reinstalled the cruise control servo, and the cruise control is not working?

I would start by checking the brake light switch adjustment because this will cause the cruise control not to work. Here are the system wiring diagrams so you can see how the system works and where to check for power and ground.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the images (below). Please let us know how it goes

Thanks Ken. I want to update you. I was looking around for the brake switch you mentioned, and noticed that the wire for the cruise, from the turn signal switch, was cut and not even plugged in. (Face palm). So, I replaced that, but still nothing. So, back to square one. I found the brake light switch, it has 2 plugs in it, and seems to be working. The brake lights come on :) haha on the same bracket is a black switch as well; is that for cruise or something else? How do I check them for proper adjustment/functionality?

Yep, one is for the brake lights and the other is for the cruise control. If the brake lights are coming on the switch is working. But to test the cruise side use a voltmeter on continuity and when you press the brake pedal it should connect.

This guide can help:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go over this guide and get back to us.

I tested it this morning, and here’s what I’ve found while pressing the brake pedal:

- No readings on the gray plug at all. The gray wires feed into the black hose that’s connected to the black brake switch.
- With red lead on orange and black lead on white: 3.89 ohms.
- With red lead on white and black lead on orange: -2.46 ohms.

You need to test the switch with the wiring connectors disconnected. Please let me know, test while pressing the brake pedal and not pressing the brake pedal as well.

Okay, tested the switch with both plugs disconnected. Bottom plug (orange/white), I got 1 with no brake pedal, and 0.00 with brake pedal, on both combinations of red and black leads. On the top plug (gray), I got the opposite, 0.00 with no brake, 1 with brake.

You tested through the switch, correct? let's go over the vacuum lines to make sure they are correct. Check out the images (below). Please let us know what you find.

Yes, I disconnected the plugs from the white switch and touched the multimeter leads to the switch prongs directly.

Attached are pics of my vacuum setup currently. Manifold vacuum > T fitting > one end to the brake booster, one end to check valve > one end to vacuum accumulator ball, one end to another T fitting > one end to climate control, one end to cruise control servo. Other outlet on servo goes into a black hose that goes through the firewall to the brake pedal area (I believe.)

Yep, the vacuum lines look good, you might have a bad/defective servo. But I do remember that the switch stock (blinker handle) would break the wires just outside of the switch. I think I found the wiring diagrams for the cruise control, but it is a little hard to read.

Thanks Ken. Is there a way to test the servo? Or the power going to the servo?

I am sure there is, by looking at the wiring diagrams I would test the signal from the cruise switch and the power and ground to the system. Did you replace the turn signal stock? They had a high rate of failure.

Hi Ken, I wanted to follow up with this thread. A long story, but I found that the optical speed sensor that mounts to the rear of the speedometer was disconnected. I re-mounted that and the cruise started working! Hooray! However, the truck will “jerk” when cruise is engaged, as if trying to hold speed, it gets too much acceleration, and then too little acceleration. Any thoughts on that?

Good job getting it fixed. I am not sure what you mean by "jerk"? Do you mean the engine will misfire?

No, the engine fires fine; it's like if someone is pushing the accelerator pedal then releasing, then pushing again, and releasing again. The truck will surge back and forth with the acceleration changes. It will hold the set cruise speed, but it's not smooth at all.

Does it fell like the cruise control is "hunting"? If so this is caused by the cruise control unit, can I ask if the speedometer is working smoothly?

Yes, the speedometer is working great; a few MPH slower than actual speed, but it operates smoothly.

It sounds like it is the transducer itself. Do you have another one you can swap out to see if it makes a difference?

Are you referring to the Servo? That attaches to the carb and vacuum lines. Or something different? I'm not sure what the transducer is.

Yes the servo, the cruise control head. That is the only thing that can make the cruise control hunt.

Confirmed: Servo is all over the place. I stuck a GoPro under the hood and got this footage. I have a used one I can try swapping out, but it’s a pain to get those screws back in! :)

Nice work, this is a common problem with the cruise control hunting problems. I am glad you figured it out. Use 2CarPros anytime, we are here to help. Please tell a friend.