shuts down prematurely, it most likely is going off on what’s called a safety limit. On Q Series ice machines there are 2 different safety limits, that will help you diagnose the problem. To check the which safety limit is the problem, simply turn your machine from the off position to ice and count how many times the harvest light flashes. Below are what the 2 safety limits mean.
Safety Limit #1 : If the freeze time reaches 60 minutes, the control board automatically initiates a harvest cycle. If 3 consecutive 60-minute freeze cycles occur, the ice machine stops.
Safety Limit #2 : If the harvest time reaches 3.5 minutes, the control board automatically returns the ice machine to the freeze cycle. If three consecutive 3.5 minute harvest cycles occur, the ice machine stops.
Safety Limit #2 is a more common safety limit and can be caused by the ice maker simply being dirty. A dirty evaporator will hold ice and not allow it to fall until it is mostly melted away. Because there is not enough ice to force the water curtain open and break the bin switch, the machine simply thinks it never harvested.
Assuming your ice machine is clean, there are 2 other areas that are most common for shutting a Manitowoc Ice machine down on a safety limit #2. A missing magnet on the water curtain or your water curtain being broken will cause your bin switch to fail. The magnetic bin switch on a Manitowoc ice machine relies on proximity to the magnet to know when to terminate the harvest cycle. This switch will not read if it does not make proper contact with the magnet. To remedy this issue simply replace the water curtain.
Another culprit, which can also lead to intermittent problems, is a failed bin switch. The only way to properly test a magnetic bin switch is to OHM it out and look for consistency. However, it is possible for the switch to fail on say the 100th time, so if you are experiencing regular Safety Limit #2 lockouts, it might be a good idea to go ahead and eliminate the bin switch by replacing it.
Lastly, never underestimate a good cleaning. Most Manitowoc ice machine problems can be fixed without any parts, simply a good cleaning will return the ice maker back to proper operation. If you have any questions about diagnosing or replacing Manitowoc ice machine parts, ask your question below in the comment section.
Why would a machine stop harvesting after about 2 hours? Seems to be working great before that. Its been well cleaned. The ice door switch is working. Any suggestions would be appreciated.
Rob,
The ice door switch or magnetic bin switch may be working, but it may be intermittently failing. The only way to properly test a bin switch is to OHM it out and look for consistency. Furthermore, it may work fine for 100 cycles, then fail on the 101, causing a long harvest or not terminating harvest properly.
It’s pretty common and a simple fix to simply replace the bin switch. Most Manitowoc intermittent problems are caused by bin switches.
If you need more assistance, please contact us and we’ll do what we can to help diagnose. When emailing, please provide your model and serial number.
http://icemakerpartsshop.com/contact-2/
Is there any way to change the 3.5 minute harvest time before registering a fault? Our machine has been cleaned twice but still takes slightly over 3.5 minutes to drop the ice thus causing the #2 safety limit fault after 3 attempts and shuts down. The ice seems to slide off the evaporator unevenly. Could one side have some kind of blockage when the hot gas valve activates? Freeze time about 10 minutes between cycles. Cubes adjusted for medium size.
Thanks for any input.
No, there is not a way to adjust the harvest safety limit. It is possible that you are having a refrigeration problem, which would require a refrigeration tech to verify.
Please note however, that a good cleaning involves using a nonabrasive brush to scrape the scale off of the evaporator. It’s hard to see the scale build up when the evaporator is wet, let it dry out to inspect for a proper clean.
Lastly, Manitowoc’s evaporators are nickel plated, so if you start seeing a coloration like a penny, the nickel plating has worn off. This could also cause you to have harvest problems, which at that point it is time for replacement.
Man. model QD0422A. Water curtain #40-0479.3. Do you carry this one? I am having time out problems. The magnet is fairly new and the green light indicates it is working every time. Failure is intermittent as your article states. The curtain is warped, could this be the problem?
If the curtain is warped it’s possible it’s not making good contact, but not likely if the light always comes on, indicating that the bin switch is made.
First, you can fix a warped water curtain by applying heat to it(from a heat gun, hand dryer, hair dryer, etc…) and then laying out on a flat surface.
Next, make sure your machine is level, if it’s off just a bit it’ll cause the curtain to swing free.
Lastly, if you are still experiencing an intermittent problem I would recommend replacing your bin switch.
I have a manitowoc model qd0422A. The machine starts up fine but after 10-15min it shuts down without dropping a single batch. Ive cleaned the filter and the magnet on the curtain and the grid still has the nickel look.( not the penny color)
When i see small cubes of ice start to form but it never goes through the whole process. Any help or advice would be greatly appreciated!
Charlie, sounds like your ice machine might be going into harvest too soon. In harvest, without enough ice to break the bin switch, it’s shutting down on a long harvest.
I’d recommend unplugging the ice thickness control from the board and seeing if it stays in the freeze cycle longer. If it does and makes a good batch of ice, but never harvests, simply clean or replace your ice thickness control.