Brake light pressure switch
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Elder User
Joined: Jul 2006
Posts: 532
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From: Athens, GA, USA
Originally Posted by ALBUQ F-1
Are you using a hydrovac? or remote booster? I don't see how the pressure would be any different otherwise.
FOR SURE -- NO compression fittings!! Hardware store brass fittings are also likely to be suspect.
FOR SURE -- NO compression fittings!! Hardware store brass fittings are also likely to be suspect.
If it were purely a pressure problem, the brake lights would never work. My problem is that they work with a new pressure switch for about 2 weeks and then, nothing. Checked the switch with an ohm meter while my wife operates the brakes and it doesn't close. I have the correct voltage to the switch.
It acts like the internal mechanics of the switch are breaking down.
Fleet Owner
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From: NM
Originally Posted by doug51f1
The pressure is "boosted" i.e. just higher in the brake line than in the master cylinder because the line is so much smaller in diameter than the cylinder.
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Elder User
Joined: Jul 2006
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From: Athens, GA, USA
Originally Posted by ALBUQ F-1
Not true, the pressure is exactly the same everywhere in the system.
Fleet Owner
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From: NM
Originally Posted by doug51f1
Hmmmm......what was I thinking? I was confusing pressure with volume. Well then, putting the switch in the brake line instead of the master cylinder really makes no sense.
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There is a good reason they no longer use pressure switches for brake lights. I would sugggest installing a mechanical switch that will be activated by the moving of the brake pedal.
Also whether or not the switch is used with 6 volts or 12 volts is not the problem. The switch doesn't care. Adding a relay would only seem to add another potential component to fail. A relay should only be needed if you have so many lights it exceeds the rating of the switch. The standard two or three lamps should not be a problem.
Also whether or not the switch is used with 6 volts or 12 volts is not the problem. The switch doesn't care. Adding a relay would only seem to add another potential component to fail. A relay should only be needed if you have so many lights it exceeds the rating of the switch. The standard two or three lamps should not be a problem.
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Joined: Jul 2004
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From: NM
Originally Posted by barbsbuddy
There is a good reason they no longer use pressure switches for brake lights. I would sugggest installing a mechanical switch that will be activated by the moving of the brake pedal.
Also whether or not the switch is used with 6 volts or 12 volts is not the problem. The switch doesn't care. Adding a relay would only seem to add another potential component to fail. A relay should only be needed if you have so many lights it exceeds the rating of the switch. The standard two or three lamps should not be a problem.
Also whether or not the switch is used with 6 volts or 12 volts is not the problem. The switch doesn't care. Adding a relay would only seem to add another potential component to fail. A relay should only be needed if you have so many lights it exceeds the rating of the switch. The standard two or three lamps should not be a problem.
Doug, why don't you hook up a test lead from the battery (+), with a 10 amp (maybe 15) circuit breaker in it, and connect that to the wire heading off to the brake lights. See if it pops the breaker, smokes, or there are any other dramatic results. Leave them on for 5 minutes, see if there's anything getting warm...
By the way, you do have stock brakes, don't you? No booster?
Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
Originally Posted by doug51f1
I'm running a stock Master Cylinder with the original style pressure switch for the brake lights. I have had to replace the switch three times in under three months. Has anyone else had this problem?
I wouldn't think that the amperage is too high on the contacts, since my truck is 12 volt (half the current/twice the volts).
I wouldn't think that the amperage is too high on the contacts, since my truck is 12 volt (half the current/twice the volts).
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Elder User
Joined: Jul 2006
Posts: 532
Likes: 1
From: Athens, GA, USA
Originally Posted by ALBUQ F-1
Doug, why don't you hook up a test lead from the battery (+), with a 10 amp (maybe 15) circuit breaker in it, and connect that to the wire heading off to the brake lights. See if it pops the breaker, smokes, or there are any other dramatic results. Leave them on for 5 minutes, see if there's anything getting warm...
By the way, you do have stock brakes, don't you? No booster?
By the way, you do have stock brakes, don't you? No booster?
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