Plugging in Chassis fan from PSU causes no boot

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fluffyvonmittens

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Sep 18, 2015
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Hi all, long time reader, first time poster.

I just got a Cooler Master HAF X case, and am currently trying to transfer everything over from my old case.

When I plug all the fans into the chained molex connectors from the PSU without connecting the chassis fan connector to the motherboard, it starts up with all the fans, drives, CPU fan, motherboard light, etc. If I turn everything off and plug in the chassis fan connector, it acts like it wants to start up but fails to.

Also worth mentioning I haven't even plugged in the graphics card yet. I plan on using an GeForce GTX 960

Any ideas? Is it a big deal if I don't have my fans plugged into the motherboard?

Components are:

  • StarTech.com ATX2PW630 Pro PSU
    Asus P8 H67-M Pro/CSM MoBo
    Intel i5 2500 Sandy Bridge
    7200 RPM HDD
    SSD
    8GB DDR3 1600 RAM

Please let me know if there's any more info I can provide.
 
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If this is a smallish 4-pin female connector on the end of the 4 wires that also has the larger common 4-pin Molex power connectors, then definitely DO NOT PLUG THIS INTO ANYTHING! It is a power connector for the common 3½" floppy disk drive that most people no longer have. (The larger connectors originally were used, among other things, for the older and larger 5¼" floppy drives.) Plugging this into a mobo fan port does two things: it probably shorts out at least one of the lines in this set, which is why nothing works when you do that. AND it could cause permanent damage to the mobo, at least to that fan port, by supplying it with voltages it should never have.

This is exactly what I suspected, and that's why I asked the question...
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Paperdoc

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Oct 19, 2006
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What do you mean by "the chassis fan connector"? If all of your case ventilation fans are powered from a 4-pin Molex output from the PSU directly, then there is NO connection to be made to any mobo CHA_FAN port. You probably do have the cooling system for your CPU connected to the mobo's CPU_FAN port, and so you should.

So, are you plugging something in to a mobo CHA_FAN port? What is this connector - where does it come from and what does it look like? My worry is that you may be plugging something like a PSU power output into a mobo fan port, which could cause damage.
 
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fluffyvonmittens

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Sep 18, 2015
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There is a 4 pin female connector at the end of the molex cord coming from the PSU, so I assumed that was supposed to be plugged into the CHA_FAN 4 pin slot on the MoBo after you had connected all the fans to the molex.

The specs for the PSU say its a LP4 (4 pin; Molex Large Drive Power) Female if that helps
 
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fluffyvonmittens

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Sep 18, 2015
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I should have the latest BIOS, I tried to update everything before I did the transfer. The 24 and 8 pin power plugs are in there pretty snug as well.
 
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Paperdoc

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If this is a smallish 4-pin female connector on the end of the 4 wires that also has the larger common 4-pin Molex power connectors, then definitely DO NOT PLUG THIS INTO ANYTHING! It is a power connector for the common 3½" floppy disk drive that most people no longer have. (The larger connectors originally were used, among other things, for the older and larger 5¼" floppy drives.) Plugging this into a mobo fan port does two things: it probably shorts out at least one of the lines in this set, which is why nothing works when you do that. AND it could cause permanent damage to the mobo, at least to that fan port, by supplying it with voltages it should never have.

This is exactly what I suspected, and that's why I asked the question. When I read the PSU specs, I could not find any indication that its wires had one of these connectors among its outputs. In fact, you report that the specs say it is a "LP4 (4 pin; Molex Large Drive Power) Female", and I would not have thought it is really a "Large Drive" connector, so I did not recognize that to mean a power plug for a 3½" floppy drive.

For future reference, power for the fan ports on a mobo all are drawn from the already-connected main power lines into the mobo. You do NOT need to connect extra leads to get power to mobo fan ports. In your situation, the case itself came with a different style of fan designed to be powered directly from the PSU and with no control or monitoring of them by the mobo.
 
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