Here is a brief description of the system operation, although sounds like you have that figured out. The Amp is under the dash on the drivers side, above the kick panel a ways. It is a black looking box and wires run a short distance out to the servo.
Description and Operation
The speed control system is composed of On-Off, Set-Acc, Coast and Resume switches. The system contains vacuum hoses, servo (throttle actuator) assembly, speed sensor, amplifier, check valve assembly, and depending on model and year, a clutch switch, a manual lever position switch, stop light switch, or vacuum dump valve, an actuator (servo) and an actuator cable.
To operate speed control system, engine must be running and vehicle speed must exceed 30 mph. When On-Off switch is actuated, the system is ready to accept a set speed signal. When vehicle speed stabilizes (above 30 mph), and the On switch is engaged, the operator may depress or release the Set-Acc button. This speed will be maintained until a new speed has been set, brake pedal has been depressed, or the system is turned off.
The vehicle speed may be reduced by applying the brake or clutch pedal and then resetting the speed using the method outlined above or by depressing the COAST switch. When the vehicle has slowed to the desired speed, the COAST switch is released and the new speed is set automatically. If the vehicle speed is reduced below 30 mph (48 km/h), the operator must manually increase the speed and reset the system.
Switch Testing
Testing and Inspection
Disconnect connector at the amplifier assembly, refer to SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC DIAGRAMS. Perform the following checks:
1. Connect a voltmeter, part No. 014-00407 or equivalent between the light blue-black lead and ground. Depress the On button and check for battery voltage.
2. Turn ignition Off and connect an ohmmeter between the light blue-black hash lead and ground.
3. Rotate steering wheel throughout its full range while making the following checks:
1. Depress Off button and check for a reading between 0 and 1 ohm.
2. Depress Set button and check for a reading between 714 and 646 ohms.
3. Depress Coast button and check for a reading between 126 and 114 ohms.
4. On models which incorporate Resume, depress Resume button, check for a reading between 2310 and 2090 ohms.
4. If resistance values are within specification but needle fluctuates, remove steering wheel and clean the brushes. Apply a light coat of lubricant ESA-M1C189A or equivalent to the slip rings. If resistance values are above the allowable limits, check the switches and ground circuit.
5. Reconnect the connector at the amplifier.
Cable Adjustment;
1. Remove the cable adjusting clip from the cable housing.
2. Pull lightly on the cable until all of the slack is taken out.
3. Maintain light pressure on cable, then install the cable adjusting clip and snap into place.
Servo testing: Also make sure that you have good vacuum at the servo.
Testing and Inspection
1. Separate the eight pin connector from the amplifier.
2. Connect an ohmmeter between the orange/yellow (circuit 144) and the grey/black (circuit 145) leads at the eight pin connector, refer to SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC DIAGRAMS. Resistance should measure 40-75 ohms.
3. Connect an ohmmeter between the orange/yellow (circuit 144) and the white/pink (circuit 146) leads at the connector. Resistance should measure 100-150 ohms.
4. Connect an ohmmeter between the purple/light blue (circuit 147) and Yellow/Red (circuit 148) leads. Resistance should measure 20,000--30,000 ohms.
5. Connect an ohmmeter between the purple/light blue (circuit 147) and brown/light green (circuit 149) leads. Resistance should measure 40,000--60,000 ohms.
6. If proper resistance is not obtained check the wiring and servo separately for damage and replace or service as required.
If you don't have an Alldatadiy account it is very helpful, that is where I found most of this info.
