Cruise Control Switch and Speed Sensor Test

Please note that these ideas and procedures are for someone who has the time, inclination and technical ability to understand and follow them. There are other alternatives. We can generally tell you, over the phone or by email, what is wrong with your system if you let us know what the symptoms are. Or, naturally, you can have your favorite local qualified mechanic perform the work. Please do not hesitate to email or call us if you have questions or concerns.

These tests are performed with the ignition switch on and are measured at the Amplifier.

A) Switch Test (meter common to ground)

Pin 1 BV (BV = battery voltage: somewhere between 12.5 and 13.8 Vdc)
Pin 2 Decel/Set 0 Vdc initially - goes to BV for Decel/Set
Pin 3 On/Off BV initially - goes to 0 V for Off
Pin 4 Accel/Set 0 Vdc initially - goes to BV for Accel/Set
Pin 6 Resume 0 Vdc initially - goes to BV for Resume
Pin 8 Brake Disengage MUST BE 0 Vdc for Cruise System to work - goes to BV when you step on the brake.

The system gets a critical ground through the brake light bulb filaments. If both bulbs are burned out or there is not proper ground here the system will not work. This is the mechanism for canceling the Cruise when you step on the brake: this pin goes from ground to plus voltage and loses a ground which is necessary for the stem to stay engaged.

Pin 12 Ground
Pin 14 Ground (some cars have no ground here; the system will work without it)

B) Speed Sensor Test (meter common to ground)

This test must be performed with the rear wheels turning. Please have two qualified people present at all times.


Pin 11 Speed Sensor loaded (with the amplifier plugged in) must be at least 2.0 Vrms at 25 mph.


The amplifier actually measures the frequency of this signal. At 60 mph the frequency should be 131 Hz.


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General Development Laboratories
3041 Sandalwood Avenue
Morro Bay, CA 93442

805 772-5127