My cruise control does not always work and then when it does set it frequently disengages.

Do you know how it works ? What controls it ?

Did you hook up a scan tool an check for DTC'S - diagnostic trouble codes ?

Cruise Control Description and Operation
Cruise control is a speed control system that maintains a desired vehicle speed under normal driving conditions. However, steep grades may cause variations in the selected speeds. The electronic cruise control system has the capability to CRUISE, COAST, RESUME SPEED, ACCELERATE, TAP-UP or TAP-DOWN.
The main parts of the cruise control system are:
• The powertrain control module (PCM)
• The function control switches
• The stop lamp switch assembly
The cruise control system uses the powertrain control module (PCM) to maintain the desired vehicle cruise speed . The PCM assembly contains a low speed limit which will prevent system engagement below a minimum speed of 40 km/h (25 mph). The PCM assembly is not serviceable.
Cruise control operation is controlled through the function control switches located on the multifunction turn signal lever. The cruise control function control switches includes the ON/OFF, SET/COAST, R/A (resume/accelerate). The switch assembly provides driver control of the cruise control system.
The stop lamp switch is used to disengage the cruise control. A cruise control release switch circuit and a stop lamp switch circuit are used. The stop lamp switch is mounted to the brake pedal bracket . To disengage the system the driver presses the brake pedal. The speed of the vehicle at brake actuation will be stored in the memory of the PCM.
With cruise control, the vehicle can maintain a speed of about 40 km/h (25 mph) or more without keeping your foot on the accelerator. When the driver turns off the cruise control ON/OFF switch or ignition switch, the cruise control turns off. The vehicle speed stored in the memory of the PCM will be lost.
Ignition positive voltage is supplied from the HVAC fuse, to the cruise control switch. When the cruise control ON/OFF switch is on, ignition positive voltage is applied to the cruise on switch signal circuit terminal of the PCM. If the driver has not pressed the brake pedal, ignition positive voltage is supplied through the stop lamp switch, TCC/Brake signal contacts to the cruise control brake pedal switch signal circuit terminals of the PCM. Cruise control is canceled when the driver presses the brake pedal. The stop lamp switch contacts close, applying battery positive voltage to the stop lamp signal circuit of the PCM. At the same time, the TCC/Brake contacts of the stop lamp switch open and voltage is removed from the brake pedal signal circuit at the PCM. When pressing the SET/COAST button on the multifunction turn signal lever, ignition positive voltage is applied to the set/coast switch signal terminal of the PCM. When pressing the R/A (resume/accelerate) on the control switch, ignition positive voltage is applied to the resume/accelerate switch signal terminal of the PCM.
When the cruise switch is in the ON position, and the driver presses the SET/COAST button, the PCM then checks to see that the cruise control enable criteria is met. If the cruise control criteria has been met the PCM sends a class 2 message to the instrument panel cluster (IPC) to illuminate the cruise light.
The PCM will inhibit cruise control:
• When the PCM detects that the center high mounted stop lamp (CHMSL) in not operating properly.
• When vehicle speed is less than 40 km/h (25 mph).
• When in PARK, REVERSE, NEUTRAL, or 1st gear.
• With low engine RPM
• With high engine RPM (fuel cut-off)
• When vehicle speed is to high
• When an over or under charged battery voltage condition exists
• Antilock brake system/traction control system is active for more than 2 seconds
If the PCM determines that any of the cruise control inhibit conditions are present, the PCM will disengage the cruise control. If the PCM disables the cruise control for an inhibiting event it will record the reason for disengagement in the Disengage Definition data file.

Do you know how to test electrical circuits with a DVOM - digital volt ohmmeter, looking at a wiring diagram for the CC so you know what wires to test , if not your best bet might be to take it to a qualified repair shop .

cruise controls need fully functional units to stay engaged
they include
brake sensor ,
clutch sensor ,
VSS ,
tachometer
cruise switch
if any one has a problem it will disengage
also it only works above a certain road speed or engine rpms

the button only turns the system on
control of the cruise control is by a number of sensors and switches
brake sensor , clutch (if manual) VSS (if auto)
tacho, ECM, Speedo (road speed ) all of which have to word as any one not working will not allow the cruise control to work
run the fault codes and take it to an accredited service center for testing

Check the wire connector that plugs into the cruise control under the hood. Sounds like a loose connection. Remove the and reinsert the wire connector several times to make a better connection. Stepping on the brake pedal disengages the cruise control by a switch on the brake pedal, not the computer.

are you going uphill in overdrive gear . If the speed is lower than you set the crruise control might disengage. ?

