I removed the fan fuse. It does reduce a hot air blow inside the car but a hot air still comes in on the high speed with annoying whistling.
Is it possible to reverse a fan blow from inside to outside?
As I understand the mono valve controls the flow of the coolant to the heater core and it is electrical powered. And it is no mechanical valve, which I could close by hand to stop the coolant flow to the core.
Maybe I can short some contacts on the climate control unit connectors to close the mono valve?

Where is the mono valve located? How can access its wires to disconnect?

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1987 MB260E 187K