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914World.com _ 914World Garage _ Early 914 brake light switch
Posted by: isdyl Sep 11 2018, 02:08 AM
Hi, I'm have a difficult time obtaining a brake two pole brake light switch for my 914 here in the uk. It is a Bosch 0343102008 as seen in the photo with the mechanical plunger. It screws into the side of the master cylinder. Bosch have no stock and I have just found one available at a Porsche dealer for £80 which I am reluctant to spend. Mine is leaking and I have tried epoxy to repair it but no luck. I was thinking that there must be pressure in the plunger area when in operation as it leaks and forced past the epoxy, so could I use another two pole pressure switch provided it has the correct thread? (12x1mm I think). Has anyone else replaced their plunger type switch with an alternative? The later cars use a single pole 0343102010 which works in a similar way but I think grounds through the switch body when the plunger is pressed rather than connecting the two poles.
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Posted by: Tbrown4x4 Sep 11 2018, 02:26 AM
I just replaced my M/Cylinder with a 19mm 914 Rubber one. It came with a single pole switch and it works fine. Just check the wiring diagram for which wire needs to be attached to it.
Posted by: isdyl Sep 11 2018, 02:54 AM
Oh thats interesting thanks - maybe one of the wires is just an earth. I'll study the wiring diagram.
Posted by: isdyl Sep 11 2018, 03:09 AM
Oh thats interesting thanks - maybe one of the wires is just an earth. I'll study the wiring diagram.
No, it looks like one wire is a live supply from the fuse board and the other goes to the tail lamps. I think it needs to be a two connector switch.
Posted by: Tbrown4x4 Sep 11 2018, 04:28 AM
I'd check for you, but I'm at work.
What year are we looking at? I have a '73.
OK. Just remembered I have a wiring diagram in my car. I'm showing two inputs that turn on the brake warning light. The Parking brake contact and the "brake warning light switch", which should be the one on the brake master. The is a brown wire and a white with a brown stripes. I hooked up the white/brown wire to the switch and left the brown ground wire taped off.
Posted by: Tbrown4x4 Sep 11 2018, 04:53 AM
I don't think brake fluid should be coming out of the switch at all. There are seals on the "pistons" that actuate the switch when one circuit loses pressure. Maybe you are due for a new or rebuilt M/Cyl.
Posted by: isdyl Sep 11 2018, 06:01 AM
Hi, Mine is an early '73 and I don't think it had a brake warning except for the switch under the parking brake to indicate the parking brake is on. The wiring diagram I was looking at is this one:
http://nicoh.me/porsche-914-wiring-diagram.html/1973-porsche-914-wiring-diagram-and
Item 35 is the switch on the master cylinder and I think it just mechanically operates the tail stop lights. It has 12v supply one side (shared by something else number 90) and supplies 12v to the tail lamps when pressed. I could be wrong?
Posted by: Tbrown4x4 Sep 11 2018, 06:58 AM
I think 35 is the switch on the brake pedal. What color wires are going to your switch?
Posted by: ClayPerrine Sep 11 2018, 11:36 AM
Hi, I'm have a difficult time obtaining a brake two pole brake light switch for my 914 here in the uk. It is a Bosch 0343102008 as seen in the photo with the mechanical plunger. It screws into the side of the master cylinder. Bosch have no stock and I have just found one available at a Porsche dealer for £80 which I am reluctant to spend. Mine is leaking and I have tried epoxy to repair it but no luck. I was thinking that there must be pressure in the plunger area when in operation as it leaks and forced past the epoxy, so could I use another two pole pressure switch provided it has the correct thread? (12x1mm I think). Has anyone else replaced their plunger type switch with an alternative? The later cars use a single pole 0343102010 which works in a similar way but I think grounds through the switch body when the plunger is pressed rather than connecting the two poles.
Just checking to make sure you are aware... the actual switch that lights the brake lights is located inside the passenger compartment on the pedal box. The switch you picture is for the brake failure warning light in the left hand gauge.
The two pole switch has been superseded by the single pole switch. Just buy the single pole, and leave the brown (earth) wire disconnected.
