Cruise Control Servo: Testing and Inspection

Perform the speed control servo resistance checks:

1. Key OFF.
2. Disconnect the speed control servo C175.
3. Disconnect the C228 from the speed control amplifier.
4. Measure the resistances between the following wires at the speed control amplifier:

Wire Colors Resistance

GN/W - GN 20K-30K ohms
GN/O-GN/W 40K-60k ohms
GN/O - GN 20K-30K ohms
BL - GN/BK 40-70 ohms
BL-BL/R 150-210 ohms
GN/BK - BL/R 110-140 ohms


Perform the speed control servo operational checks:

5. Key OFF.
6. Disconnect the speed control amplifier C228.
7. Apply 12 volts at the, speed control amplifier C228-5, "GN/BK".
8. Apply ground at the speed control amplifier C228-7, "BL/R."
9. Key ON, engine running.
10. Momentarily touch the "BL" wire with a jumper to ground.

CAUTION: Do NOT ground the "BL" wire for more than 1 second to prevent over-revving of the engine or damage to the speed control servo.

11. Remove the jumper.
12. The actuator arm should pull in when ground is applied to the "BL" wire and release when the "BL" wire is removed.
13. If the speed control servo does not operate as specified, replace the speed control servo. Otherwise, return to the Pinpoint Tests. Pinpoint Tests