Hi all, My brake lights are not working. I know the bulbs work and the fuse is good so my thoughts have turned to the brake light switch. I looked under the van and locate the master cylinder. There is one electrical connection which looks like the switch but I also found another similar one that has just been cable tied out of the way and is not connected. Any ideas on what I'm looking at before I start to pull it apart
Fook knows what someone has done there... the switches run in parallel, so if one fails the other keeps working... What has happened is someone has replaced the MC, and it only has one switch outlet.... maybe they thought both switches needed to be in place for it to work...
So should the MC have two switch outlets then? Should I look at replacing this one?! I assume to test the brake lights I pull the connector off and touch the two wires together the lights should come on?
Just bridged the connector to the brake switch and the lights both work. Time for a new switch methinks
looks like someone has sorted out the spare switch connection with a rather over the top length of wire Leave that one for now. With the one connected unplug it and short it together like the other If your lights now on with the ignition switch on then it a duff switch If still not check you have 12v on one of the terminals
Noooooooo most replacement MCs have just the one outlet!! Originally you would've had 2 outlets for switches
^what they said. If the lights work when you short the switch socket contacts, likely the switch has packed up (did it ever work). Love that mains earth cable used for your brake light wiring
My replacement master cylinder had two outlets for switches but my wiring was for one. Not that it mattered - I changed to a switch operated by the brake pedal and fitted a bleed nipple to both switch outlets on the master cylinder. The hydraulic switches are too slow for my liking.
So, ive ignored the "extra" wiring and am focussing on the connector attached to the switch. I'm slightly confused now. I thought it was the switch but after I took the connector off and then put it back on the switch, the brake lights worked! I then took the connector off to clean it all up a bit, the re attached it, they stopped working! It seems to be a bit temperamental so I recon it's probably the switch. Lights worked absolutely fine when I attached both terminals together!
I'd take a close look at all that bodged wiring to check for breaks. Sounds like everything's working, apart from the bodgery.
“They should switch immediately. Summut up if not.” Hydraulic switches need pressure to operate so once the brakes are applied the brake lights illuminate but only when the brakes are already working. A switch on the pedal activates the brake lights before there is pressure in the hydraulic system and that fraction of a second may be the difference between being tail ended and a near miss. The speed of response is one of the reasons why hydraulic switches are no longer used.
I've mounted the switch on a simple bracket under the floor alongside the brake pedal; another small bracket is fixed on the side of the brake pedal to activate the switch. The existing wiring is shorted and new terminals attached. The switch is part number 13H3735 like this one: http://www.minispares.com/product/classic/13H3735.aspx The switch is adjusted so as the pedal moves and before the clearance in the linkage to the master cylinder is taken up the brake lights illuminate. Geoff
Really like the idea if this since mine is broken. Do you have any pictures of how it is currently installed? Matt
The hydraulic ones were used to indicate failures in the braking circuit(s) and drive the brake warning light if fitted.
All Bays have hydraulic switches for the brake lights, either a single switch or two interconnected switches if there is a brake failure warning circuit. This is a good description of the switches and how they work: http://www.huelsmann.us/bugman/brake_light_switch_tech.htm I agree it is quicker to replace a faulty hydraulic switch with a new one but then you are still left with the brake lights only coming on after the brakes are applied – that’s just how they work. Incidentally, it looks to me as if the OP may have originally had the wiring and sockets for the brake failure circuit but it has been converted to a single switch at some point.
