My cruise stopped working on my 1991 GMC Sierra 1500 while I was driving. I did a continuity test on the brake switch and it works fine. Any ideas?

check all fuses!

check the brake switch on the upper arm of the brake pedal, if its bad your cruise control won't work because the truck thinks your pushing the brake pedal. I had the same problem in mine, it's a $30 part that takes about a half hour to fix

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.

The brake light switch can prevent the cruise from working.
On the cars there is a 5amp cruise fuse so I would think there is one for trucks too.
You may have to get a shop manual to get the diagrams to check the circuits and have a test procedure.

If you got a scanner,not a code reader, and you
get yourself a wiring diagram,it should be a
fairly easy fix

have you tested your brake switch,it could be your brake switch.looks like you have done about everything else.

Wiring, schematic, electrical diagrams, fuse diag, error codes, torque settings etc are basic contents of these online books they have here on this website www.reliable-store.com I have attached. Must check it out

May want to look at replacing the wiper circuit board.It is located on the firewall adjacent to the wiper motor and has a some what square black cover with 3 torx screws and wireing harness pluged into the side.We had a truck that every time you washed it the wipers would stay on until it dryed out.You can try removing it and spaying it down with contact cleaner just watch the brease on the two contact tips.Well hope this helps.

adjust brake switch on drake pedal for cruise .

normally the brake switch is the issue with these trucks. it is located under the dash where the brake pedal meets the linkage to the brake booster.