Please help troubleshoot PSU.

[Lerpy]

The last couple months my secondhand Corsair TX850M has been intermittently running the fan at full speed, but the casing is still cool to the touch and the air coming out the back is barely warm. It also revs up when the computer is idle, and I can't find a link between component temps and PSU fan activity.

It's has been used in two cases, both with plenty of ventilation to the PSU. Other specs are as follows:

4790K @ 4.6 1.27v
2x SSD, 1x HDD
R9 280X (dual-x)
Maximus VII hero (also used with Z97 Gryphon)
Phanteks Enthoo Pro M (also used with Corsair Air 240).

So far I've tried the following:
Remove PSU fan covering, add silicon lube, replace.
Noticed GPU becoming very hot even when not in use, but fans not running. Removed GPU. Didn't fix the PSU problem, but it stopped a couple random crashes (with no blue screen) I got when doing CPU intensive tasks.
Noticed HDD warm to the touch. Removed HDD. Didn't help.

I also noticed the back of my motherboard was quite warm when I held my hand to it while working in the back of the case. I don't have another mATX mobo to test.

At startup the PSU fan twitches a little but doesn't fully spin. It's also sometimes made little grinding noises similar to a HDD, although not since I lubed it.

At this stage I'm thinking I just have an old dying PSU that needs to be replaced. Is there any way that it could be causing my other components (GPU, HDD, mobo) to be running hot even when not under load?

Would love to hear some other thoughts or suggestions to try before I bite the bullet and buy a EVGA 550w G2. Thanks!

 

[Doramius]

got a pic of the inside of the case? Especially where the wires are going to? Some PSUs have a sensor that goes to the mainboard so the mainboard can control the fanspeed of the PSU as if it were a system fan. If yours has one, what fan header on the mainboard is it plugged into?

 

[Lerpy]

I can't take photos, but the PSU does not have a specific cable for a fan header. Just the usual 20pin mobo cable and the CPU cable.

 

[Doramius]

I'll let you use your own discretion, but I will provide the standard warning that opening the PSU can be dangerous because of voltage charges stored in capacitors, even when unplugged. You do this at your own risk. You can open the PSU and see if there is a thermistor sensor on it. However, if it does and it's not functioning, there's probably very little you can do about it. If it does have a thermistor, you should be able to remove it without it disabling the PSU.

You could also get a 1KΩ variable resistor and connect it to the hot line of the fan. Then you'd have a variable speed fan.