I think that PSU is too old to have that feature. It's not a good idea to take a PSU to bits unless you know what you are doing. A PSU is basically a AC/DC convertor & step down transformer in one so there's some fairly dangerous voltages & current inside. They have capacitors which store a certain amount of current when switched off, leave it off for a while before plunging in.
I think other people on here have tried & replaced PSU Fans successfully or have killed the PSU in the process.
Either way a failed fan on a PSU that old would give me an excuse to buy a new PSU.