My understanding and experience with hydraulic brake light switches used with Dot 5 is that they leaked not that they failed electrically. I haven't seen one fail electrically using Dot 5 but I have seen them fail through leaking. I wonder why Harley-Davidson would continue to use a hydraulic brake light switch with Dot 5 if there is a known electrical incompatibility. Sent from my Verizon, Samsung Galaxy smartphone -------- Original message -------- From: John Grady <jkg@xxxxxxxxxxxxxxxxx> Date: 4/24/23 7:50 AM (GMT-05:00) To: dplotkin <dplotkin@xxxxxxxxxxxxxxxxxxx> Cc: "D.C. Mason" <petergriffinforpresident@xxxxxxxxx>, 300 Club <chrysler-300-club-international@xxxxxxxxxxxxxxxx> Subject: Re: {Chrysler 300} Brake switch for silicone fluid I got into this after a few failures , I took one apart by cutting as i felt at the time it was inaccurate and anecdotal story that DOT 5 (which i use always ) causes switch failure . But here were failures , and i never had a hydraulic switch fail before —,ever . So inside the switch there was a white coating on the switch contacts . Further looking into it from EE perspective , there is some kind of chemical decomposition of the silicone oil when an intense enough arc happens in it . That probably means current level / heat when the contacts separate millionths of an inch as silicone itself is a very good insulator ( 40,000 v per .1” !) . The problem is not unlike points , and current is maybe 4 A, ok in oil or apparently glycol , but chemically the arc does something to silicone oil leaving an insulating residue on the contacts . So after seeing it myself , I admit to a 180 . Contacts in silicone oil are a bad idea no matter what you do , one might envision sliding self scraping contacts etc etc but the basic problem is real . I expected a bellows or something but contacts them selves were in the oil . These were stock switches . Unless a bellows is used moving contacts out if oil is in a Harley switch , it has to deal with the residue . ( like batteries discharging on cement floors — also true— another 180 ) . Best cure is microswitch on pedal box , V3 with a long arm is a good place to start to roll your own , — as it is a matter of when it fails ( number of operations ) not if . Being rear ended because of no brake lights and you don’t know that is not a happy day . Quick check watch ammeter when stepping you can see the jump . John
-- Sent from my iPhone On Apr 24, 2023, at 6:41 AM, dplotkin <dplotkin@xxxxxxxxxxxxxxxxxxx> wrote:
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