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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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 Posted: Mon Mar 27, 2023 12:31 pm Post subject: Brake warning light |
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Hi all, long time, no write.
My brake lights went out on me. I replaced the switch that attaches to the master cylindar. Brake lights now work OK. Car sat a few days. Took it out today, and the brake warning light on the dash is on all the time, UNLESS i step on the brake pedal. Then it goes off. I checked the fluid level, it's fine. What gives?
thanks,
Lori & The Baroness, 1971 SB automatic carbed |
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Bobnotch
Samba Member
Joined: July 06, 2003
Posts: 22410
Location: Kimball, Mi
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| Posted: Mon Mar 27, 2023 1:56 pm Post subject: Re: Brake warning light |
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Lori, just a heads up, but there's been an on going issue of the switches being made wrong. I think Sean found that a Harley Davidson switch uses metric fitting and is wired correctly inside to be used as a replacement. Keep in mind that it's a 2 pole switch, versus the 3 pole switch you want. Unfortunately this has been an on going problem for the last 5+ years. I don't know why suddenly yours decided to quit. Usually when the warning light comes on, you've already felt a problem with the brakes. At least that's how Jim Adney feels about it (me too). You could try and see if he has a good 3 pole switch.
I hope this helps.
_________________
Bob 65 Notch S with Sunroof
71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120
| Tram wrote: |
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| Tram wrote: |
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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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| Posted: Mon Mar 27, 2023 5:03 pm Post subject: Re: Brake warning light |
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| Bobnotch wrote: |
You could try and see if he has a good 3 pole switch.
I hope this helps. |
Hey,
I'm not sure what you mean by "pole"? Do you mean the prongs that come out of the switch? It had 3. The switch I replaced was the onw that turns the brake lightss on when you step on the brake, not the other one. I'm not even sure what that does.
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Bobnotch
Samba Member
Joined: July 06, 2003
Posts: 22410
Location: Kimball, Mi
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| Posted: Tue Mar 28, 2023 2:20 pm Post subject: Re: Brake warning light |
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It looks like you have 2 three terminal switches. It might be worth checking them both and see if one went bad. If I remember right the 2 outer terminals are for the brake lights, while the middle one is for the warning light. Both sides get power from the black wire with power (key) on. On my own car, I swapped to using the 2 terminal switches, as I don't really need the warning light as my foot will feel a problem if I'm having one.
I hope this helps.
_________________
Bob 65 Notch S with Sunroof
71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120
| Tram wrote: |
| "Friends are God's way of apologizing for relatives." |
| Tram wrote: |
| People keep confusing "restored" and "restroyed". |
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5994
Location: Brooklyn
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| Posted: Tue Mar 28, 2023 3:25 pm Post subject: Re: Brake warning light |
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| Fiesta Cranberry wrote: |
The switch I replaced was the onw that turns the brake lightss on when you step on the brake, not the other one. I'm not even sure what that does.
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This may be part of the problem, in that you misunderstand how it works.
*Both* those switches turn on the brake lights. Either one will do it by itself, but there are two hydraulic circuits in that master cylinder and each circuit has its own pressure switch to activate the brake lights. That way, if one hydraulic circuit fails, you still have brake lights.
So most likely the other switch is bad too. Because the brake lights don't fail til both of the switches die. Because when the first switch dies, the brake lights still work so you don't know it's dead. Then when the second switch finally dies you no longer have brake lights.
So I would replace the switch you didn't replace yet - you can test it first, but if it worked your brake lights wouldn't have died. 
Any weirdness after that may be a result of miswiring the switches. One of your switches still has the original connector plug to keep you from miswiring it - the other does not. Hint hint.
_________________
1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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| Posted: Tue Mar 28, 2023 4:27 pm Post subject: Re: Brake warning light |
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| sjbartnik wrote: |
So most likely the other switch is bad too. Because the brake lights don't fail til both of the switches die. Because when the first switch dies, the brake lights still work so you don't know it's dead. Then when the second switch finally dies you no longer have brake lights.
Any weirdness after that may be a result of miswiring the switches. One of your switches still has the original connector plug to keep you from miswiring it - the other does not. Hint hint. |
OH! OK, that makes sense---I DO have brake lights, but my dash light is on UNLESS i step on the brake pedal. How do I know which wire goes where? Will rearranging the wires make the dash light go out?
Are both switches the same? I'll have to order a new one for the top, and I need to know what to order.
Thanks! |
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5994
Location: Brooklyn
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| Posted: Tue Mar 28, 2023 4:41 pm Post subject: Re: Brake warning light |
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Yes both switches are the same.
The wiring diagram provides the key as to how it should be wired - usually the two terminals on the switch that are parallel to each other are for the main brake lights (the black or black/red wires) and the one terminal that's in the center at a 90 degree angle to the others is the one for the warning light on the dash and gets the red wire.
The way the dash warning light works is that if there is good hydraulic pressure in both brake circuits, both switches close when you apply the brakes and the brake lights in the rear come on and the warning light on the dash stays off.
If you have a situation where one hydraulic circuit does not have sufficient pressure, then you will have a deal where one switch closes and one does not when you apply the brakes. The difference is supposed to cause the brake light on the dash to light up and warn you that you have a failure - though usually the pedal going down to the floor is sufficient warning!
