I have 2003 F250 Diesel with 6 speed Manual trans. Cruise light will not come on and cruise does not work. horn works and tail lights function as the should have jumped the connector for the master cy

The first thing to check is the tail lights. The cruise control will not work if any lights are out. Changing to LED tail lights also causes the cruise to not work.

If the switch is replaced,then it can be wiring issue or faulty cruise control board.But as the switch is replaced,get the voltage at the switch tested to confirm the switch is actually receiving voltage.If no voltage received at switch power supply wire then ,apply external 12 volt power to the cruise control switch wire and then see if cruise control comes ON.If yes,then you know wiring is issue.
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On this case, to troubleshoot this problem, there are solved help links. Click the link directly and refer the details to solve this problem yourself, with help of diagrams: ------

Ford ranger cruise control not working? http://technoanswers.blogspot.in/2012/02/ford-ranger-cruise-control-not-working.html

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Horn and Cruise control quit working?

http://howtobyme.blogspot.com/2011/11/horn-and-cruise-control-quit-working.html

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Horn and cruise control not working on Plymouth Grand Voyager?

http://howtobyme.blogspot.com/2011/11/horn-and-cruise-control-not-working-on.html

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Horn and Cruise control quit working on 2003 Jaguar S-Type?

http://howtobyme.blogspot.com/2011/11/horn-and-cruise-control-quit-working-on.html

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Cruise Control stops working, Excessive cranks to start the engine and RPM goes max 2500

http://whoisbyme.blogspot.in/2012/07/cruise-control-stops-workingexcessive.html

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Cruise control stop working on 1994 Ford ranger?

http://technoanswers.blogspot.in/2012/02/cruise-control-stop-working-on-1994.html

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Cruise control not working?

http://schematicsdiagram.blogspot.com/2011/12/cruise-control-not-working.html

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1996 Ford Explorer: Cruise Control Wiring Diagram?

http://schematicsdiagram.blogspot.in/2012/06/1996-ford-explorer-cruise-control.html

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These will help.

Thanks.

On these case,to troubleshoot these problem,there are solved help links.Click the link directly and refer the details to solve these problem yourself,with help of diagrams:------
Ford ranger cruise control not working?

http://technoanswers.blogspot.in/2012/02/ford-ranger-cruise-control-not-working.html

----------- Horn and Cruise control quit working?

http://howtobyme.blogspot.com/2011/11/horn-and-cruise-control-quit-working.html

--------

Horn and cruise control not working on Plymouth Grand Voyager?

http://howtobyme.blogspot.com/2011/11/horn-and-cruise-control-not-working-on.html

------------------
Horn and Cruise control quit working on 2003 Jaguar S-Type? http://howtobyme.blogspot.com/2011/11/horn-and-cruise-control-quit-working-on.html

-------------
Cruise Control stops working, Excessive cranks to start the engine and RPM goes max 2500 http://whoisbyme.blogspot.in/2012/07/cruise-control-stops-workingexcessive.html

----------
Cruise control stop working on 1994 Ford ranger? http://technoanswers.blogspot.in/2012/02/cruise-control-stop-working-on-1994.html

----------
Cruise control not working? http://schematicsdiagram.blogspot.com/2011/12/cruise-control-not-working.html

--------------
1996 Ford Explorer: Cruise Control Wiring Diagram?

http://schematicsdiagram.blogspot.in/2012/06/1996-ford-explorer-cruise-control.html
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These will help.
Thanks.

check your fuses and replace any blown

no engine told 2.3,3.0,4.0 , gas or diesel not told
seems diesel is 1995 and in South america's only.
no vin told.
if it has one, (the speed control version yes, and no speed control NO relay.
bench test the horn yet
or hot wire it in place , actual horn
or ground to the horn is bad as all are that old
dead horn
fuse 8 is first. if blown horn will be dead.
I guess speed controls means CRUISE.?
the steering wheel has cruise there is a relay
if not , such relay is there. proof below. (solid proof)

left side is cruise
right is non cruise opted car. Service manual drawing.

no engine told and matters.
wiring always does on different opted engines.

here is speed control words.? service manual SM.
Modern name is ISC
"On vehicles equipped, the DC motor/idle speed control actuator is mounted to the fuel charging assembly. This component controls the idle speed, including such functions as high cam rpm, anti-diesel shut off, dashpot and pre-positioning the engine fuel charging assembly for restart. This control actuator is driven by the EEC-IV system, which includes an integral idle tracking switch".

bad fuse F8 OR WRONG SIZE USED, AMPS WRONG.,MISSING
HORN FUSE IS 20AMPS IIRC.
bad slip rings
bad horn switch.
bad relay if fitted
both horns bad.
both horns 1 ground are rusty , horns work benched tested

GOOD LUCK

Hi, assuming you have cruise controls on the steering wheel, I would say your clockspring has failed. The contacts for the horn must be crossed with the cruise contacts. Replacement requires removal of the steering wheel (special tool) and airbag, etc. Please let me know if you would like instructions.

Does the horn and cruise control work? If not it is likely the clockspring located underneath the airbag in the center of the steering wheel.

Do you have a multiswitch on this? Cruise not working would indicate that to me. The horn you got working, then, with the clock spring wiring.

Check to see if the cable for actuating the cruise underneath the hood at the throttle body is broken or not.

Sounds like a bad clockspring