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Ice Maker Troubleshooting Tips

Practical Ice Maker Troubleshooting Tips

May 29, 2006

Ice Maker Troubleshooting Is Easier If You Take It One Step at a Time


Ice maker troubleshooting is always easier when you have the service manual for the machine. Since you're already online,

why not visit the ice machine manufacturer's Website and get the service manual for your machine?

You'll find Manitowoc service manuals at, Ice-O-Matic manuals at, Scotsman manuals at, and Hoshizaki service information at

The service manual provides crucial information about the ice machine refrigeration system and electrical controls, so

there's no reason to hesitate about breaking it open during service calls.

If the customer asks what you're reading, show him or her the steps in the manual, and explain that following the factory recommended procedure step by step helps make sure you don't miss anything, helps you identify the problem quickly, and helps get the repair finished efficiently, which reduces labor costs.

If you can't get the manual, all of the newer machines I've worked on have had a good set of explanations somewhere,

on the front cover, or in the control panel area, about what the indicator lights mean with regard to what part of the

operational cycle the machine is in, or what error code is being displayed.

If the indicator lights are working, and if you can find the legend that explains what they mean, they'll at least point you in the direction of what part of the machine is malfunctioning.

If your ice maker troubleshooting call is for a machine that isn't running at all, be sure to ask the owner or operator what

type of problem they might have been having with the machine before it stopped, then check the disconnect or outlet for


If there's no power at the disconnect or outlet, check the breaker or fuse (or fuses). If the breaker tripped or a fuse blew,

you'll have to use an ohmmeter and check the wiring and electrical components for a ground or short.

If you find a failed part, good job! Replace the part, inspect the rest of the machine to see if it's actually in good enough condition to run, verify that the power supplied to the machine is correct, then give it a test run.

Otherwise, if there's power at the disconnect but it was turned off, or if the machine was unplugged, ask the owner why.

If the machine was disconnected because it just wasn't running right, the next step of this ice maker troubleshooting call

will be to open the panels up and do a quick, thorough visual inspection.


You need to verify that the water supply to the machine is good, and you should also inspect the water distribution

components in the machine. If they're plugged with scale build up, the machine should be descaled, but make sure the

machine at least runs and starts freezing normally first.

If there are major problems with the compressor, metering device, controls, etc., and the machine is old enough that the

owner wants to replace it instead of paying for major repairs on an old machine, the descaling procedure might turn out

to be a waste of time.

You'll also want to take a close look at the evaporator plate. If the plating is severely discolored, or if you see a lot of

copper color showing through, the plating might be worn off to the point where ice won't drop off the evaporator during harvest. You also want to be sure there's no scale build up on the evaporator.

Check the condenser and make sure it's clean, make sure the condenser fan blade turns, and verify that nothing is

interfering with the airflow through the condenser. If it's a water-cooled condenser, verify that there is water pressure

available to flow through the condenser when the unit runs.

Attach your gauges and make sure there's pressure in the machine; and if you can, verify that it's the correct refrigerant.

If there's nothing else visibly wrong with the machine, turn on the power and verify that it is the correct voltage for the

machine. If there are solid state controls, see if there are any error code indications, and note down what they are. We'll go over possible problems and their causes shortly.

By this stage of any ice maker troubleshooting call you will have verified that the water and power supplied to the machine

are correct, that the condenser is clean and the fan is good. If it's a water-cooled condenser, you'll have verified that there's water available to flow through the condenser, and you'll have verified that the evaporator plate and water distribution components are clean and scale free.

If there are no error indications, or if the machine doesn't have solid state controls, turn the machine on to “ice,” and see

if it will run.

Keep in mind that different makes of ice makers start out differently. Hoshizaki units start by defrosting until the suction line thermistor warms up; Manitowoc’s start a couple of different ways, depending on the type of machine; and Ice-O-Matic’s

also start a couple of different ways, depending on the type of machine. So give the machine a couple of minutes to cycle

into its full freeze mode.

If your ice maker troubleshooting call is for a Manitowoc unit, and the water pump runs but the compressor doesn't run,

wait at least 10 minutes to see if it drains, re-fills, and starts rinsing again.

If it does, someone switched it to “clean,” and it won't cycle into “freeze” until it finishes the complete clean cycle.

If your ice maker troubleshooting call is for a Hoshizaki unit, pay close attention to the strength of the water flow during

the fill cycle when it starts up. These units require a strong water flow for optimum harvest efficiency, so if flow looks

weak, check the pipe size, filter, inlet screen, and distribution nozzles.


