My laptop's CPU fan is suddenly acting very bizarre, and I am at a loss for what to do so I am asking for some help.

Specifically, the fan is not even starting to spin until the CPU reaches 60 degrees Celsius (checked through HWmonitor). Once it is on, however, it properly stays on even when the CPU gets back to idle temps around 38 Celsius. Before, the fan was simply starting with the computer and staying on like normal.

I've checked this for consistency both by allowing cold boots to ramp up temperature to 60 Celsius (the slow climb also causing the laptop to become unreasonably warm near the heatsink), and also running Prime95 immediately to kickstart the fan (this works every time).

The fan seems to be stationary when turning the computer on from either sleep or shutdown. The fan will start at POST very briefly, and then stop completely. I've checked the BIOS for a SmartFan setting but haven't found any.

I've opened the case to check for dust or debris and have not found anything (I applied some canned air to the area just in case). The laptop is a Lenovo ThinkPad Edge E430 and the CPU is an Intel Core i5 3210m @ 2.5 GHz.

Any advice would really be appreciated.