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PV, 120 (Amazon), 1800 General Forum for the Volvo PV, 120 and 1800 cars |
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Brake Light Shame....Views : 4289 Replies : 13Users Viewing This Thread : |
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Oct 20th, 2007, 01:03 | #11 |
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Last Online: Aug 11th, 2019 22:13
Join Date: Oct 2007
Location: Island of Kauai
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Thanks so much Andrew!
Looks like you even took a picture just to show me. The people on this forum are awesome....
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"Relax in the safety of your own delusions." - JR "Bob" Dobbs |
Oct 20th, 2007, 16:49 | #12 |
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Last Online: Today 16:27
Join Date: Jul 2007
Location: Connecticut, USA
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Hydraulic brake light switches vs. mechanical
Forum;
The pressure sensing hydraulic switches are just not reliable...the actual electrical contact area closes under slow-speed, low closing force...a perfect recipe for non-function from an engineering design standpoint... it's a poor situation...the pressure comes up very slowly during normal braking, and thus puts the switch diaphram through a linear (flexible) region which closes the contact quite slowly, typically not breaking through the carbonized surface (which occured when the contact was last carrying current and opened), when it should ideally snap closed, breaking through this non-conducting layer...add to that aging and relaxation of the diaphram, and most of the switches quit...some quite soon after installation...add to that the unavoidable delay factor of having to make pressure in the system in order to show brake lights, and all manufacturers including Volvo in about '67, changed over to mechanical switches. Regarding the "sludge" one poster found in the switch...I just can't believe this explanation...IMO, "sludge" is not likely what keeps the switch contacts from closing...in the first place, "sludge" would certainly transfer the pressure to the contact diaphram just as easily as clean fluid (I guess that means that just as a fluid is non-compressible, so is "sludge")...further, no "sludge" is capale of withstanding the high pressure which occurs in the system. I believe the failure mechanism is as described above. ...bottom line IMO is to just upgrade to a mechanical pedal position sensing switch, loose all of the disadvantages, and get all of the advantages: Reliably Brake Light operation the instant the pedal leaves its rest position. You don't even need to bleed the system!... Andrew; Please get back to me with your design if you would...I have another interested party for the RHD version and I could use the detailed design... Greetings from a foliage colorful New England! |
Oct 23rd, 2007, 20:38 | #13 |
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Last Online: May 17th, 2022 10:30
Join Date: Dec 2003
Location: northampton
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You might have already sorted this, but assuming your car is an Amazon, just get a new brake switch, the one thats on a bracket in front of the brake pedal. About £10 from Brookhouse and even an incompetent like me managed to fit this in 10 mins.
Brake lights were restored immediately. |
Dec 14th, 2007, 11:19 | #14 |
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Last Online: Today 16:27
Join Date: Jul 2007
Location: Connecticut, USA
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Failure of Hydraulic Brake Light Switches
Forum;
For those interested in my detailed explanation of the chronic failure of these switches, I have just completed a new tech article, which I invite you to read: http://www.sw-em.com/hydraulic%20bra...es%20notes.htm Cheers |
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