The rest of this article will cover common ice machine problems, and what symptoms to look for during your ice maker troubleshooting calls.

First, check the cuber and bin drains for steady running water. If you see this, the dump valve might be leaking, the fill

solenoid or float valve might be leaking, the drain siphon pipe might be loose or adjusted incorrectly, or the sump pan or

the machine might not be level. This will cause long harvest cycles, can trip the solid state controls on “long cycle time”

errors, and will increase the cost of making the ice.

If there are no water overflow problems, let's move on to other possibilities.

If your ice maker troubleshooting call is for a machine that immediately trips off on high pressure, put your gauges on and

verify that the pressures are actually high and that the safety hasn't failed.

If the pressures stay normal but the high pressure safety opens, the safety has failed and you need to replace it. If the

pressures are high, verify that there are no isolation or service valves closed on the high side of the system, double-check

the condenser coil to see if it's plugged, check to be sure the condenser fan is running and that it's the right size and turns in

the right direction, and make sure no other appliances are blowing hot air directly into the condenser coil.

If this ice maker troubleshooting call is for a water-cooled machine, verify that you have water flow and that it's not hot

water, make sure the head pressure regulating valve hasn't gone out of adjustment or totally failed, and if you can,

disconnect the water lines and inspect the inside of the condenser for scale or dirt buildup.

If there are no mechanical problems that would cause high pressures, it's possible the system is overcharged or

contaminated with noncondensibles.

To check for noncondensibles, leave the machine off for a few minutes so pressures will equalize. Check your pressures,

and check the temperatures of the evaporator plate and condenser coil. If your saturated temperatures aren't equivalent to

these pressures, it's very likely that the system is contaminated. You'll need to recover the charge, replace the drier,

evacuate the system, and weigh in the factory specified charge.

If the saturated temperatures are equivalent to the evaporator plate and condenser coil temperatures, and you suspect the system is simply overcharged, it's still a good idea to recover the charge, replace the drier, pull a vacuum to 500 microns,

then weigh in the factory specified charge.

You don't know who worked on the machine before you did, so you'll want to be sure that you don't leave the machine

running with an overcharged and possibly contaminated system.

OK, what about an ice maker troubleshooting call where the machine trips off on the low pressure cutout instead of the

high pressure safety?

Once again, check the pressures to be sure the suction pressure is actually low enough to trip the cutout. If the cutout

opens but the suction pressure hasn't dropped to the cutout point, the cutout has failed and should be replaced.

If the suction pressure is lower than normal and you also have low discharge pressure, suspect a low charge and check

for a leak. If you find a leak, make the appropriate repairs.

If you don't find a leak during this stage of the call, charge in two to four ounces of refrigerant to see if your suction

pressure increases. On large machines you may need to charge in a little more to see an increase in suction pressure.

If suction pressure and discharge pressure increase, it's very likely an undercharge; so you need to find out how the

charge was lost if possible, make the appropriate repairs, then charge in the factory specified amount of refrigerant.

If you suspect a leak and absolutely can't find it, charge in enough refrigerant to get the machine to make ice, charge in the correct amount of fluorescent leak detection dye, leave the machine running and making ice, and make plans to come

back and find the leak in a day or two. Return in a couple of days and, using an ultraviolet light, you should be able to

locate the leak. Make the appropriate repairs, and get the machine up and running.

What about a similar ice maker troubleshooting call with the machine tripping off on low pressure, or running with low

suction pressure, but you don't find a leak, and when you charge in refrigerant, the pressures don't rise?

First, check for a restricted drier or liquid line. If the drier is restricted, the outlet will be several degrees cooler that the

inlet, and the drier itself might even be sweating or frosting. If the liquid line is restricted, you might see frost or

condensation at the location of the restriction, and the outlet side of the restriction will be cooler than the inlet side.

If the drier and liquid line aren't restricted, check for a restricted or failed metering device. If the metering device is a

capillary tube, you might have to strip off some insulation, but if it's restricted you'll see a spot of frost at the restriction.

If the metering device is a TXV, and if you're sure the machine is fully charged and the evaporator plate is only freezing

about half way or maybe even less, then the TXV has failed.

Manitowoc recommends the following test as one step in the overall ice maker troubleshooting process:

·  After five minutes of the freeze cycle, measure the temperature of the inlet and outlet copper lines of the evaporator.

