I have a Dell dimension 4600 desktop on the bench with a JMC-Datech 9232-12hb cooling fan which is attached to the case and draws air through the heatsink by way of a cowling over the heatsink. It has a thermistor set up on the stationary hub of the fan housing which monitors the air temp, and adjusts the fan speed accordingly.
The problem is the fan is running fne until the computer is stressed. While using a burnin test, the fan begins to ramp up in speed and then when it reaches high rpm's it shuts down then ramps up over and over again. Sounds just like a heavy breather over the phone.
I have already changed out the fan and now have a working cooling system.
My question is--> has anybody out there ever seen this type of behaviour in a thermistor controlled fan , and could it be indicative of any other hardware failure on the motherboard itself?