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Hello and welcome to just answer,
Do you have auto or manual a/c?
Auto has "degree" temperature settings and typically an "auto" button.
manual has temp setting of C to H or blue to red ands no auto button.
Reviewing the schematic and from your symptoms and descriptions the blower relay (6) is sticking closed. I have included the shcematic and relay location below.
With the blower relay stuck closed... the resistor board "which controls blower speed" is taken out of the circuit and blower is stuck on high.
Everything else works because this does not affect other circuits other than blower.
I would tell you to swap with another relay for testing but disconnecting and reconnecting will typically jar relay to "unstick".
The blower relay is about one of the least inexpensive A/C repairs "you lucked out on this one".