Fans only spin for half a second?

floppysnappy · Dec 23, 2013

Ok, so my Cpu's heatsink and Gpu's fan only spin for half a second, the motherboard i have is a gigabyte ga-78lmt-usb3 a AMD Radeon HD 7750 1TB HDD and a AMD 4 core cpu (can't remember the name of the cpu or the speed) I breadboarded, made sure every single wire is on correctly and the 4 pin 12v connector and 24 pin. I'm positive its not my PSU (which is 300 watt) because i have an old computer which still runs and put my power supply in that one and it turned on like nothing changed, but when i hook it up to my new motherboard the fan only spins for half a second and won't turn on unless i turn off the PSU for about 5-10 seconds, i even used my old computers PSU and it did the same thing, fan only half a second, turn off 5-10 seconds, jump the switch with a screwdriver to turn it on. I tried it all! Do i just need to get a new motherboard?!

ronintexas · Dec 23, 2013

Make sure that all items are installed correctly on the mobo (RAM, GPU, power connections). RAM not installed properly could create the issue.

ihog · Dec 23, 2013

It is recommended to have at least a 400W PSU for a system with a 7750 in it.

http://www.amd.com/us/products/desktop/graphics/7000/7750/Pages/radeon-7750.aspx#3

floppysnappy · Dec 23, 2013

Thanks for the fast replys! Without the GPU inside and just the CPU, Heatsink and fan. The fan still only turns on for half a second.

ronintexas · Dec 23, 2013

You need RAM to get to BIOS screen and/or boot.

floppysnappy · Dec 23, 2013

So for the fans to spin i need ram installed?

ronintexas · Dec 23, 2013

Yes. The mobo will detect no RAM installed and shut down.

floppysnappy · Dec 23, 2013

Man did u save me hundreds of dollars and time! I've spent 2 days looking up my problem, and nothing popped up about the way you explained it, without ram. Thank you so much! I have DDR3 2x4 GB 1066 G.skill on its way now through the mail.

ronintexas · Dec 23, 2013

Most modern mobos will have protection that shuts down everything if a short is detected anywhere in the system, critical components (CPU, RAM, GPU) are missing or installed wrong or there are heat issues (possible fan not spinning, bad thermal paste, etc). Better to shut down immediately than to create a bigger issue.

floppysnappy · Dec 23, 2013

Makes a lot of sense, I thought i was going crazy when it barley even turned on! Thought i broke it and was scared i had to buy a new one. Now i know i had everything wired correctly.

ronintexas · Dec 23, 2013

I have built and repaired computers for almost 30 years - still have the adrenalin rush when powering up a PC for the first time....LOL. Good luck with your build!

floppysnappy · Dec 23, 2013

Lol! I can't wait to see this thing power up! So excited, and Thanks!

kaywhyinkc · Feb 26, 2014

Was having this same problem. Fan comes on for a second and then everything quits. I was sure I built everything correctly but sure enough the memory module of all things came loose probably while installing the video card. After pushing the memory back down she boots all the way. Yay!

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