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CMI / IBM Fan Unit with (5) 4.75 Inch, 12 VDC 3 Wire Brushless Axial Muffin Fans with Tachometer Outputs NOS

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MPN:
88G4178 / D44261A
Condition:
New
Shipping:
$28.00 (Fixed Shipping Cost)
  • NOS 1997 set of 5 IBM-style 12VDC 3-wire tachometer muffin fans (88G4178 / D44261A, CMI). Vintage 120mm axial cooling fans – ideal for servers, PCs, DIY projects with RPM monitoring.
  • NOS 1997 set of 5 IBM-style 12VDC 3-wire tachometer muffin fans (88G4178 / D44261A, CMI). Vintage 120mm axial cooling fans – ideal for servers, PCs, DIY projects with RPM monitoring.
  • NOS 1997 set of 5 IBM-style 12VDC 3-wire tachometer muffin fans (88G4178 / D44261A, CMI). Vintage 120mm axial cooling fans – ideal for servers, PCs, DIY projects with RPM monitoring.
$39.99
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Description

CMI / IBM Fan Unit with (5) 4.75 Inch, 12 VDC 3 Wire Brushless Axial Muffin Fans with Tachometer Outputs NOS

  This fan unit was purchased new by me some time ago. It has never been in service but has been sitting on the shelf for several years.

  While it has Tachometer outputs, you can simply two of the wires in the plug to run the fans at full speed. I have wired up a power cord with the two proper size pins to run them this way.

  They run quiet and push a good amount or air.

 

(New Old Stock) 1997 12V DC 3-wire brushless axial muffin fans with tachometer output, originally from IBM equipment (likely server or PSU cooling assemblies). The part numbers 88G4178 and D44261A link to IBM dual-fan setups (e.g., similar to 96G4180 assemblies), where individual fans were used. CMI is the manufacturer.
 
 
Key Specs (Typical for This IBM-Style 120mm-Class 3-Wire Fan)
  • Voltage: 12 VDC nominal.
  • Wiring: 3-wire (Red: +12V, Black: GND, Yellow/White: Tachometer output – open-collector pulses for RPM monitoring; usually 2 pulses per revolution).
  • Type: Brushless DC axial muffin fan.
  • Size: Standard ~120 x 120 mm frame (likely 25mm or 38mm thick – measure to confirm; common for rack/server use).
  • Date Code: 10/08/97 (genuine old stock).
  • Performance: Typical for similar units: 50–150+ CFM range, moderate noise, reliable bearings (ball or sleeve). Current draw often 0.2–0.5A+ per fan depending on speed.
  • Applications: Server cooling, electronics enclosures, DIY projects, monitoring via Arduino/motherboard tach headers (pull-up resistor may be needed on tach line).
Wire Function Breakdown
  • Positive Power Wire (+12 VDC): Delivers the constant 12-volt DC power required to spin the motor.
  • Negative/Ground Wire (GND): Completes the electrical circuit.
  • Tachometer (TACH) / Sensor Wire: Transmits a "Locked Rotor" alarm or a pulse signal (usually 2 pulses per revolution) back to a motherboard or controller to monitor the fan's actual RPM (Revolutions Per Minute).
     
 
Common Wire Color Codes
Because color standards can vary by manufacturer, you will typically see one of two color schemes:
Guangdong Chungfo Electronic Technology Co., Ltd
 
Wire Function Standard Scheme Alternative Scheme
+12V Positive Red Yellow
Ground (GND) Black Black
Tachometer (RPM) Yellow or White Green or Blue
 
How Speed is Controlled
Unlike 4-wire fans—which use a dedicated fourth wire to receive digital Pulse Width Modulation (PWM) signals—a 3-wire fan's speed is altered by varying the DC voltage on the positive line (voltage scaling) or by cycling the main power line itself. If you leave the third tachometer wire completely disconnected, the fan will simply run safely at 100% full speed.
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