·  If the temperatures are not within 5° of each other, the TXV has failed.

·  For a double evaporator machine, measure the temperatures of the TXV outlet lines as close to the TXVs as possible.

·  If the temperatures are within 5° of each other, both TXVs are good.

·  If the temperatures aren't within 5° of each other, the TXV with the higher outlet temperature has failed.

Keep in mind, this is only one step in the overall ice maker troubleshooting procedure.


The next ice maker troubleshooting call we'll discuss will be a machine that's running, but takes too long to make ice, and is possibly tripping off on “long freeze cycle.”

You should have already verified that the dump valve, fill solenoid, and float valve aren't leaking, that the drain pipe isn't

loose or adjusted incorrectly, and that the sump pan and machine are level.

If there's no water flow problem, check the temperature of the defrost/hot gas solenoid about five minutes after the freeze

cycle starts. The inlet will be hot, but the body and outlet should be cool enough to hold. If the body and outlet are too

hot to hold, it's probably leaking, which will increase freeze cycle times.

During your ice maker troubleshooting calls you should keep an eye on your gauges, and take notes on what's happening.

Are pressures normal? If you have a high discharge pressure, check the condenser, and check for noncondensibles.

What's happening with the suction pressure? A few minutes after starting the freeze cycle, the suction pressure and head pressure should both start gradually dropping until the machine harvests.

If pressures start out normal on this call, and the machine starts making ice with a good fill pattern on the evaporator, but suction pressure doesn't drop and the ice takes way too long to build up, it's possible that the TXV has failed and no

longer responds to superheat changes. Verify that the bulb is strapped securely to the suction line, and that the contact

between them is clean. Use the TXV troubleshooting method described earlier in this article.

If you replace the TXV, make sure the replacement is an exact match for the capacity and operating range of the machine.

I'd recommend using factory replacement parts.

Let's say we're on this ice maker troubleshooting call and there's no water flow problem, discharge pressures aren't too

high, it doesn't look like the TXV has failed, and the pressures look very close to normal.

What does the ice pattern on the evaporator look like? Is the ice thickness good all the way up the evaporator? Or is the

ice thin on the last few rows of the plate?

If the ice is noticeably thinner on the last few rows of the evaporator, and if the suction and discharge pressures are slightly lower than normal, check for a low charge.

Charge in two to four ounces of refrigerant and see if the ice now builds the rest of the way up the evaporator. If it does,

the problem was a low charge, which can cause long cycle times. Find the leak and make the appropriate repairs.

Other possible causes of long cycle times are hot supply water, hot condenser water, an air cooled condenser recirculating

its own air, ice thickness control set too thick or failed, too much water flowing into the sump, failed harvest pressure

regulating valve, inefficient compressor, or someone might have installed the wrong compressor or TXV.



What about an ice maker troubleshooting call where the machine makes ice, but it won't drop off the evaporator during harvest? You should have already verified that there's no scale build up on the evaporator, and that the plating looks good.

On this type of call the service manual will be a lot of help. It will tell you what the pressures should be during both the

freeze and harvest cycles.

If your pressures are good during the freeze cycle, but not as high as the factory specifies during harvest, check for a low charge, restricted hot gas solenoid, or inefficient compressor. Once again, the manual for your specific machine will give

you more detailed guidance on how to troubleshoot it.

If harvest pressures are normal during this call, but the ice doesn't drop off the plate, the evaporator plate is clean and scale free, and the machine is level, there's a strong possibility the plating has worn off the evaporator, which will make the ice

stick even during harvest.

Pull the curtain off and take a close look at the ice slab during harvest. If you can look through the ice slab and see the

water running down between the slab and evaporator, but the ice simply sticks on the evaporator and doesn't drop off, the plating is gone, and the evaporator has to be replaced.

On a Hoshizaki ice maker, you don't have to worry about plating because they have all stainless evaporators. But if ice

seems to drop off the evaporator too slowly, and harvest pressures are good, check for strong water flow into the machine during harvest, and make sure the water distribution nozzles are clear.

There are separate sets of nozzles in some Hoshizaki machines, so during the harvest cycle be sure there's good water flow through the nozzles that fill down between the plates. This water flow helps warm up the plate during harvest.


Let's try an ice maker troubleshooting call where there's good power to the machine, and overall it looks in good enough condition to run, but when you turn it on to make ice, nothing happens.

Again, check for any LED error indicators, and troubleshoot according to the schematic and legend on the machine.

