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Corsair Power Supply RMnnnx series Questions

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1. Should the fan in the power supply come on when the unit is plugged in with no output connections?


2. The covers on 2 new RMnnnx power supplies appear to be upside down as compared to published pictures and logic. "Logic" meaning that when installed in a 4000D case the correct way (fan pointing down towrd the bottom filter) the printing "RNnnnx" is upside down when the case is standing on its legs. Seems odd???  The covers in question are held on by 4 screws, one of which has a safety sticker.  If the cover was turned 180 degrees, then the wording would correspond to published pictures.  Anyone else notice this???

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I've been reading a lot of past power supply questions - in one, you (LeDoyen) suggested turning the PSU so that the fan was pointing into the case.  Is that the suggested corect orientation for the PSU???

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It is the correct orientation for all PSUs yes. Fan down needs to dissapear.. Fan down kills babies.. Fan down slays kittens by the dozen.

The thing is as you may have read, the heat should rise away from the components, meaning fan upwards. Otherwise the fans will start and stop constantly when under even moderate load because the PSU will remain bathing in its own heat.

Case manufacturers are just starting to catch on to that fact with vented PSU shrouds. It's odd that Corsair who manufactures both PSUs and cases took so long to do that.

And no, the fan should not come on when you start, with or without components. It will turn only if needed, either by excess heat or high load, or both.

The PSU usually does a "twitch" test of the fan, where you'll see the blade moving very briefly when you power on. that's just to test that the fan isn't blocked, then it stays off until needed.

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I've been reading a lot of past power supply questions - in one, you (LeDoyen) suggested turning the PSU so that the fan was pointing into the case.  Is that the suggested corect orientation for the PSU???

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Thanks again for the very prompt responce.

I'll extra protect my PSU when leak testing my custom Hydro-X loop (which I'm about to do! - wish me luck!!)

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No leaks after 90 min - still purging minor air bubbles from the loop.

Fairly complex loop - GPU,CPU, 2 M2 SSD's, radiator, pump - I cut out 2 of the hexagons in the case top grid to allow me to add a 3 foot fill tube into the top of the pump.  Made filling system much faster & less messy.

This is probably my last build - I'm 80.

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heheheee don't underestimate one's nerdiness 😛 you have plenty of time to do lots of unneeded upgrades 😛

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1. I ran the leak test successfully.  Hydro_X pump purred along nice and quiet. 

2. I then hooked 2 GPU leads to PSU. The GPU is an Asus TUF Gaming RX 6800 with a EKWB water block (Corsair didn't make one). Removed the Corsair supplied shunt for the main motherboard cable, then attached that cable to the motherboard.  Checked all cables and wires. Then prayed!!

3. Turned power on at the PSU, the center fan on the radiator spun up very briefly, then stopped.  Otherwise-total silence.. Flipped the PSU swith to off - waitied 20 sec, then flipped the PSU switch back on - central radiator spun up again briefly (few secs) - otherwise nothing.  Tried thecase power switch - nothing!

1. Should the Commander Core attach to 1 or 2 USB2.0 headers  It has an additional female plug coming off the first 2.0 plug.  I've just let in "dangle" with its cover attached.

2.Does the fact that only 1 of my 5 fans briefly spins up tell you anything? (My pump is connected to position 6 in the Commander)

3. Do you have any ideas??? HELP!!!

TIA Doug

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the other conector is a male USB header, it's a passthrough, to connect something else like a second controller.

But make sure the SATA power to the controller is also connected, and that this dangling USB connector is insulated with its plastic cap or else you risk shorting 5V to ground if i touches an ything metallic.

Did you also plug the CPU power cable ? the 8 pin EPS12V cable

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  • Corsair Employees

Double check all of your connections, and make sure you are using the correct cables for all hardware, including the correct number of cables. Also make sure that you only used the cables provided with the power supply and that you are not reusing cables from a previous PSU.

