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Home >> Jeep >> 1979 >> Cherokee Base, 2D Utility, 4.2L Eng VIN C, AWD >> Repair and Diagnosis >> Engine Performance >> Ignition System >> Spark Control Systems >> Testing >> Coolant Temperature Override (CTO) >> Dual-Function
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Coolant Temperature Override (CTO): Dual-Function

Connect a vacuum gauge to port "2" (distributor) of CTO switch. When coolant is below 149°F, manifold vacuum should register. From 149-220°F, carburetor ported vacuum should be indicated. Above 220°F, manifold vacuum should again be indicated.