Next to the Comp. there is a three prong plug clipped to the Vac hose.
Black wire "A" to the back of the Comp.
Green wire "B" to a relay on the fire wall.
Green wire "C" to the front of the comp.
What plugs into this three prong plug?
It gets a, new for 72,"Thermal fuse". The black wire is connected to the superheat switch on the back of the compressor. On a low system charge condition the superheat switch closes to ground, completing the circuit of a heating element inside the thermal fuse that melts a fuse link. When this happens the power to the compressor clutch is blocked. You don't need the fuse you can bypass it by jumpering green to green. The general installed it to reduce the cost of warranty repairs on the A/C system.
If used it needs to be bypassed before recharging after servicing that requires a complete discharge if the system.
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