Hi All, Looking for some advice. I have recently noticed that my brake lights only come on when substantial pressure is applied to the brake pedal. I have replaced the brake light switch on the master cylinder and bleed the brakes. This made no difference. The servo, in fact the whole braking system, is brand new. I understand that the switch is a hydraulic pressure activated switch, and so some pressure has to be applied to the brake pedal before the lights will come on, but surely not as much as having to put your foot half way to the floor!? The brakes work really well. Pedal feel is not spongy at all. Anyone got any ideas?
switch would seem the logical problem. Have you tried to bridge the wires that connect to the switch, and get some one to confirm they come on brightly....if they do maybe you have got a bad switch even though it is new Could be something wiring related, such as a bad connection. You could try cleaning the earth on the rear lights and the spade connectors that connect to the break switch as they get pretty dirty ......maybe air in the break system so you need to push harder before the pressure operates the switch maybee
Thanks chaps. I'll check the connections and the rear brake adjustment over the weekend. I did read elsewhere that unscrewing the brake switch slightly, then getting someone to press the brake pedal so that fluid is forced out, then screwing the switch back up, helped them to expel an air bubble that was causing the same problem. This cured it for them. Wasn't a camper though.
Worth trying what @Diddymen suggested as an easy first step: just short the terminals on the brake light switch.
Make sure that you free off the handbrake cables before/if you adjust the rear brakes, it is a faff but really will pay off.
What if you have a break in the core of the wire from the master cylinder to the brake lights so that what you are doing is bending the master cylinder back with with the pressure from the pedal/servo so it makes connection. Try pulling hard on the wire teminating spade connector( after disconnecting it from the switch ) that goes onto the switch If all the wire cores are there it should stay together. If cores are broken the insulation will stretch and snap. Then that is where the problem is. (Now , anyway) Or pull it off more carefully and look for continuity to earth from the wire througgh the brake lights or short out the switch and see if the lights come on.
I've had 3 switches in 3 years, don't know why they keep breaking. I guess it's the usual aftermarket crap parts. Next time the switch goes I'm going to convert the electrics to work off a switch which attaches to the pedal. I think I saw someone on here do this too, will be easy to do.
I did it several years ago. I used a switch from a mini, part number 13H3735, and made suitable brackets under the floor to hold the switch and on the pedal to operate the switch. I removed the switches from the master cylinder and replaced them with bleed nipples.
Hello chaps. Thanks for the advice so far. I took a look underneath today, and noticed that the wires to the switch had bodged up extensions (extra length of wire with end twisted around the end of the main wire to form a join then taped over). I removed these and fitted new connectors. I then fitted a bridging wire between them, turned the ignition on, and the brake lights came on nice and bright. So, I'm thinking the electrical part of the system is ok. I then removed the bridging wire and connected up the wires to the switch and got the wife to stand at the back of the bus whilst I pressed the brake pedal. Still only coming on when the pedal is down about a third of the way. Bugger! A couple of other points, the brake pedal feel is really solid, and only goes down about a third of the way (sorry I said half way in my first post). Also, I have noticed there is three connectors on the switch, but only two wires! Does this matter? Do the wires go on specific connectors? Also, there is an older looking switch on the back of the master cylinder, also with three connectors, but no wires attached to it. Strange! Any other thoughts? Cheers
The two 3-pin switch arrangement was for driving a brake light warning switch on the dash (have you got a red "B" light on the instrument panel?) Someone's obviously "improved" the wiring over the years. You could try replacing the 3-pinner for a two pin job.
Have you got a brake warning light on your dashboard.. and if so does it work , should go on if pressure in the system fails . Mine only comes on to warn me that the handbrake is on. Can't honestly remember now how I did it but will try retrace the wizardry and report back if you are interested.
@snotty beat me to it. But if I remember rightly you can get it to warn you that the handbrake is dragging by using a simple Golf brake switch.
Ah, ok. I wondered what the extra switch was for. No, there isn't a "B" light on the instrument cluster. There is a round black blanking plug nearest the red heater control leavers though. Is that where this "B" light would be? Or would it be with the other lights that are integral to the petrol gauge? Does it matter whether you have the three pin or two switch? Do they work differently? I see that JK stock both for the late Bay. I can't see any other wires to connect up.
The lights work by the pressure in the system, if your pedal goes a third of the way down before resistance is felt that will be when the light comes on !! Have you tried a new switch ?
Two pins is fine. It'll just operate the brake lights. The double 3-pin job was to indicate whether there was a pressure failure in one or other of the brake circuits. US-spec busses commonly have them.