Testing the electrical inputs to the control module from the switch . Testing power an ground circuits to the switch . As a professional technician this is how i go about find what is wrong ! Not just replacing parts , that gets expensive. Do you know what a wiring diagram is ,an how to use one to pin point areas to do testing ? Here is a site for free wiring diagrams . http://www.bbbind.com/free_tsb.html Enter your vehicle info. Year , make , model and engine size . Then under system click on Engine , then under subsystem click on speed controls . Click the search button , then on the blue link . You will see all the componets an wiring for the system . Do you know how to use a volt meter ?
Electric Testing Techniques You Need to Know
Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia
96 98 Chevy pickup cruise control not working part 1 test module inputs

Start with the simple and check the fuses and the Stop lamp switch. Check your brake lights, if they're not working, the cruise won't work either. If they're not working, check the fuse for them, if the fuse is fine, then take it into the dealer, there's been a recall issued on the brake switch, so it should get fixed for free.
Cruise Control Disengaged
The powertrain control module (PCM) disengages the cruise control operation based on the signals from the following switches:

* The stop lamp switch
* The TCC brake/cruise release switch
* The clutch release switch, if equipped
* The cruise control On/Off switch

The TCC brake/cruise release switch and the stop lamp switch are mounted on the brake pedal bracket. When the brake pedal is applied, the normally closed TCC brake/cruise release switch opens and the normally open stop lamp switch closes. The PCM detects a low signal voltage on the TCC brake/cruise release switch signal circuit and a high signal voltage on the stop lamp switch signal circuit. When the clutch pedal is applied, the normally closed clutch release switch opens and the PCM detects zero voltage on the CCP switch signal circuit. The vehicle speed stored in the memory of the PCM will be erased when the cruise control On/Off button is turned OFF, or the ignition switch is turned OFF.

The Cruise Control System will disengage when the PCM detects that a driver override function has been active for approximately 60 seconds .

When the Cruise Control System is disengaged, the PCM sends a class 2 message to the instrument panel cluster (IPC) in order to deactivate the cruise control indicator.

Cruise Control Inhibited
The powertrain control module (PCM) inhibits the cruise control operation when any of the following conditions exist:

* A cruise control related DTC has been set.
* The vehicle speed is less than 40.2 km/h (25 mph) .
* The vehicle is in PARK, REVERSE, NEUTRAL, or 1st gear.
* The engine RPM is too low.
* The engine RPM is too high, with fuel cut off.
* The vehicle speed is too high, with fuel cut off.
* The system voltage is not between 9 volts and 16 volts .
* The Traction Control System (TCS) is active for more than 2 seconds .
Thank you for using Fixya and start with replacing the stop lamp switch. Even though the brake light work, it;s been known for that switch to cause your issue. that's way there was a recall for it.

Most cruise controls are designed to disengage when you press the brake pedal. I always mention this first because people tend to try to press the clutch pedal while the cruise control is engaged and this startles them when the engine revs up all the way...

Anyway, to use your cruise control:

1) Press the Cruise control button to on.
2) Drive up to the speed you need to go.
3) Press the "Set/Coast" button.
4) let go of the accelerator pedal

If the cruise control system is operating correctly, your vehicle will continue to travel at the same speed until you either press the brake pedal or you cancel the cruise setting with the cancel button of the cruise control.

Remember: Your civic is not equiped with a radar system for your cruise control, so if you are aproaching an intersection or traffic in front of you, do not expect the car to know it needs to stop. Also, cruise control only operates the accelerator pedal i your car, it is not autopilot, so it will not steer your car for you.

(you think it sounds silly that I am writing this? You should see my friend's car... He thought Cruise control was like autopilot, so he smashed his brand new civic into a tree...)

Happy Motoring!

i had this problem and fixed it. The switch on the brake pedal was slightly off adjustment and was detecting as though the brake was always on, disengaging the cruise control. I pulled it apart and put it back together and made sure it was working ok, now my cruise control is working ok.