·  Check for a high pressure switch that needs to be manually reset. If you find one tripped, use the method described

earlier in this article to determine why it tripped.

·  Check the manual on-off toggle.

·  Check the bin switch.

It could be a magnetic switch on the water curtain, a thermal element that opens when ice in the bin cools it down to its set point, an infrared beam and sensor assembly, a push-rod that the curtain activates, or a lever that the curtain activates.

If you find that there's no water in the sump on this call, and if it's a machine that cycles on a float switch or water level

sensor, verify that the fill solenoid is energized. If the top of the armature doesn't feel magnetized, check for voltage at the

leads to the coil. If the voltage to the coil is correct but it isn't energizing, the coil has failed and needs to be replaced.

Let's say that on this call the fill solenoid is energizing, but no water is getting into the machine. Crack open the inlet fitting

to the fill solenoid to see if there's good pressure available, then crack open the outlet. If there's water pressure on the inlet

side but not on the outlet side, the solenoid is restricted and needs to be cleaned or replaced. If there's no pressure even

on the inlet side, you need to check the water supply to the machine. After you take care of the water problem, the sump should fill to the point where it satisfies the float switch or level sensor, then the machine should cycle into freeze.

If the machine doesn't cycle into freeze when the float switch lifts or when the water reaches the level sensor, you'll need to check the operation of the float switch assembly or level sensor. The problem might be dirt, sludge, or scale buildup, or

the part has failed.

Whether or not the machine cycles into freeze at this stage of the call, keep an eye on the fill water flow and make sure it

stops. Some machines will continue to fill a little more water after the machine cycles into freeze, but if the machine

continues filling to the point where you have a steady drain out of the sump, check the fill solenoid. If it's de-energized

but fill water

is still flowing, it's probably being held open by some debris, and you'll need to disassemble the valve and clean it out.

Continuing this call, if you didn't find any of the previous possible problems, check the wiring and connections in the

machine for a loose connection or broken wire, and check for a blown control fuse or a failed relay, contactor, or time


You might even have to trace through the controls wire by wire to see if a control wire is connected to the wrong place.

This would be another call where the service manual for the machine will save you a lot of time and frustration.



What about an ice maker troubleshooting call where the machine turns on, the water pump runs, and water is flowing

over the evaporator, but the compressor doesn't run?

First, if you hear the compressor humming and tripping off on its overload, turn the power off. Remove the leads from the compressor terminals, and ohm out the compressor windings. If the windings ohm out OK with no indications to ground,

the next thing to do is make sure the leads aren't grounded or shorted to anything, then turn on power and verify that

there's good power at the compressor leads. If there's good power at the leads, replace the start relay, start capacitor, run capacitor, and external overload (if installed), reconnect the leads to the compressor, and turn the machine on and see if the compressor will run.

At this point in the call, if you have good voltage at the compressor, and new start components, but the compressor simply won't run, but just hums and trips the overload, you can be pretty sure the compressor is locked up and has to be replaced.

Otherwise, if you're on a call where the compressor doesn't run but it's not humming and tripping off:

·  Verify that the contactor has pulled in.

·  If it hasn't, check the voltage at the coil.

·  If you have control voltage at the coil but it doesn't pull in, the contactor has failed and needs to be replaced.

·  If you don't have control voltage at the coil, you need to trace back through the circuit to see if there's an open safety,

broken or loose wire or terminal connection, or a failed control relay.

At this stage of the call, if the contactor has pulled in, check the voltage on both the line side and load side, and check

across the contacts to see if one set has failed and isn't conducting. If you have good voltage on the load side of the

contactor, check the voltage at the compressor terminals and start relay.

If you don't have good voltage at the compressor terminals and start relay, look for a broken or loose wire or terminal connection. If you have good voltage at the start relay and compressor terminals, ohm out the compressor windings (and external overload if installed).

By this stage of the call, if the compressor is three phase, or single phase with a potential start relay arrangement, you'll

have already found the failed part.

If this is a small compressor with a current relay and external overload, and the windings ohm out OK with no indications to ground, you'll probably find that either the overload has failed open, or the current relay has failed. If you replace the

failed part, the compressor will probably run, and I'd recommend replacing all three parts.

That about covers the most common ice maker troubleshooting calls.

Mike Taitano is a technician with 20 years of experience troubleshooting, repairing, and maintaining air

conditioning and refrigeration equipment. He also operates

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Publication date: 05/29/2006