Brake warning light on.

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powerjen

Member
Joined
May 25, 2006
Posts
16
Hi,

After getting all the lights swapped over for UK registration (which it has now happily passed)!  ;D We now have the brake warning light permanently on, on the instrument panel. We have a 92 National RV on a Ford 350 chassis.

Keith has bled the front brakes after finding them locked on after it had been stood for 10 months. the following week, when we drove it 40 miles to get it registered Keith said that the brakes seemed fine, other than once early in the journey where he thought they were a bit vague, but came right back.  Keith cut various wires trying to figure out which ones he needed to change the lights around.  Although all were reconnected.  We have no experience of brake problems so any help or ideas would be gratefully received.  Could the 'vagueness' have been a one off and the warning light a reaction to a wire that has been cut or is it something that needs looking at and what could it be?  ???  There is plenty of life left in shoes and discs.

Thanks in advance.

Jen
 

King

Well-known member
Joined
Jan 30, 2006
Posts
354
Location
MA
Hydraulic braking systems on all modern vehicles have front/rear separation that is intended to provide some braking when a single brake line or wheel cylinder fails.  It uses a small shuttle piston with front on one side and rear on the other.  If the piston is moved too far in either direction, the brake light comes on.  After bleeding the brakes, it is usually necessary to re-center the piston.  The vehicles I have owned, the procedure is to depress the brake pedal hard several times until the light stays off.
Art
 

John From Detroit

Well-known member
Joined
Apr 12, 2005
Posts
25,261
Location
Davison Michigan
That light also does double duty, Not only does it show a problem in the hydralic brakes, it also indicates when the parking brake is applied.  It may also indicate a problem with the parking brakes (of course driving with them applied is a problem)

If your rig uses a foot pedal operated parking brake try this as well.

Pull the brake release lever, and hold it, while holding it use either the toe of your shoe or your other hand to PULL the parking brake pedal up till it stops.. If this turns off the light your parking brake cable is jamming and needs to be replaced or at the very least exercised,  I've never seen one recover though so replacement is likely the only option
 

powerjen

Member
Joined
May 25, 2006
Posts
16
Thanks guys. 

We have a hand operated parking brake and it seems fine.  We haven't ventured under the bonnet to see if there is a little piston as you mention King, but at least we are pretty convinced that it is a result of the brake bleeding so puts our minds at rest.

Thanks again.

Jen
 

Karl

Moderator Emeritus
Joined
Mar 3, 2005
Posts
5,154
Location
Elkhart Lake, WI for the summer. Work at Road Amer
Jen,

You won't actually "see" the piston; it's part of the master cylinder assembly. Another posibility is a low level of brake fluid in the reservoir. Make sure it has enough in it. I would also suggest a complete bleed of all wheels, starting with the one farthest from the master cylinder, the next farthest one next, and so on. Use only a new, unopened can(s) of fluid as previously opened cans can and will absorb moisture, reducing its' effectiveness.
 

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