Are you wanting to bypass the heater core to improve ac performance? If so,
first try just clamping the heater core inlet hose off with a C-clamp. Use
a small piece of wood on each side of the clamp. I found bypassing the core
didn't make a noticable difference on a S10. Also on some setups, the
heater flow circuit is the bypass for when the thermostat is closed.
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