Yours is kind of acting in the reverse way which makes me think of miswiring, so check your work and I still think you need to replace the other switch.
_________________
1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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| Posted: Tue Mar 28, 2023 5:46 pm Post subject: Re: Brake warning light |
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| sjbartnik wrote: |
Yes both switches are the same.
If you have a situation where one hydraulic circuit does not have sufficient pressure, then you will have a deal where one switch closes and one does not when you apply the brakes. The difference is supposed to cause the brake light on the dash to light up and warn you that you have a failure - though usually the pedal going down to the floor is sufficient warning!
Yours is kind of acting in the reverse way which makes me think of miswiring, so check your work and I still think you need to replace the other switch. |
Thank you so much! Is there any way to know if both switches are working besides changing them out? Brakes seem to be working and feel OK. |
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sjbartnik
Samba Member
Joined: September 01, 2011
Posts: 5994
Location: Brooklyn
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| Posted: Tue Mar 28, 2023 7:56 pm Post subject: Re: Brake warning light |
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Yes you can test the switches, don't even need the key on, but you do need a helper.
Put your multimeter across the two parallel terminals and set it to measure resistance. First test with the brake pedal not applied, you should see something like infinite resistance across the two terminals. Then have your helper push the brake pedal down firmly, you should see the resistance drop to near zero when the switch closes. If it doesn't, either the switch is bad or there is too much air in the circuit to generate enough pressure to close the switch. But if the latter is the case that can usually be felt with soft pedal and poor braking - typical symptoms of air in the lines.
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1965 Volkswagen 1500 Variant S
2000 Kawasaki W650 |
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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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| Posted: Wed Mar 29, 2023 10:34 am Post subject: Re: Brake warning light |
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| sjbartnik wrote: |
Yes you can test the switches, don't even need the key on, but you do need a helper.
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Thank you again! I'm waiting for it to stop raining, so I can go out and look under the car at the wiring. |
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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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| Posted: Fri Mar 31, 2023 3:31 pm Post subject: Re: Brake warning light |
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| sjbartnik wrote: |
The wiring diagram provides the key as to how it should be wired - usually the two terminals on the switch that are parallel to each other are for the main brake lights (the black or black/red wires) and the one terminal that's in the center at a 90 degree angle to the others is the one for the warning light on the dash and gets the red wire.
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OK, I was finally able to get under the car today. First off, I bon't have a black/red wire. I have black, red, and red/grey. I switched the 2 side wires, and the brake lights were on UNTIL I stepped on the pedal. THEN they went off, LOL. I also tried switching the middle with each side. Then nothing worked. So, I put it back the way it was. So now I have brake lights when I step on the pedal. But the dash light is on all the time until i use the brake pedal.
I ordered a second switch for the other side. |
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Bobnotch
Samba Member
Joined: July 06, 2003
Posts: 22410
Location: Kimball, Mi
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| Posted: Sat Apr 01, 2023 9:21 am Post subject: Re: Brake warning light |
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| Fiesta Cranberry wrote: |
| sjbartnik wrote: |
The wiring diagram provides the key as to how it should be wired - usually the two terminals on the switch that are parallel to each other are for the main brake lights (the black or black/red wires) and the one terminal that's in the center at a 90 degree angle to the others is the one for the warning light on the dash and gets the red wire.
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OK, I was finally able to get under the car today. First off, I bon't have a black/red wire. I have black, red, and red/grey. I switched the 2 side wires, and the brake lights were on UNTIL I stepped on the pedal. THEN they went off, LOL. I also tried switching the middle with each side. Then nothing worked. So, I put it back the way it was. So now I have brake lights when I step on the pedal. But the dash light is on all the time until i use the brake pedal.
I ordered a second switch for the other side. |
OK, it seems that you were working with the front switch, and verified it's working (lighting the rear brake lights). I'd unplug the rear switch, then see if the dash warning light goes out. If it does, then you've verified the rear switch has gone bad.
_________________
Bob 65 Notch S with Sunroof
71 Notch ...aka Krunchy; build pics here;
http://www.thesamba.com/vw/forum/viewtopic.php?t=249390 -been busy working
64 T-34 Ghia...aka Wolfie, under construction... http://www.thesamba.com/vw/forum/viewtopic.php?t=412120
| Tram wrote: |
| "Friends are God's way of apologizing for relatives." |
| Tram wrote: |
| People keep confusing "restored" and "restroyed". |
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Fiesta Cranberry
Samba Member
Joined: August 07, 2007
Posts: 13
Location: San Francisco, CA
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| Posted: Sat Apr 01, 2023 12:11 pm Post subject: Re: Brake warning light |
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| Quote: |
OK, it seems that you were working with the front switch, and verified it's working (lighting the rear brake lights). I'd unplug the rear switch, then see if the dash warning light goes out. If it does, then you've verified the rear switch has gone bad. |
OK, thanks! I tried to unplug the cap thingy on the rear switch, and I didn't have enough strength in my fingers. I can try again using rubber gloves. That might give me a better grip. I just picked up another switch today. |
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