Posted by: isdyl Sep 11 2018, 11:51 AM
Ah yes! Brilliant - thanks - this forum is excellent. I have just dug around under the peddles and seen the other switch. You have saved me a load of bother trying to get that 2 pole switch.
I actually wrote to Bosch last week saying I couldn't locate a 2 pole version and could I use a 0343102010. They couldn't have been less helpful - I'm actually quite annoyed by their 'couldn't care less' replies!
Posted by: ClayPerrine Sep 11 2018, 02:55 PM
Ah yes! Brilliant - thanks - this forum is excellent. I have just dug around under the peddles and seen the other switch. You have saved me a load of bother trying to get that 2 pole switch.
I actually wrote to Bosch last week saying I couldn't locate a 2 pole version and could I use a 0343102010. They couldn't have been less helpful - I'm actually quite annoyed by their 'couldn't care less' replies!
If you have to replace the switch, make sure the little arm is behind the big washer on the brake rod. The switch is held open by the brake rod, and closes with a spring when the brake is depressed.
Also be careful of wire routing to the brake light switch. You can accidentally get it in the way of the accelerator bell crank. That will pull the wires off the switch. And the MOT won't like that.
Posted by: isdyl Sep 12 2018, 01:23 PM
Ok so the other switch isn't available either! Should I just blank it off with a plug? What does this switch actually do please? I think it's some kind of warning switch, and I spoke to someone today who thought it sent a message to the injection system not to provide fuel if the brake is pressed (?). I'm not sure its needed.
Posted by: bbrock Sep 12 2018, 02:33 PM
You mean this one? https://www.amazon.com/Brake-Switch-PORSCHE-91161341100-91161341101/dp/B07932Y7H6
or this one?
https://www.ebay.com/itm/Brake-Light-Switch-0343102010-Bosch-61311350350-01171676-1171676-91461311600-New/232518763059?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D41376%26meid%3Df4d0715926e94fca918e205c88134ca8%26pid%3D100623%26rk%3D2%26rkt%3D3%26sd%3D292153740400&_trksid=p2047675.c100623.m-1
Search on part numbers ( 91161341100 and 91461311600). Lots of options.
Posted by: isdyl Sep 12 2018, 02:39 PM
Yes exactly those ones. I’ve ordered 3 so far but each time the seller has come back to me saying sorry they aren’t available. These guys just wait till they get an order and order it from Bosch. Bosch have none.
Posted by: bbrock Sep 12 2018, 02:46 PM
Yes exactly those ones. I’ve ordered 3 so far but each time the seller has come back to me saying sorry they aren’t available. These guys just wait till they get an order and order it from Bosch. Bosch have none.
Oh, that sucks. I'd contact 914rubber about the warning switch on the master cylinder. They include them on the master cylinders they make so are getting them from somewhere. It looks like they are both still available from Porsche but not cheap. Either could save your life though so I wouldn't delete them.
Posted by: 914Sixer Sep 12 2018, 08:25 PM
I have one. Contact me. It is also a stock VW Bug part. 113.945.515E
Posted by: isdyl Sep 13 2018, 10:39 AM
I have one. Contact me. It is also a stock VW Bug part. 113.945.515E
That would be great, but I'm unfortunately in the UK. I called VW but unfortunately they stoped using them in the early '80's and they have been deleted of their system. Maybe its a UK problem - I may have to import one somehow.
Posted by: 914Sixer Sep 13 2018, 03:34 PM
Sent you a PM
Posted by: 914Sixer Sep 14 2018, 12:44 PM
I only have a clean used one. Yours for free now. Will get shipping later on today.
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Posted by: isdyl Sep 14 2018, 02:49 PM
Wow thats fantastic - thank you so much! I must give you something for it though - and the shipping.
Regards, Dylan
Posted by: isdyl Sep 16 2018, 01:50 AM
Brilliant - 914Sixer has sent me one - thank you very much!
Here is the car by the way. Still a few jobs to do but not too far off being on the road.
