Replacing Series 3 brake light switch

[sllim1946]

This is a fairly easy task but I thought i'd write it up anyway.

Access to the switch is very easy once the front wheel has been removed. Lift up brake fluid reservoir  pressure plunger and lock up with mole grips or similar.

Disconnect the wires from the switch and remove it using a 24mm open ended spanner (An 15/16 AF will work just as well at 24.2mm).  Replace the copper washer and attach the new switch. Before tightening fully, release the fluid reservoir  pressure plunger and allow fluid to flow from switch to avoid possibility of air in the system then fully tighten.

Connecting wires will need to have connectors cut off and replaced with modern 6mm spade type – use blue insulated ones. As wires are quite short cut just above the original connectors.

Brian Mills

[lancianut666]

Good tip about bleeding the fluid from Brian. New brake light switches are available from the Appia Consortium.
Clarkey

[Spider2]

Is there a link to Brian's tips about bleeding the brakes. I have just replaced the seals in the master cylinder and changed the pressure switch but cannot successfully bleed the brakes. I have about 80% pedal travel before any resistance is felt. There appears to be no air in the system and the last 20% of pedal movement does lock up the drums. This is on a series 2

[lancianut666]

Sounds like you might have problems with the reservoir. If the seals are poor the pressure to bleed the brakes will not be maintained and you will find it tricky to get all the air out. As a rule when you pull the plunger on the top of the reservoir up it should stay up and you can then bleed the brakes as plunger is a piston acting down on the brake fluid via a spring and some brake seals. It might be the master cylinder bore is worn or the flexible hydraulic hoses are weak.
The Appia Consortium has most of the seals you might need as well as new hoses.
Clarkey

[Spider2]

The piston in the reservoir does not stay up so bled the brakes the old way by a friend pumping the brake pedal. Should I blead the brakes by pulling up the piston and clamping it? Problem maybe in the resrvoir?
I have replaced the seals in the master cylinder and the the wheel cylinders look good.

[Dikappa]

best to check and rebuild the reservoir, as the piston should always be up, also during normal use.  if not your brake will not feel correct.