Heater Core Bypass

heater core
A finned unit located in the passenger compartment and through which coolant from the engine flows to heat the unit. A fan blows air over the unit to heat the passenger compartment
A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core, a heat exchanger between coolant and cabin air.
The heater core is a miniature radiator that sits in the dashboard area. When the heater is turned on, it opens the heater valve which lets hot coolant into the heater core, which then warms the air coming into the vehicle's interior.

bypass
Avoid or circumvent (an obstacle or problem)
avoid something unpleasant or laborious; "You cannot bypass these rules!"
a surgically created shunt (usually around a damaged part)
Go past or around
beltway: a highway that encircles an urban area so that traffic does not have to pass through the center
Provide (a town) with a route diverting traffic from its center