I have a 2002 3.7L KJ. The cruise control on/off switch "works" as I can see the green cruise light illuminate on the cluster. However, the "set" switch does not set the cruise.

I'm hoping someone here can point me in the direction of a few mechanical and electrical test points to troubleshoot the cruise control system. The chilton/ hayes type books at the public library are of no help so far, and with April 17th approaching fast, I can't afford a factory service manual.

I have checked all associated fuses and have applied dielectric grease to all associated electrical plugs. I just don't know which wires to probe. Add to the fact I have to be doing ~40mph to probe said wires and im going nuts here.

I hope someone can help.

Another area to check would be vacuum hoses - the system runs on vacuum so any disconnected hoses could lead to a similar situation. This is from my FSM:

DIAGNOSIS AND TESTING - ROAD TEST
Perform a vehicle road test to verify reports of
speed control system malfunction. The road test
should include attention to the speedometer. Speedometer
operation should be smooth and without flutter
at all speeds.
Flutter in the speedometer indicates a problem
which might cause surging in the speed control system.
The cause of any speedometer problems should
be corrected before proceeding. Refer to Group 8J,
Instrument Cluster for speedometer diagnosis.
If a road test verifies a system problem and the
speedometer operates properly, check for:
² A Diagnostic Trouble Code (DTC). If a DTC
exists, conduct tests per the Powertrain Diagnostic
Procedures service manual.
² A misadjusted brake (stop) lamp switch. This
could also cause an intermittent problem.
² Loose, damaged or corroded electrical connections
at the servo. Corrosion should be removed from
electrical terminals and a light coating of Mopar
MultiPurpose Grease, or equivalent, applied.
² Leaking vacuum reservoir.
² Loose or leaking vacuum hoses or connections.
² Defective one-way vacuum check valve.
² Secure attachment of both ends of the speed control
servo cable.
² Smooth operation of throttle linkage and throttle
body air valve.
² Failed speed control servo. Do the servo vacuum
test.
CAUTION: When test probing for voltage or continuity
at electrical connectors, care must be taken
not to damage connector, terminals or seals. If
these components are damaged, intermittent or
complete system failure may occur.

_________________
Kevin
AD5VG
Just another red Jeep in the world...
L.O.S.T. #KB051963

Have you checked the cable on the throttle body linkage? Mine popped off on me before, it just pops right back on.

_________________
'03 KJ Limited, 3.7l: K&N drop-in, D.I.Y intake tube, clear corners, Hella 500's, Flowmaster 50 SUV

Thanks for the suggestions so far, I spent most of the weekend testing it.

The "set" switch does make contact. I took apart the steering wheel and tested all the switches for contact. They all work properly.
There are no vacuum leaks. I tested several connections with a hand vacuum pump. The cruise vacuum unit works smoothly as does the cable.

I have read some other threads that suggested some brake control unit. If that were acting up, wouldn't I have brake light problems?

I also read about bad clock springs. How many wires are on the clock spring? My horn still works so there is contact in that part of the clock spring.