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I slept well last night thinking you had found the real problem - not connecting the 8-pin 12V connector to either the PSU or motherboard - stupid me!

When I did the above connection this morning, I had high hopes! DASHED

Turned the power on - nothing! absolutely no sounds anywhere!  A month ago when I had the RM750x installed, the same exact thing happened after doing successful 24 hr. leak tests.  At that time, I put the system back into leak test mode to see if pump would still work - it did not, so for that and other reasons, I thought I had a defective PSU. Now, maybe not???

"But make sure the SATA power to the controller is also connected, and that this dangling USB connector is insulated with its plastic cap or else you risk shorting 5V to ground if i touches an ything metallic."  The male connector has always had its protective cap on.  SATA is connected to the supplied 3 connector PSU cable which is plugged into a PSU SATA slot.  The Commander's USB cable is connected to the motherboards labeled "USB_E12" USB2.0 header.


On motherboard (Asus Prime Z790 WIFI) in clockwise direction
1. 4 pin "ATX_12V_2" EMPTY
2. 8 pin"ATX_12V_1" connected to PSU (8 pin PCIe/CPU PSU output)
3. 4 pin "CPU_Fan" EMPTY
4. 4 pin "AIO_Pump" EMPTY
5. 4 pin "CPU_Opt" EMPTY
6. 4 pin " RGB header1" EMPTY (for Aura)
7. 4-1 pin  "ADD Gen2_1" EMPTY  (Note ADD=Addressable)
8. 24 pin "ATX_PWR"connected to PSU (18 pin Motherboard output & 10 pin Motherboard output) ???24 pins 1 end 28 on other ???)
9. 20-1 pin  "U32G1_78" USB 3.2 Gen 1 header EMPTY
10. ? pin "U32G2_C4" USB 3.2 Gen 2 Type-C front panel connector connected to front panel case cable.
11. 14-1 pin  "TPM"  EMPTY       
12. 4 pin " RGB header2" EMPTY (for Aura)   
13. 4-1 pin  "ADD Gen2_3" EMPTY
14. 4-1 pin  "ADD Gen2_2" connected to GPU EKWB water block
15-18. 4 SATA 6Gb/s ports EMPTY (system is all M2 SSD's)
19. multi-pin System panel header (I purchased a plug with  6" wires to RESET, PLED, PWRSW,Speaker - more accessible)
20. 20-1 pin  "U32G1_56" USB 3.2 Gen 1 header connected to case USB 3.0 front I/O connector   ???3.2 to 3.0???
21. 10-1 pin "USB_E34" USB 2.0 header  connected to Commander USP cable                                                                              
22. 10-1 pin "USB_E12" USB 2.0 header EMPTY
23. 2 pin "CLRTC" clear CMOS header EMPTY
24. 4-pin "CHA_Fan3" header EMPTY
25. 4-pin "CHA_Fan2" header EMPTY
26. 6-1 pin unknown header (next to Thunderbolt header) EMPTY  ???? not listed in motherboard manual or on web
27. 14-1 pin "TB_Header" EMPTY
28. 10-1 pin "COM" COM Port header EMPTY
29. 10-1 pin "AAFP" Front panel audio header connected to case audio cable
30. 4-1 pin "S/PDIF OUT" header EMPTY
31. toward center of MB  4-pin "CHA_Fan1" header EMPTY 

Your thoughts - wife thinks I was crazy attempting this!!

TIA  Doug

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I was just about to put the build away for a month while I got to taxes, however....

Setup: RM850x
    Motherboard: 18pin  & 10pin cables connected to Corsair shunt cap
    PCIe/CPU: 8 pin connected to motherboard "ATX_12V_1"
    PCIe/CPU: 8 pin connected to GPU (I've read numerous recommendations not to use 1 cable and pigtail???)
    PCIe/CPU: 8 pin connected to GPU
    SATA/PATA: 6-2 pin connected to XD3 RGB pump
    SATA/PATA: 6-1 pin connected to Commander

Test 1:  Tried a single Corsair RAM in the recommended slot (alternated both of my Vengeance RGB DDR5 16GB's) with all PSU connections
    Result: All 5 case fans spun up, pump started after about 3 sec.
    Note:  Loop has no air bubles, initially thought pump wasn't working so I removed the top cap on the pump - water started vibrating after about 3 secs. 

