Servo Assembly Test

Separate 8-pin connector at amplifier. Check for proper resistance values on harness connector. See SERVO RESISTANCE table.

SERVO RESISTANCE

Circuit		Ohms
Aerostar, Bronco II & Ranger
144 (Orange/Yellow) - 145 (Gray/Black)		40-70
144 (Orange/Yellow) - 146 (White/Pink)		100-150
147 (Purple/Blue) - 149 (Brown/Green)		35,000-70,000
147 (Purple/Blue) - 148 (Yellow/Red)		15,000-35,000
148 (Yellow/Red) - 149 (Brown/Green)		15,000-35,000
Bronco, "E" & "F" Series
144 (Orange/Yellow) - 145 (Gray/Black)		40-125
144 (Orange/Yellow) - 146 (White/Pink)		60-190

NOTE: Resistance between circuits No. 147 and 148 should be nearly the same as resistance between circuits No. 148 and 149. If the difference is more than 5 k/ohms and vehicle has a surging problem, follow step 2).

If resistances are not correct, disconnect 6-pin connector at servo. Ensure terminals are clean. Recheck resistances at this connector. If resistance is correct, check wiring harness for continuity and repair as necessary. If resistance is incorrect, replace servo and retest.
If resistance is correct, disconnect servo and start engine. Ensure vacuum to servo is at least 2.5 in. Hg. Connect circuit No. 144 (Orange/Yellow wire) of servo to positive battery terminal. Connect circuit No. 146 (White/Pink wire) of servo to ground. Momentarily touch circuit No. 145 (Gray/Black wire) of servo to ground.
Servo throttle actuator arm should pull in and engine speed increase. The throttle should hold in that position or slowly release. When circuit No. 146 (White/Pink wire) is removed from ground, servo should release. Replace servo if it fails test.

CAUTION: If Orange/Yellow wire is shorted to either White/Pink wire or Gray/Black wire, it may cause damage to amplifier.