Broken Cruise Control

My cruise on my '90 4.0 5spd just stopped working one day. Anyone know how to test cruise servo's and control modules? I'm pretty sure my wiring is okay. There is a switch on the clutch that I jumpered because I thought the switch might be bad. My vacuum canister is holding vacuum. The speed sensor is plugged in. Ive checked and re-checked everything, the only thing im unsure of is if my module or servo is bad. I have three modules and two servo's from junk yard runs and such. Lemme know. Thanks
Ecarlcl

Time for a FSM or equivalent. Do a search of FSM. There is a link to a sight to down load one. You might get by with an 88 FSM as 88-90 are nearly identical.

sjx40250 is correct about using an FSM and the wiring diagrams to track down this sort of problem. Just "hanging parts" until you fix the issue make take a LONG time, and cost you a bunch in stuff that did NOT need to be replaced.

Just FYI, the steering column in the older XJ's is a GM-supplied item. That means it uses the GM type cruise control switch. These switches have a long thin wiring harness that travels from the turn signal stalk all the way down the steering column, and mates up with another harness under the dash. They are prone to developing opens (broken wires) in this thin harness.

Check and double check the brake release switch located on the brake pedal, mine was unhooked and was an easy fix

jerrywagner said:

Check and double check the brake release switch located on the brake pedal, mine was unhooked and was an easy fix

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Ive looked at that, the brake lights work on both sets of terminals so I assume its good.