Further tests were done with no RAM

Tests 2: I removed all PSU connections except the 18/10 pin connected to the shunt and the 6-2 pin connected to the pump
    Result: Heard pump start up after about 3 sec, no running fans (fan on PSU runs slowly for about 10-15 sec)

Test 3&4: Added the 2 PCIe/CPU cables to the GPU
    Result:  AH HA! Difference

A guess - whenever I added a device (GPU or Motherboard 8 pin to any PCIe/CPU PSU  slot the pump sound went away but the water kept vibrating slightly - appears pump at max can be heard, adding device puts pump at lower speed???

Test 5: Added 6-1 pin SATA/PATA connected to Commander
    Result: All 5 case fans (includes the 3 radiator fans) spun up plus pump

General conclusion: Sadly, things are pointing to the motherboard!!! Getting to this will be a major project in a water cooled system!!

1.  I probably should have gone with a larger case!  I thought by eliminating all hard drives, CD, DVD's and regular SSD's a smaller case than my existing large Obsideon case should work!  As it turned out, the extra room would have helped (esp. with my 80 yr old clumsiness)
2. For anyone! I should have put together all my components without any water cooling devices added. Then powered up the system to check all basic hardware. Then loaded Windows.  After success, start adding water cooling components very, very carefully.  Be especially careful with CPU - maybe document steps with pictures!

ain't hind sight wonderful!!!

TIA - Doug

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1.  Additional Question:

My motherboard has empty 4 pin "ATX_12V_2" next to the connected 8 pin 12V socket.

The PSU has no corresponding connector
No applicable cable was supplied.

Please confirm that nothing should be connected to that socket?

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usually, only one 8 pin cable is more than enough as it can provide slightly over 300W.

you should have other CPU 8pin cables. the motherboard end of the cable splits into two 4 pin connectors. 

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This is a brief reply to the 4 pin motherboard connector labeled "ATX_12V_2" discusion

1. The RM850x PSU box did not contain any - "you should have other CPU 8pin cables. the motherboard end of the cable splits into two 4 pin connectors" - cables that split into 2 4 pin connectors.

2. I'm assuming that the 4 pin motherboard 12V connection should remain EMPTY. That is how I'll proceed (Nothing has ever been connected there during testing.)

I'm now preparing a wrap-up note which will contain a few important questions about the way forward.  I will not be able to pursue this for at least another month - have to get on taxes!  I'll post the note when it's completed on Notepad.

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First - Thank you to all, especially LeDoyen, for the suggestions, answers, and brainstorming in this thread.

Obviously, my attempted build is a $2500 plus failure.  I must decide on the path forward.  Right now, I'm leaning toward finding out which part or parts are failing.  I won't be able to pursue this for 4-6 weeks - got to do taxes (to keep out of jail!)

WORKING COMPONENTS (or likely working)
1. PSU: The RM850x appears to power the pump and all the fans
2. Hydro-X Pump: The XD3 RGB pump appears to circulate fluid.
3. Radiator: All 3 fans spin up 
5. Fans: All 5 case fans  (Incl. 3 rad) spin up.
6. Tubing: No leaks in all 6 tubing segments.
7. Fan controller: iCue Commander Core XT powers all fans and pump when connecter to the PSU.
  Note: No RGB function anywhere, but probably not expected

