Hoping someone has been through this before and can make a few suggestions:
My truck is a 1995 F350 crew cab, 460, automatic. Bought it used. It was a complete plain Jane. Nearly (or maybe literally) no options. I bought a used cruise control assembly and a horn button assembly with the cruise control switches, watched a couple videos, and installed the parts. The cruise does not work. By "not work" I mean that it shown no sign that it even exists. Nothing that I noticed changed on the dash, although the dash lights are so dim I might have missed something. It doesn't hold at any speed and doesn't act like it will ever try. I found which fuse powers the cruise control and checked it. Fuse is good. I guess there is a good chance the cruise control assembly is non-functional. I haven't pulled the horn button assembly off to check to see if the buttons all work. Can do that next, but was hoping someone out there has been here before and has some idea what is likely wrong.
Thanks.

 

There's no dash indicator for the cruise control. The only way you know it's engaged is by the accelerator pedal moving without you.

Do you have LED lights in your brake light? The CC computer hates those.
You'll need to get a multimeter and start checking the pins on the harness side of the CC servo connector. If you don't have a multimeter, then you're shooting in the dark.
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You have a clutch switch working too?
You have all the speed control parts on there?

 

No idea if this has anything to do with your problem or not, but one of my proudest moments in electrical diag was from a similar issue.

Bought a '92 F-150 Custom. Wanted cruise. Installed horn pad, module, and vacuum actuator thingy. No cruise. As you put it, no indication it was even trying. Checked all the dumb stuff like fuses, brake lights. etc., no problems found. Borrowed an FSM from a friend, and I get to the part of the procedure where it has you test for something in the blue wire inside the column, at the sliding contacts- and the thing I was looking for was there (forget what it was, this was 9 years ago). Testing for that same thing on the top side of the steering wheel, it wasn't. Horn pad itself worked fine. Sliding contact worked fine. I said to myself "[redacted], it's almost as if the electricity is disappearing inside the steering wheel". If true that would be very odd, so I sat on it for a few hours while doing something else. Came to the conclusion that I wasn't crazy, the electricity was indeed disappearing inside the steering wheel. So I used a blowtorch to melt off the plastic on the thing that holds the sliding contacts, that the wiring disappears into- and found that one of the sliding contacts' wires wasn't soldered to the harness connector before they overmolded everything with black plastic goo. Soldered it on, went for a test drive, cruise worked great. The plastic I removed wasn't visible with everything assembled, so I did nothing to cover it up.

Best I can figure, whenever they have a steering wheel that fails QC, instead of throwing it out they mark it somehow and make sure it winds up in a base-trim truck without cruise.

 

Thanks for your input. No, I do not have LED lights anywhere. I do have a multimeter. I will go through everything this weekend using the Fluke and see what turns up.

 

I have an automatic. No clutch switch that I know of. You asked if I have all the speed control parts installed. I think I do, but I only installed two components, and that is all there were to install on the couple videos I watched. One is the steering wheel horn pad with the buttons. The other is an assembly consisting of some kind of module that goes on driver's side upper inner fender. Has a receptacle for a multi-pin electrical connector which I did connect up. Also has what looks like a cable that runs behind the top part of the engine over to the throttle control on the RH side of the engine. As I remember, that was it. Is there more?

 

There is a component Ford calls an "amplifier" that goes inside the dash, pretty close to where the warning buzzer is (where the bulge starts to the right of the driver foot well, but left of the ash tray).

 

1993 and up trucks didn't have a separate amplifier. Amplifiers were used on vacuum operated cruise control previous to 1993. In 1993 and up trucks, the amplifier(=computer) is integrated into the electric servo in the engine compartment.

 

Yes there is...

There is an input that is fed through the Brake Pressure Switch mounted on the master cylinder for 1994 and up trucks. This is the infamous fire starter that prompted a massive recall on millions of Ford vehicles in this era. Below is a diagram of the Speed Control system pre-recall and the Brake Pressure Switch location. The recall added a dedicated fuse for the BPS circuit. The Speed Amplifier is expecting +12 VDC on the Brake Pressure Input circuit (Pin 9) when the brakes are not applied.

 

I had this problem a few years ago and with no testing I just went got that pressure switch and all was good ,it tells the Cruz to cut off when brakes are applied and when its bad it thinks breaks are being applied ,my problem now is its been a few years and it not working again and I figure its that aftermarket switch gone bad

 

Yes, test this switch and any related fuses in the recall jumper wires if that was done.
Even if you have a red switch that isn't leaking you should replace it with the new replacement switch and proper pigtail adapter, which will allow you to eliminate the "add on fuse" recall "fix".
Motorcraft SW6350


I have had several of the red switches go bad with no external leaking so you should test each side of the switch for proper operation.
If this switch breaks continuity, whether it is red or black, it would keep the speed control from operating.
Testing is as simple as using a test light on either side of the switch to see if power is present on both poles.

 

Dang, I should know that. Thanks for catching.