96 Ford F350 brake light issue

zuk88

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My brake light on my dash comes on at times and fades away turning off the cruise. I've replaced that sensor at the end of the master cylinder and got the updated wiring harness and it helped and the light was off for more than two weeks until this morning. Could the next step be replacing the master cylinder level sensor or is there something else I should look for?
 

hlb3

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Does it only happen when the Cruise is on?

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TrikeKid

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The sensor on the end of the master is just the cruise control cancel switch (Brake pressure applied switch). If you've got a red brake light on and the master is full then yeah, bunk level sensor is most likely. If it only happens with the cruise then there's something wiring wise wrong or it may be something in the cluster shorted.
 
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zuk88

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That's what I was thinking next. I read about the old cruise cancel switch shorting out and causing a fire so I figured that would be good to fix and the dash light seemed to go away but decided to come on again but hey......no fires under the hood.
 

Murkman

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There is a sensor in the rear end that reads a tone ring. Try that one. My 91 did id and thats what they replaced.
 

TreeClimber

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I would think, that the Ford Dealer would have a scanner that can tell you what sensor is triggering that dash light.

Sometimes, it's cheaper to pay for diagnosis, than to throw parts at a problem.
 

zuk88

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What did ya do to fix it??? got a motor home that needs the cruse mod!!!:redneck:

Ford had a recall but I didn't take mine in. I called Bickford parts department and it was under the master cylinder brake fix kit, a different looking sensor and updated wiring harness.
 

zukkev

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The red brake light is not tied into the OBDII system. Also, the Rear wheel speed sensor in the rear diff will not turn on the red brake warning light, it will, however turn on the ABS (or rear ABS if only RABS equipped) light.
Go after the level sensor, after verifying the level is full. If the fluid is very dirty, you can try cleaning out and flushing the Master Cylinder. I have had some success with just this...Lots of sediment in the bottom of the M/C can throw the sensor off...IF you have lots of sediment, it might be a good time to just replace it as an assembly.
 

zukkev

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The other possibility is maybe the parking brake switch is coming on due to the pedal "relaxing" and triggering the switch to turn on the brake light. I have seen that as well...
 

zuk88

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The e brake pedal travels down almost an inch before it comes on. The fluid in the master was really dirty so I took out as much as possible with no luck. May have to replace the reservior with a new sensor.
 

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