1. Motherboard: ASUS Prime Z790 WIFI
    a. CPU: Intel I7-12700KF - Need to disassemble motherboard to make sure pins didn't get bent!
    b. M.2 NVMe SSD's:  Need to test 1 at a time.  QUESTION: If the motherboard was good, would it "work" without any storage (SSD's)??
    c. GPU: ASUS Radeon RX 6800 The following questions might be better addressed to ASUS however if anyone here knows the answers, I'd  be very grateful! 
        1. I have a good spare ASUS Radeon R7 370 Strix Gaming GPU and could pull my ASUS Radeon RX570 to test out in the system -  Would they work with the new motherboard??  (I haven't researched this, but will if no one here knows the answer offhand)
        2. Would it be safe from a heat standpoint, to briefly power up the system with ne GPU cooling fan? Disassembling the EKWB water block would be a pain - nice if it could be avoided!
    d. Memory:  Corsair Vengeance RGB DDR5 (32GB, 16x2)  QUESTION: Can the motherboard be tested without any RAM??

Draining a fully water cooled system is a lot harder than filling it!!!  I need to figure out a way to suspend the case, front face down over a large tub/container so that I can unscrew all the Hardline fittings and remove all 6 tube segments. This would let the water drain without wetting any components.


Thanks again for your assistance!   



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  • Solution

seems your motherboard is a Z690-P Wifi 😛 I was confused the layout didn't match the Z790.

You can disconnect the pump from port 6 on the commander to see if it spins correctly (Disconnect it with the power off. hot plugging can fry stuff). That will force the pump to run at full speed since it won't receive any PWM signal.

With everything connected (except the pump PWM cable) If you can get the pump and fans to spin with the PSU shunt, then there's probably no short circuit anywhere. Otherwise, the PSU would click as you power it on and do nothing, with the short circuit protection immediately kicking in.

If the pump runs fine, then the PSU is providing 12V, showing that no short circuit protection is active.

When you plug back the 24 pin cable on the motherboard, there's still a possibility something could be conected wrong, but usually, it goes like this :

If you have a short on the motherboard or something connected to the motherboard (front panel busted, damaged USB device shorting 5V to ground for example), the PSU will just "click" when powering on, and do nothing. You'll have to flip the switch off and on to reset it.

If it's not a short, and the computer still does nothing, then it can be the CPU or motherboard.

When you press the start button, the CPU will normally latch the "power ON" signal to the PSU to make it start, wait for the "power good" signal to come from the PSU, telling it the PSU is started with all voltages in spec, then it will keep the "power ON" signal active and carry on with the system startup sequence.

If you have no short circuit, but still absolutely no response, then checking the CPU may be required, maybe as you said inspecting if no pins are bent on the LGA socket, or just re-seating the CPU. No fingerprints on the CPU contacts either 😛


With a watercooling build, it's always VERY adviseable to test the parts before doing the watercooling, to make sure they work before going to town and installing the blocks and tubing. The waterblock on the GPU is pretty massive so it's fine turning on the computer without water for a few seconds to check if you have a picture, like going to the BIOS screen.

Otherwise, any GPU can work, for testing. Even old PCIE 1.0 cards will work on a PCIE 4 or 5 motherboard. it's fully backwards compatible.

Since you have no response right from the power button, i would try to go bare bones. disconnect every cable from the motherboard and PSU and only connect the pump SATA power, CPU 8 pin power, motherboard 24 pin, one stick of RAM on slot A2 and the front panel power switch (just the switch, nothing else).

You can connect a fan to the CPU FAN header too, to look if the motherboard has power and makes it spin.


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Thanks again & again LeDoyen

1. Prime Z790-P WIFI - See attached picture of motherboard box label (I'm trusting that ASUS didn't mix up a box and a device!)

2. I've put everything away in a closet to get to taxes.  When I get back to the computer, I'll follow you guidelines.

3. Pretesting:  I read and watched many, many water cooled build instructions prior to starting.  Not one mentioned the (obvious now) need to test the setup first before adding any water cooling - sure wish JayZ 2 cents (think I got the name right) Corsair video had mentioned and emphasized this!  It sure is obvious in hindsight.

Hope you are still around in 4-6 weeks when I get back to this - will keep you apprised!

Thanks again

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