I just purchased a 1994 ford thunderbird and two hours after taking it off the lot the cruise control and speedometer stopped working

the gas filters are clogging up and need replacing or trash on your fuel pump screen.

dirty fuel filters need to be replaced

speed sensor.

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

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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

----------
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.

If the speedometer and odometer are not working the problem is usually lack of signal from the transmission speed sensor.
But if the cruise control works and the speedometer does not, my guess would be a problem inside the cluster.

if the vehicle speed sensor in the rear end is the same as the lighter duty f series they are very vulnerable, they run right above the large gear in the main drive of the rear end gaging the speed off this gear any metal chip or anything foating in the rear end can get grabbed by this gear and hit the sensor then it is ruined very common in fords. your can check the part at autozone or similiar store for lighter duty trucks it is 19$ and very easy to get to right on top of the rear end. If this is the problem id have the gear oil changed and check for debris in rear end to keep this from happening again. good luck

U WILL NEED TO REMOVE THE SPEEDOMETER AND SEND IT OUT TO A FORD SPEEDOMETER REPAIR CENTER.

check the od switch to make sure its working then check the grey conector to the tranny under the car if it looses its conection your car will loose 3 4 5 also check your computer on the passenger side and make sure its fully conected if the clip comes loose the tranny is the first to stop working

try replacing speed sensor located on taillshaft or side of transmission. could be a likely cause if speedometer quit.