in an older vehicle, people dont often take the time to fix luxury things like cruise control, and i know it happens to be a common thing for this model to fail.
I fixed mine, and it didnt take a whole lot of effort, so i figured i would share my experience to hopefully benefit others. Its too dark right now to take pictures, but i will do that tomorrow and upload them, but for now, i will give the text instructions.
This is based on a 1987 3.9L, but i assume most first generation models should be remarkably similar.
The likelyhood of any single step fixing this is low, such as cleaning electrical connections, this is more of a preventative measure, just follow every step, no need to check it every time.
First step, is to pop the hood, obviously. On the right side, if facing it, will be a device, i dont know its name, but it is circular in shape, has one vacuum hose, an electrical connection, and two mechanical linkages.
This is the main cruise control device. It is activated by the vacuum hose, and causes a cable to pull on the throttle.
The vacuum hose is connected to a pipe with many more hoses that is mounted on the cabin side wall, battery side in the engine compartment. When the brakes are depressed, or the transmission placed in neutral, or any number of things, it causes this to disable the cruise control. All of this happens through this pipe. Check all the hoses for obvious signs of damage, anything that is loose, etc. I used a hand-held vacuum pump to check things, and found a lot of leaks, and one hose that went no-where, it was broken, and the other half gone from existence. It is not a horribly fragile system. The main thing is that you want the connection with the brakes to be good. It doesnt have to hold a vacuum, mine didnt, but it does have to be connected solidly, and not be cracked. This hose is the one on the far left, and the biggest. If there are any random, open hoses, seal them off, completely air tight. You could remove the hose and plug the connection to that main pipe, or fill the hose with superglue. But it has to be seperated from the rest of the system, otherwise it will cause problems. The only ones i have found to be important are the brake hose, and the one connecting to the first device. In an effort to increase gas milage, i shift into neutral often, so the transmission hose is important for me, but im not sure which one it is. Mine is functioning.
Turn the key to accessory and engage the cruise control. Listen closely as you engage and disengage, you should hear a click. This is good. It means that first device we talked about is working. If you dont hear a click, you could have a bad electrical connection. The wires in the steering wheel take quite a beating, but it is a hassle to check this, which is why i left it til now.
You will need to remove the large plastic piece that protects the steering column and wires underneath. Take a look at the pictures posted the day following this one for a better explanation.
There will be a connector, again, just look at the pictures. Check it and make sure the wires and connector are not damaged, and that everything is clean.
Check to see if you can hear that click previously mentioned. If you cant, you may have to remove the cover to the turn signal/cruise control/wipers. When i removed mine, i never bothered to put it back on, so i have a metal rod sticking out. It still functions fine though.
Take the four wires, well, the only wires, and touch them all together simultaniously, do you hear a click now? If so, you will likely have to rig it up like mine, as your switch is bad. If you dont hear this click, check the vacuum hoses again. Post anything you find suspicious, and i will check what it does with my vacuum pump and get back with you. No sense in wasting your money to buy one for a non-essential repair.
If you are sure that the hoses and main pipe check out, then it may be some kind of glitch with the brakes, causing the vehicle to think that the brakes are depressed, therefore, not engaging cruise control. Ensure that you are getting a solid electrical connection accross all the wires. If it still doesnt work, then i am sorry, but that is out of my league.
What i did was basically guess and check to find out how to turn on the cruise control, and how to set it. Details follow in the next post. You will need two on/off switches. These are like $1.50 at walmart. You will also need some electrical terminators to fit the switches. Again, a pack of more than enough is like $1.50. Pictures of them can be found in the following post. I secured them to the left of the steering wheel with some double-sided adhesive. They have held together for a couple months now, but i intend to freshen it up a bit soon.
Basically, you need to find whatever is causing that clicking noise to not happen, this could be vacuum hoses, electrical connections, or a bad [insert name of first device discussed]. Play around with it, clean things, plug up leaky things, until you hear that click. Now you want to make a switch to activate it. There are many options, and i will post a wiring diagram, but i will explain in the following post, in detail how i did mine.
One annoying thing about this, is that you have to go a few miles per hour over what you want to set it at, 45 is 49, 50 is 55, 55 is 61, 60 is 67, 65 is 73, you get the point? Its just something you have to get used to. Be thankful you didnt change your real wheels to a smaller size and are too cheep to update the speedometer cable, i have to calculate, based on speedometer reading + exponential growth, my actual speed, then calculate what the set-point of the cruise control is. If i want to set at 65, i wait til i read 75... That is an example. 45mph would be set at a reading of 50. 50 would be set at 57.
So sorry it took so long to get these pictures posted.
http://s678.photobucket.com/albums/v...asymac79_2009/

 

Damn that is a nice post! Good job.

 

Does anyone have a list of the cruise control components? Thank you.

 

*dry* It depends on the year and sometimes the motor.

RwP

 

Good point. In my case i have a 1989 Dakota Sport with the 3.9L V6. Any guidance would be appreciated.

 

I'm not sure which design was used for 1989; you may need to pick up your factory service manual to make sure.

But.

1) Control stalk same as my 1988 - replaces the wiper stalk, has a On/Off/Resume/Set set of switches.

2) Different brake light switch (to add a "Drop Cruise" switch to the brake pedal)

3) Servo under the hood - for 87 and 88, and possibly 89, the servo includes the controller; so

3a) Cable from transmission or transfer case to servo.

3b) Cable from servo to speedometer

That's because the 87/88 design was self-contained.

4) Wiring to passenger compartment - 3 wires into the bulkhead fitting.

5) Wiring inside passenger compartment

6) Cable from servo to throttle body, and any additional linkage needed there.

If they had changed from the stand alone design to the integrated design for 1990 (by 1991 they had), then there's the wiring from the servo to the ECU, and the wiring goes from the switches inside to the ECU. That, I do not have, since I don't have a 1989.

RwP

 

Very helpful. Thank you!

 

I will say again, be sure to use the factory service manual for a double check.

By 1990, the cruise controller was in the main ECU; that may have been done in 1989, but I Just Do Not Know.

RwP

 

Heh. I forgot the PDF earlier.

Here it is.

RwP

 

Thank you!