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Volvo heater core

I have a 91 Volvo 740 that used to have great heat. The heater core died and was replaced at a Volvo shop (not dealer) and the heat now is not good. I took it back and they replaced the thermostat and agreed that the heat wasn’t good. Even the hoses going to the heater were only warm, not hot. Any ideas?

Did the new thermostat solve the problem?

No, it made no change.

I wonder if they might have damaged the heater controls when they replaced the heater core?

I don’t know, it feels like the knob that makes it hotter in the car is only on 5 or 6 out of 10 even when it is on 10. Before the core went bad and was replaced it was HOT air coming out when the knob was all the way on.
Is it possible to damage the heater controls when you replace the heater core?

If the hoses to the heater core are not hot something is restricting the flow of coolant. I’m assuming the engine itself reaches normal operating temperature with the new thermostat. Does it?

My guess is something is impeding the flow of coolant to and through the heater core. If there was flow the hoses should get hot. I would assume a new or rebuilt heater core was tested to assure good flow. Sometimes assumptions get us into trouble.

If not the heater core itelf; perhaps a wire or cable from the heater controls is disconnected? You are moving the knob on the dash, but is it doing anything at the other end? Another possible is a hose got pinched in the installation process and is allowing only a minimal flow.

I believe the engine reaches temp. Everything temp. wise was fine before old heater core died.