There's a few moments in the Night Lords series, notably in Void Stalker when one of the Night Lords' back generator gets shattered by a Thunder Hammer. His life signs cut off before even registering a flatline, so everyone assumes he's dead. Afterwards, it's revealed that he didn't die, just couldn't actually get up so he lay there and hoped the loyalist would think he was dead. I think one of the others gets their armour damaged in the same way, and it's described as suddenly being able to feel the immense weight of the ceramite plates. The comparison to power assisted steering is in my opinion quite accurate; imagine going from driving your car to having to Flintstone it with no power steering. You can still move it, but it doesn't exactly function. In the same series, a Terminator describes his suit as becoming slow and sluggish with all the damage it's sustaining as he wades into bolter fire; a similar depiction, in my opinion.