Well blimey, I've had the full spectrum now: Started with no heat, fixed that, then had a nightmare attaching the cable, then had it stuck on full heat again, and now I've fixed that but had to detach the cable again (which I'll re-attach properly as per BugJam's post).
So, the brand new heater control valve was stuck on full, even with the cable disconnected, and the control valve actuator 'clicked' onto full cold by hand. Turns out the thermostatic adjustment screw was off (the one poking out from the middle of the front of the mechanism towards you). I had a look at
this page (Full URL:
https://240seriesparts.com/tag/volvo...control-valve/), although it didn't mention which way to adjust the thermostat screw for a desired outcome (i.e. one way for hotter, the other for colder).
From experimentation just now:
- CLOCKWISE = COLDER
- ANTI-CLOCKWISE = HOTTER
Hopefully, this completes an otherwise excellent write-up by the linked article (and yes, I have archived that page so it should always be viewable on the Wayback Machine).