H60 cooler cycles on and off every 3-4 seconds

[hfffoman]

I just installed a new motherboard and the CPU fan isn't working. Consequently it won't boot. A bit of detective work is needed here. If I explain the exact situation there are enough clues for someone smart to figure it out.

 

The old board was professionally installed and instead of plugging the CPU fan connector onto the motherboard they plugged the two power wires directly into a power cable from the PSU. That leaves a single wire in the connector which goes into the IN pin when the connector is correctly located on the motherboard. This arrangement always worked fine and I think it's recommended by Corsair. The new motherboard is similar to the old but slightly upgraded (ASUS Z97-P instead of ASUS P8Z68V-LX). It has exactly the same fan socket configuration.

 

When I first turned on the motherboard the fan didn't work at all. The machine started to boot. Of course the CPU temperature started to rise and I quickly turned it off before it went above 34C.

 

I found that one of the CPU fan power leads was loose. I then made sure it had a good contact and next time the fan worked. But it cycled on and off every 3-4 seconds and the computer wouldn't boot. When I pressed the manual override on the fan it still turned off after a few seconds.

 

I then unplugged the connector with the single wire from the motherboard. The behaviour of the machine was exactly as before - the fans runs on and off every few seconds and it won't boot. This suggests the signal isn't getting through from the motherboard to the cooler.

 

I then got hold of a cheap fan with a conventional connector and plugged this into the motherboard. The fan works as normal and the machine starts to boot. Again I quickly switched it off because the working fan wasn't attached to the CPU.

 

So it looks like one of several possibilities:

 

1. The new motherboard won't tolerate the unconventional connectors. I would be surprised if this were the case given the similarity of the boards.

 

2. The wire is broken. I can't see any sign of damage but it probably got pulled a bit in the course of changing the motherboard.

 

3. The cooler is bust. However, the last time the cooler was switched on, with the old board, it worked fine.

 

Thanks for any advice.