Just making a SWAG to get discussion going. I've been kicking the can on hall sensor #3 and rear/left rope repairs because C70 roof stuff intimidates the heck out of me. So I need to change my mindset about that and get smarter about our fancy roofs.

Take a look at instruction for replacing position sensor at https://www.volvoclub.org.uk/tech/c70/ConvertibleRoof.pdf. Looks like it's p/n 31256538. I believe supply comes from the CRM, check connection/continuity. I don't have the wiring diagram, don't know pin #. Curious to hear from @volvogod or @Facusan if all of that is off base.

 

Well, I haven't touched my roof at all (and have no plans at all in doing so. Hope I didn't jinx myself), but replacing the sensor shouldn't be a big deal. Just don't rush it, open the roof, find a way to secure it so it doesn't fall on you, write a checklist of the locking devices you installed and removed, so you don't miss anything before moving it and that should be all. I haven't seen how the hall effect sensors are wired, but if they don't have plugs, don't use butt connectors, solder them and use heat shink. Butt connectors are unreliable.

 

Short to ground, short to supply... can also be pinched wires somewhere