The splitters only have all 4 pins on one of the male connectors, the rest have 3, this is normal for these cables. The motherboard can only take fan speed from 1 fan, so the cable for monitoring fan speed is only on 1 connector.
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PC Fan Splitter 4 Pin PWM Fan Splitter Cable PC Case Fan Header Splitter for Computer 4 Pin or 3 Pin Cooling Fan
Aliexpress UK
IDE(4Pin) is used to connect the fan cable, and the fan connector adopts 3+1connector, which can connect the small 3Pon and 4Pin fans. Our warranty covers your machine against technical defects that develop within the warranty period defined.
eBay
SATA Cooler Fan Adapter Cable，15 Pin SATA to 4 x 3 pin / 4 pin Fan Splitter Cable,15 Pin Male SATA to 3 Pin or 4 Pin Computer
Aliexpress UK
Product Function : Allows five ARGB PC fans to share a single ARGB header. Connector Type : 3-Pin ARGB connector for PC case fan lighting synchronization. Conductor Material : Tinned Copper. Conductor Specification : 17 0.12TS.
eBay
4 Pin Y Splitter Cable 4 Pin PWM Female To 3/4 Pin Motherboard CPU Fan PC Case Fan Extension Adapter Cable Fan Cooling Accessory
Aliexpress UK
Connect NZXT AER, AER 2, F120 RGB, and HUE Series fans directly to a standard ARGB motherboard with our 3-Pin to NZXT Fan Splitter Adapter. This 30/30cm + 10/10cm UL 1007 24AWG cable supports up to 3 fans, eliminating the need for a controller and providing seamless ARGB daisy chain passthrough. Enjoy vibrant lighting effects without compromising on fan speed control. Compatible with NZXT AER RGB, AER 2 RGB, RGB CORE, and HUE+ / HUE 2. Upgrade your setup effortlessly and enhance your PC's aesthetic with this bespoke adapter.
eBay
TEUCER 4-Pin Splitter Cable 4 Pin 1 to 3 Way PWM Fan Splitter Cable Sleeve Extension Braided Cable Extension Fan Connector
Aliexpress UK
4 pin PWM fan cable 1 to 2 way Y splitter extension. Convenient and neater solution for running multiple fans. For more than 2 fans we have 1 to 3 & 1 to 4 way cables and 5 port hubs also listed. The extension cable is braided sleeved and heat shrunk at the connectors.
eBay
SATA to 3 Pin / 4 Pin Fan Adapter 15 Pin SATA to 12V PC Case Fan Splitter Extension Power Cable Adapter
Aliexpress UK
3 PIN PC FAN POWER SPLITTER. 1 x 3 pin connector - female. 2 x 3 pin connector - male. This cable will extend the length of an internal power cable. to stop your beloved PC from overheating!
eBay
PWM Fan Splitter 4pin Adapter Cable 1 To 1 2 3 4 Computer CPU Fan Splitter PC Fan Extension Power Cable Fan Cooling Y Splitter
Aliexpress UK
Conductor Material: tin plated copper. Conductor Specifications: 11 0.12TS. Connector: 1 x 4pin motherboard connector, 3 x 4pin/3pin fan connector(This universal connector could use to 3Pin and 4Pin ).
eBay
TEUCER 4 Pin 1/2/3/4 Motherboard CPU Fan PC Case Fan Extension Adapter Cable PWM Female to 3/4 Pin Splitter Cable
Aliexpress UK
1 x New Fan 4pin to 3 x 4pin/3pin extender cable 4pin to 1 Ways Y Splitter Cable 30cm/11.8". The wires are 30cm sleeved in black braiding with a 4pin female connector at 1 end and splits to 3 4pin male connectors at the other.
eBay
1 To 10 PWM & ARGB Hub Splitter SATA Powered 4 Pin PWM 3 Pin Addressable ARGB Adapter ARGB Controller Splitter for PC Case Fan
Aliexpress UK