MGB Question on the brake warning light for 78 MGB

[Jerry]

A friends MGB has the Brake light on all the time. This is after the engine was removed for rebuilding. The light stays on and I think it is the connection that is bad. For those of you that that have this switch, how often does the switch itself go bad vs a connection problem itself? The wires and rubber are very old and brittle, so I suspect the connection.

So, is the switch just testing for fluid in the resevoir? If so, will an ohm meter show that the two leads are connected as long as the fluid is in the reservoir?

Jerry

 

[LarryK]

Is the light on one or both? Check lights for proper bulbs and wiring. Use voltmeter and check hot side of foot brake switch. Is this on with key off? It is an old car anything can go in an instant especially if banged or bumped. Crusty wires can be a problem too!

 

[Jerry]

Sorry, I meant the Brake warning light on the dash is on all the time. Rear brake lights work fine.
Jerry

 

[maynard]

Assuming the brakes are fine, unscrew the switch (on the master) step on the brakes a couple of times and screw in the switch.

 

[fixitright]

My understanding of the break warning light is to alert the driver that some part of the break system has failed by comparing the pressure in the front breaks to the pressure in the rear breaks if that pressure differs much it would indicate a problen in one or the other systems. If the warning light is on continuiously it will mean it is faulty and is stuck in one or the other position it should return to off when the brakes are not in use

 

[LarryK]

It also warns of low fluid if wired and parking brake set. The differential valve will not reset itself unless the pressure equalizes by bleeding or leaking or luck. The light itself in the older cars will not go off on it's own unless pressure, level and handbrake are back to normal. Maybe there is a short in the wiring from reinstalling engine and crushing wires. Wires were said to be old and switch was questionable.

 

[DrEntropy]

In my experience, too many times the handbrake switch or circuit has been the culprit.