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Thread: Help please

  1. #1
    Registered User
    Name: Patrick


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    Help please

    I replaced the cruise control switch on the master cylinder seems to still be shorting out any ideas?

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  2. #2
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    Name: Chuck


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    What do you mean by shorting out??? need more information!!!! that switch is a normally closed switch, meaning the contacts are closed in normal operation when you apply the brakes it opens the contacts to shut down the cruise control. If you unplug the switch the cruise will not operate if you connect the two wires and everything else is ok it will operate. Under normal operation it supplies battery voltage to pin 9 of the speed control sevo through a 5 amp fuse (f2.15) also requires battery voltage pin 7 that is supplied from a 15 amp fuse (f2.5) I believ both fuses are in the central junction box, under the dash. You can acess a self test of the cruse control using the switches. with the key off press andd hold the off button on the cruse and then turn the key to the on position (NOT START) , the speed control light should flash once that it is in the diag. mode. five additional flashes at this time indicate a bad module. release the off switch within five sseconds push the remaining switches in this order on, resume coast and set/acccel the light will flash as you push each button indicating the buttons ar ok prees each switch as the light goes off if the light flashes after the last button the system passed if after a few seconds there are multaple flashes count them and let me know ther is a chart to follow. if the test is passed after a second delay the servo wil activate and you can see the throttle actualy move and open. return the switch to off to stop the test.

  3. #3
    Registered User
    Name: Chuck


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    You can also check pin 4 on the servo should be no power there normal operation, it should get battery voltage when you depress the brake pedal.

  4. #4
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    Name: Patrick


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    I haven't had time to do what you suggested yet buy after I replaced the switch and reconnected the battery the fuse still keeps blowing as of the new switch is bad

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  5. #5
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    Name: Chuck


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    OK now i understand your problem, Try leaving the switch unplugged and see if the fuse blows or stays if it does not blow then try unplugging the large plug from the servo and then try plunging the switch back in. Then let me know what goes on. I have the OE Ford wiring diagrams and can possibly help you, I don't have the book in front of me right now, it's down my garage, but try what I said, that will help to narrow down where to look. I'll be around all weekend if you need help. From what you are saying the self test may not be necessary, although it is very easy to do. It will probably either indicate a bad servo or maybe jut a bad BOO switch. You will have to find out why that fuse is blowing first i believe.

  6. #6
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    All the buttons work and the light flashes 3 times after the last button is pushed. Disconnected the servo and the top pin looks like it's fried

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  7. #7
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    Name: Chuck


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    So the test shows 3 flashes which proves what we already know, the problem is in the deactivation switch circuit. which sends us to pinpoint test H basically we need to check wire at pin #9 black wire with a yellow stripe this wire with a good fuse should have battery voltage pin 10 the all black wire is the ground circuit. You measure voltage between the two wires. What color wire has the burnt pin so i can determine what circuit is damaged.

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