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Error code reference

Sub-Zero Refrigerator Error Code 50 U 87

Water flow meter did not detect flow.

Sub-Zero codesSub-Zero refrigerator codes

Water flow meter did not detect flow.

First step from the service manual

Verify water pressure, water flow, and that flow meter is not blocked or dirty.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Step-by-step tests with expected resistance, voltage, and continuity values
  • Wiring diagram references and connector pinouts from the OEM service manual
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What 50 U 87 means on a Sub-Zero refrigerator

Error code 50 U 87 on a Sub-Zero refrigerator indicates that the water flow meter failed to detect any water movement during an ice maker or dispenser fill cycle. The flow meter is a small inline sensor positioned in the water supply line that monitors actual water passage by counting pulses generated by a spinning impeller or paddle wheel as water flows through it. When the control board initiates a fill command and receives no pulse signal from the flow meter within the expected time window, it logs this fault code and halts the fill cycle to prevent overflow or dry operation.

The most common root cause is insufficient water pressure at the inlet. Sub-Zero refrigerators require a minimum supply pressure, and if household pressure is too low or a shutoff valve is partially closed, the flow meter impeller may not spin enough to register flow. Blockages within the flow meter itself, such as mineral scale buildup or debris from the supply line, can also physically obstruct the impeller and prevent any reading even when water pressure is adequate.

A failed or dirty flow meter, a kinked water supply line, a clogged water inlet valve screen, or a defective water inlet valve solenoid can all produce the same symptom. The diagnostic process should start by confirming adequate water pressure and unobstructed flow at the supply line before condemning the flow meter or inlet valve as failed components.

Source: manufacturer service documentation.

Common causes of 50 U 87

  1. 01

    Low or interrupted water supply pressure

    Wiring / connection

    If the household supply pressure is too low or the shutoff valve behind the refrigerator is partially closed, there may not be enough force to push water through the system and trigger the flow meter. Check that the supply valve is fully open and verify adequate pressure at the line.

  2. 02

    Blocked or dirty flow meter

    Part replacement

    Mineral deposits, sediment, or debris can coat or jam the flow meter impeller, preventing it from spinning and registering flow even when water is present. Inspect and clean the flow meter or replace it if the impeller is physically damaged or seized.

  3. 03

    Clogged water inlet valve screen

    Wiring / connection

    The inlet valve has a small mesh filter screen that can accumulate sediment over time, restricting flow to the point where the flow meter receives no detectable water movement. Remove and clean or replace the screen to restore adequate flow.

  4. 04

    Kinked or pinched water supply line

    Wiring / connection

    A kinked line between the wall supply and the refrigerator can restrict or completely stop water flow without any fault in the refrigerator components themselves. Pull the unit forward and inspect the full length of the supply line for any bends or compression points.

  5. 05

    Failed water inlet valve solenoid

    Part replacement

    If the inlet valve solenoid does not open when commanded by the control board, no water reaches the flow meter and the fault is triggered. A failed solenoid typically requires valve replacement.

See the test procedure for each cause

Frequently asked questions about 50 U 87

What does 50 U 87 mean on a Sub-Zero refrigerator?
Error code 50 U 87 means the water flow meter did not detect any water movement during a fill cycle. The refrigerator monitors water flow with an inline sensor, and this code appears when that sensor registers zero flow after the control board commands water to run. The fault points to a supply pressure issue, a blockage, or a problem with the flow meter or inlet valve itself.
How do I fix error code 50 U 87 on my Sub-Zero refrigerator?
Start by confirming the water supply shutoff valve is fully open and that household water pressure is adequate at the refrigerator connection. Next, inspect the water supply line for kinks, check the inlet valve screen for sediment buildup, and examine the flow meter for debris or mineral scale on the impeller. If cleaning does not resolve the fault, the flow meter or water inlet valve may need to be replaced.
Is it safe to keep using my Sub-Zero refrigerator while error 50 U 87 is active?
The refrigerator itself will continue to cool normally while this code is active, so food safety is not immediately compromised. However, the ice maker and water dispenser will not function correctly until the water flow issue is resolved. Leaving the fault unaddressed for an extended period can allow ice maker components to run dry and wear prematurely.
Will resetting the refrigerator clear error code 50 U 87?
A reset may temporarily clear the displayed code, but if the underlying water flow problem has not been corrected the fault will return as soon as the refrigerator attempts another fill cycle. The code should only be considered resolved after the root cause, such as a blocked flow meter, low pressure, or a faulty inlet valve, has been diagnosed and corrected.
How much does it cost to repair a Sub-Zero refrigerator showing error 50 U 87?
Repair costs vary depending on the cause. If the fix is simply opening a shutoff valve or clearing a kinked line, there is no parts cost involved. Replacing a clogged inlet valve screen is inexpensive, typically in the range of a few dollars to around twenty dollars for the part. A new flow meter or water inlet valve assembly on a Sub-Zero unit can cost anywhere from roughly sixty to over two hundred dollars for parts alone, with additional labor costs if a technician performs the repair.

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