I decided to change my case fan on a whim for a quieter one. Replaced OK. When I started it up and ran the Asus Probe monitoring, it showed the PSU fan speed intermittently going to zero. The fan itself ran normally at constant speed. I put the old case fan back in and it ran normally.
The revelation was that the case fan is plugged into the MB PSU fan socket. The PSU monitoring connector was hidden in the wiring bundle, unconnected. The remedy seems obvious but I wonder if the local guys that built the PC knew something I don't. The MB is an Asus A7V8X, Athlon 2200+. The PS is an Enermax EG365P-VE. The questions I have are:
1. Even if the case fan was plugged into the PSU fan socket, why would the indicated speed be erratic (other than defective fan)? I presently have the CPU fan on speed control. The MB manual is not very clear whether that PWM is applied to all fans. All MB fan connection sockets are 3-wire.
2. The monitoring connection for the PSU fan is 2-wire, Common and Rotation. I was expecting 3-wire even though the fan is constant speed only. Does the +12V for the tacho circuit come from the PSU rather than the MB? If it does, why bother with the common and only use the tacho wire?
Edit: Part 2 FYI
While I was looking at the fans I realized that there is a location above the case fan for a 2nd fan. It was open to the outside. Great for the PSU inlet fan drawing in outside air but it short circuits the case fan. I taped over the grill (not completely as shown in the pic, bottom uncovered). The MB temperature went down 4 degC, the CPU temp down 2 degC and the HDDs down 2 degC. I have no indication of PSU temperature.
The revelation was that the case fan is plugged into the MB PSU fan socket. The PSU monitoring connector was hidden in the wiring bundle, unconnected. The remedy seems obvious but I wonder if the local guys that built the PC knew something I don't. The MB is an Asus A7V8X, Athlon 2200+. The PS is an Enermax EG365P-VE. The questions I have are:
1. Even if the case fan was plugged into the PSU fan socket, why would the indicated speed be erratic (other than defective fan)? I presently have the CPU fan on speed control. The MB manual is not very clear whether that PWM is applied to all fans. All MB fan connection sockets are 3-wire.
2. The monitoring connection for the PSU fan is 2-wire, Common and Rotation. I was expecting 3-wire even though the fan is constant speed only. Does the +12V for the tacho circuit come from the PSU rather than the MB? If it does, why bother with the common and only use the tacho wire?
Edit: Part 2 FYI
While I was looking at the fans I realized that there is a location above the case fan for a 2nd fan. It was open to the outside. Great for the PSU inlet fan drawing in outside air but it short circuits the case fan. I taped over the grill (not completely as shown in the pic, bottom uncovered). The MB temperature went down 4 degC, the CPU temp down 2 degC and the HDDs down 2 degC. I have no indication of PSU temperature.
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