Pavilion 790 power supply fan doesn't spin

[Bobiverse]

I have a new Pavilion 790-0019 Desktop Gaming Computer. It seems to work fine, but I notice that the power supply fan does not spin, except for about 2 seconds at startup. Other than that, it never turns. I applied a heavy load to the machine (about 240 watts) for over 30 minutes, and still nothing. (Maxed out the CPU, GPU, and memory.) The top case fan operates normally.

It is a 400w PSU, HP part # 942332-001, model # 400W ENT18 EPA92, made by LITE-ON TECHNOLOGY model PA-3401-1. There is a small 7-pin connector from the PSU to the motherboard that appears to be secure.

Is this normal behavior? Even if it doesn't spin under low loads, I did expect that a high load would activate it. Since it spins briefly at startup, I presume the fan is operational.

Does anyone have a Pavilion 790 that can see if their PSU fan spins?

[Bobiverse]

I called HP support, and was given different phone numbers to call... 5 different times. Eventually, I was given the same number as an earlier call. Sigh...

They didn't know the answer. Closest they could answer was that it might just spin up when needed, but they had no idea under what conditions that might be.

I'm concerned that long-term use of the system with a non-functioning PSU fan might eventually cause it to die an early death. After some gaming, if I open up the case and feel the outside of the PSU, it feels fairly warm (about 45C). I imagine the inside components are getting much warmer than that.

If others with a similar system are seeing the same thing as me, then it's likely not a problem.

Anyone?

[Park_KS]

I just got a custom build Pavilion Desktop 790-0050t with the same issue.  Returned it and the replacement machine works the same way.

https://h30434.www3.hp.com/t5/Desktop-Hardware-and-Upgrade-Questions/Power-Supply-Fan-Not-Spinning/m...

[Bobiverse]

Yeah, after more testing, I'm pretty sure it's normal behavior for the power supply fan to (almost) never spin. I believe it's temperature-based.

I stuck a hair-dryer in the PSU fan vent opening, and ran it on high for a couple of minutes. I monitored the PSU and SDD temperatures, to make sure it wasn't getting the system too hot, and it only raised the internals by about 10 degrees. However, the PSU fan eventually starting spinning slowly, and stayed that way for a minute after I removed the hair dryer.

My guess is that the fan voltage is controlled by a thermocouple, or something like that. The hotter the PSU gets, the faster it will spin? Obviously, it has to get fairly hot for it to work, which never seems to happen during normal use.

I guess that's good. The case fan seems to do all the work under normal operating conditions.

I am disappointed in HP support, since they clearly have no idea how their systems are supposed to operate.