Can molex fans have speed adjusted?

[Kai__M]

I know that molex goes straight to the PSU, however, my situation is a little different.

I have a Noctis 450 and I'm using the included fan hub to have the fans adjust their speed based on the speed of the CPU fan.

Recently I ordered two 140mm fans for the top of the case but neglected to ensure that they used a three/four pin connector. The fans have only a molex connector. I thought that the Noctis 450 fan hub didn't require connected fans to be PWM because it adjusted speed through changing the voltage going to the fans. Can I just use some kind of molex->3-pin adapter, or will these fans not be able to have their speed adjusted at all? Hope I didn't waste my money. 🙁

 

[jrrdmchls]

I know that molex goes straight to the PSU, however, my situation is a little different.

I have a Noctis 450 and I'm using the included fan hub to have the fans adjust their speed based on the speed of the CPU fan.

Recently I ordered two 140mm fans for the top of the case but neglected to ensure that they used a three/four pin connector. The fans have only a molex connector. I thought that the Noctis 450 fan hub didn't require connected fans to be PWM because it adjusted speed through changing the voltage going to the fans. Can I just use some kind of molex->3-pin adapter, or will these fans not be able to have their speed adjusted at all? Hope I didn't waste my money. 🙁

Amazon has a number of options.

https://www.amazon.com/s/ref=nb_sb_ss_i_4_9/132-2798063-8123413?url=search-alias%3Daps&field-keywords=molex+to+3+pin&sprefix=molex+to+%2Caps%2C161&crid=3MKPUCS3CNPBJ

 

[Kai__M]

I know that molex goes straight to the PSU, however, my situation is a little different.

I have a Noctis 450 and I'm using the included fan hub to have the fans adjust their speed based on the speed of the CPU fan.

Recently I ordered two 140mm fans for the top of the case but neglected to ensure that they used a three/four pin connector. The fans have only a molex connector. I thought that the Noctis 450 fan hub didn't require connected fans to be PWM because it adjusted speed through changing the voltage going to the fans. Can I just use some kind of molex->3-pin adapter, or will these fans not be able to have their speed adjusted at all? Hope I didn't waste my money. 🙁

Amazon has a number of options.

https://www.amazon.com/s/ref=nb_sb_ss_i_4_9/132-2798063-8123413?url=search-alias%3Daps&field-keywords=molex+to+3+pin&sprefix=molex+to+%2Caps%2C161&crid=3MKPUCS3CNPBJ

Thanks! I really appreciate your response.

Although, I guess what I mean to ask is not whether an adapter exists, but whether the speed of the fan will be controllable when plugged in through an adapter. I purchased the molex version of the fans by accident, and if I buy adapters now and they don't allow me to control the speed it'll just be wasted money. 🙁

 

[Paperdoc]

The answer is yes, you can control those fans with that Hub. You are correct in understanding that it uses the PWM signal from a mobo header to create its own group of 3-pin fan ports that use Voltage Control Mode, which is the only way to control 3-pin fans. And you're right, a 2-wire fan designed for connection to a Molex PSU output is the same, excepting the missing speed signal on Pin #3.

However, you will have to do a small amount of custom modification to each fan. The adapter you wish for would have a female 4-pin Molex (4 holes in one line) on one end, and a female 3-pin fan connector (3 holes in one line) in the other end. I have never seen one like that. All the adapters I've seen (including all the ones linked by jrrdmchls above) are designed for the opposite situation - a Molex male on one end, and a 3-pin fan male on the other - so you can power a standard fan from a PSU female Molex output connector. What you'll really need to do is get two standard fan connectors (with wires already on them to make it easier). Maybe scavenge off used fans, or buy a fan extension cable. Then for each fan you'll need to replace the Molex on it with one of the fan connectors. Easiest way is to splice wires together, solder the connections and insulate.

What connections to make? A 3-pin fan connector has 3 wires: Black on Pin #1 for Ground, Red on Pin #2 for +VDC (varying voltage), and Yellow on Pin #3 for the speed signal. Your two fans do not have a speed signal coming out of them, so I expect they each have one Black wire (Ground) and one Red wire (+VDC) from the fan motor to the Molex connector. Just match Black to Black, and Red to Red. For the Yellow wire on the re-purposed fan connectors, just do NOT connect it to anything. Snip it short and ensure the end is insulated so it can't make an unwanted connection.

At the Hub, I hope you have done one small detail properly. The Hub has Port #1 white. You REALLY should plug into that port the cooler for your CPU. That port is the only one that sends back to the CPU_FAN header the speed of its fan. The CPU_FAN header does extra monitoring of the fan connected to it to ensure that the CPU chip IS getting cooled, so it is important that the fan connected to that header really is the fan that cools the CPU chip.

 

[The Paladin]

there are 3/4pins to molex adaptors you could use.

https://www.newegg.com/Product/Product.aspx?Item=9SIA9F94670675&ignorebbr=1&nm_mc=KNC-GoogleMKP-PC&cm_mmc=KNC-GoogleMKP-PC-_-pla-_-Cables+-+Internal+Power+Cables-_-9SIA9F94670675&gclid=Cj0KEQjwrYbIBRCgnY-OluOk89EBEiQAZER58onTRSAwzxcLFo4rrAjigXAyzXr0gnuRCf5FUGWYNH8aAkew8P8HAQ&gclsrc=aw.ds

 

[Paperdoc]

The problem with that adapter is that, although it has both male and female connectors for the 4-pin Molex end, the FAN connector on the other end is male. OP will be trying to plug that into a mobo MALE header, and it cannot work. That's why I said OP will need to do a bit of custom work.

 

[The Paladin]

the 4 pin male connects to motherboard, the Molex to the fan.. your done... nothing complex here.

 

[Paperdoc]

You're not catching the point. The fan connector on the end of the adapter from your link is MALE, with pins. The mobo header also is MALE, with pins. You cannot plug one into the other!

 

[The Paladin]

Oh Snap ! quite right, I missed that... here is the one he needs Power Cable Molex-Y 4 pin to 3 pin Female PC Fan Cable Adaptor
https://www.ebay.com/p/?iid=321443920061&lpid=82&&&ul_noapp=true&chn=ps

I could not find a 4 pin female fan connector, but it matters little, just set bios to run for 3 pins instead of 4 and it will do the same thing.

and yes 3 pin to board header and molex to fan.

 

[Paperdoc]

You are quite right, that adapter would do the job perfectly.

Actually, in BIOS Setup, OP needs to set the mobo header involved to use PWM Mode. That is because in this scenario he / she is not connecting those fans directly to the mobo header. OP is using a Hub supplied with the case, and the Hub requires a PWM signal to manage its own group of 3-pin (Voltage Control Mode) ports for fans.