Hello and thanks for using Just Answer.I will try my best to help you with your question.
Do the self test for the speed control below. You do not need any special tools to do it. Do the self test and let me know what the outcome is.
I held down the off switch and turned on the ignition and nothing happens
Ok. I doubt it is a vacuum problem.
Check fuses #13 and #28 in the dash fuse box. Make sure they have power when the key is turned on.
Yes fuse 13 and 28 have power going through them with the key on
Yes I have one
Ok, below is the pin point test to follow. It is right from the factory shop manual.
It is a little long, but if you need some help, please ask. It will lead you to what is causing the speed control to be inoperative.
This truck has a 7.3L electronic control. I only see the potentiometer for throttle control. No cable
Sorry about that. The diesel engines are PCM (Engine Computer) controlled.
Check and see if the horn works from the steering wheel, if not check fuse #14 in the engine bay fuse box. If the horn does work, we will need to check the clock spring in the steering column.
We do this by setting the meter to OHMS and with the key off, check the resistance between the GRAY/RED striped wire and the LIGHT BLUE/BLACK striped wire just under the dash on the right side of the steering column. It will be a gray connector. The connector should have 6 wires in it.
Back probe the wires and press the OFF switch, the meter should read 2200 OHMS.
Then set the meter to volts and probe the LIGHT BLUE/BLACK striped wire and press the ON switch with the key turned on, you should get voltage.
With the key on I have 6.5 volts on the light blue/black wire.Press the on button and I get 13.0 voltsI get 2500 OHM when pressing the off button.
Disconnect that connector and check the LIGHT BLUE/BLACK striped wire for power on both connector ends.
You should not have power on that wire till the ON button is pressed.
With the connector disconnected and key on I have 6.5 volts on the harness side.
Thank you. I will check that out