I built my system about a year ago and it has been working fantastically but I recently wanted to overclock my i7 960, so I replaced my stock cooler with the Antec Kuhler 620. Since then my system has issues booting where it will turn on for 3 seconds, not post, and then shut down. It does this 3 times in a row and then turns on like normal. I thought it was a thermal shut down because I messed up the thermal paste on the initial installation, but I bought a tube and reapplied (what I thought) was successfully but still the same issues.
Sometimes if a fan is not pluged into the cpu fan socket next to the cpu soket you will get an error message or maybe in this case a shutdown. You can get around this by codeing it as disabled in the bios. That's asuming you didn't plug the fan on the radiator into the cpu fan socket.
On a side note when you applied the thermal compound did you spread it in a very thin layer and I do mean very thin , because if not if you put too much it would actually act like an insulator and not let the heat be transfered.
Have you rechecked your connections in case when you were working in the case you didn't accidentaly loosen a cable?
The cooler itself has 2 fan connections, 1 for a fan and 1 for the radiator itself. The radiator is plugged into the CPU Fan header on the motherboard.
When I applied the thermal compound I did a pea size dab in the center of the CPU, (I don't have much experience with thermal compound). I haven't checked my connections yet.. I'll post a result when I do.
The radiator has a pump in it and that's what you pluged into the cpu fan socket , I would take that out and connect the fan there. The cpu fan header is controlled by the bios and is supposed to control a fan and not a pump so that could be your issue.
Tried several different locations for the radiator, and with or without fan. Any time the CPU fan connector was empty my computer would not boot, as to be expected. Same boot issue throughout all configurations it will act like its turning on but no splash screen, no post. I just get fans and MOBO lights. And when it does want to turn on it begins to act like I previously mentioned but it will suddenly shut off and automatically turn back on. It finally posts on the 3rd round and my computer functions as normal... When it makes it past turning it on. Could it be something with my BIOS, or CPU?