I believe it is #38 the spring nut you are looking for on this drawing. Even expanding the drawing it is hard to see on the left hand of the radiator as seen in the picture. https://www.volvocarstorontoparts.ca/a/Volvo_1996_850-25l-5-cylinder-Fuel-Injected/_51956_7337910/Air-conditioning/GR-439909.h...

I replace those with M6 hardware in cheap stainless which makes removal a lot less painful.

Zip tie two opposite corners to hold the sand which together, install bolts into other corners, then cut ties and do the first corners.

If you jump the ground and power wire on the fan and you get nothing, then sorry, but sounds like the fan motor has failed. Not a common failure but at this age it can happen.

Neil.

I'm going to guess it's the fan itself.

Odd that it turned on when you unplugged the ECT, but seeing as you're replaced the relay (and verified that the connector/connections were good and clean), I would mostly rule that out as the culprit.

The Oem fan 9497929 is no longer made at Volvo but the good news is it’s a p80 model part spanning 1992-2000 models.

As Professor Potato teaches us, two words , “junk yard “

Four seasons makes an aftermarket for $130 if you hurry and beat the consumer import tax, it’s part number 843-05100704

Have you checked the fan relay and wiring on the top of the radiator? The wiring connectors and the relay can go flaky.

Neil.