XC60 Heater Core

[miznitic]

I'll be creating two separate posts for two distinct unrelated issues.

This issue here is regarding the heater core. I had to replace the radiator prior to start of last winter. When testing the replacement radiator, I used mostly water. We had a freak early snow storm and I drained the system of the water and all survived well, I thought. Several days later once temperatures returned to normal, I started the car after filling it with coolant. After getting almost to temperature, there was an obvious leak behind the dashboard. Flash forward to a few days ago.

I took the center section out and got to the heater core. Apparently not all water was removed and it froze, damaging the heater core connection. MacGyvering the thing, I put two rubber heater hose fittings around the heater core connection and the tubes with appropriate clamps (a nightmare and a half all together). I filled it with coolant again, and its holding pressure perfectly fine.

The problem is now when idling and small test drives, the heater core does NOT get hot. I haven't put it entirely back together as its a nightmare to take apart (e.g., that one drive's side screw behind the radio). Is there a valve or something that stops coolant from going to the heater core when the heater isn't activated? I reviewed the VIDA diagram for the heater system, and it doesn't quite make sense to me.

[miznitic]

Note: it's a 2010 T6 with the ECU Flash upgrade. Has about 200k miles on it and it is mostly used as a comfortable winter beater.