Reving the engine won't change the steering force as it is SPEED sensitive and not REV sensitive
It gets a signal Al via the ABS sensors or better said a speed output and then will alter the pressure.
My parents 500 has an issue like that... The steering is all well and good at very slow speeds but the moment it exceeds the city steering limit, it turns super heavy, absolutely no assistance. So I would expect here that the assistance isn't there.
Question is:
- pure hydraulic power steering
OR
- electro hydraulic?
Electronic hydraulic would need a signal to turn it on, which you would be able to hear when you turn the steering wheel. Pure hydraulic would be on the belts and will be on all the time. Volvo switched somewhere around 2011/2012 to full electro hydraulic.