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Posted by: isdyl Sep 23 2018, 01:39 PM
Its arrived! Thank you very much again.
Dylan
Posted by: isdyl Apr 11 2019, 03:07 AM
Hi, sorry to resurrect my old thread, but I'm still having a few issues with brake pressure. I've done quite a lot of searching around but before I waste any more time removing wheels again I thought I'd describe my symptoms and see if I'm barking up the wrong tree!
I replaced the brake pressure switch kindly sent to me by 914Sixer and have bled the brakes a couple of times.When I'm driving or stationary with the engine on I get a clicking/ticking from the flasher relay (but no warning light flashing). If I press the brake pedal the clicking/ticking stops for about 5 seconds and then starts again. It I apply the parking brake when stationary the light on the dash flashes in time with the ticking (as it should). Indicators all work as they should. In some places I have read that the switch needs resetting, but I don't think this is that type as there is no reset button. I wonder if I just need to keep bleeding the brakes - maybe I have air trapped somewhere? I have read that air can get trapped in the brake proportioning valve - could this cause this problem please?
Thanks, Dylan
Posted by: 914Sixer Apr 11 2019, 06:28 AM
Check your hand brake switch. Make sure it is pushing it all the way down. Easy to take out the screw and check for movement or corrosion. It is a single pole VW door switch. There is NO reset on MC switch.
Posted by: Spoke Apr 11 2019, 07:42 AM
I replaced the brake pressure switch kindly sent to me by 914Sixer and have bled the brakes a couple of times.When I'm driving or stationary with the engine on I get a clicking/ticking from the flasher relay (but no warning light flashing). If I press the brake pedal the clicking/ticking stops for about 5 seconds and then starts again. It I apply the parking brake when stationary the light on the dash flashes in time with the ticking (as it should). Indicators all work as they should. In some places I have read that the switch needs resetting, but I don't think this is that type as there is no reset button. I wonder if I just need to keep bleeding the brakes - maybe I have air trapped somewhere? I have read that air can get trapped in the brake proportioning valve - could this cause this problem please?
Thanks, Dylan
This phantom clicking of the flasher relay is unfortunately not that rare. I'm working with a 911 owner with the same problem. The issue seems that if there is some electrical leakage path from pin 49a to ground the flasher will flash (click) without any lights lighting up. If the leakage path is through the brake warning light, it might be so that there is enough current to trigger the flasher but not actually light up the bulb.
You can check this by either popping out the dash gauge and removing the brake warning bulb. If the clicking stops then it has to do with the wiring of the brake warning light.
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Posted by: isdyl Apr 11 2019, 03:03 PM
Thank you - I'll have a good look at that. D
Posted by: isdyl Jul 10 2019, 07:43 AM
Hi - sorry its taken me a long time to follow this up! I removed the wires to the warning lamp and yes the ticking has stopped - hooray! I'll have to start hunting around for the short/leakage now. Thanks - I'll start near the parking brake area as that switch is a bit dodgy. D
I replaced the brake pressure switch kindly sent to me by 914Sixer and have bled the brakes a couple of times.When I'm driving or stationary with the engine on I get a clicking/ticking from the flasher relay (but no warning light flashing). If I press the brake pedal the clicking/ticking stops for about 5 seconds and then starts again. It I apply the parking brake when stationary the light on the dash flashes in time with the ticking (as it should). Indicators all work as they should. In some places I have read that the switch needs resetting, but I don't think this is that type as there is no reset button. I wonder if I just need to keep bleeding the brakes - maybe I have air trapped somewhere? I have read that air can get trapped in the brake proportioning valve - could this cause this problem please?
Thanks, Dylan
This phantom clicking of the flasher relay is unfortunately not that rare. I'm working with a 911 owner with the same problem. The issue seems that if there is some electrical leakage path from pin 49a to ground the flasher will flash (click) without any lights lighting up. If the leakage path is through the brake warning light, it might be so that there is enough current to trigger the flasher but not actually light up the bulb.
You can check this by either popping out the dash gauge and removing the brake warning bulb. If the clicking stops then it has to do with the wiring of the brake warning light.
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