Brake Light Switch 1941 Cadillac

[Virgil Perkins]

Have a dumb question. Purchased a new brake light switch for my 1941 6019SF, found warning that the switch is not approved for use with silicone brake fluid. Why is this not compatible with silicone fluid? My current switch lasted 18 years and over 8,800 miles.(Have used silicone fluid from the get go.)Thanks in advance for educating a confused old man.V. Perkins, #19943

[harvey b]

Mine is the same way,its been in use for 15 years with the silicone fluid and its still works OK.I am planning to replace it with one that needs less pressure to work?,my lights dont come on until i press hard on the pedal,i want them to work even when i just touch the pedal.I have never heard of the silicone fluid not being compatible with them?. harveyb

[Bob Schuman]

I have had many brake light switch issues on my 41 over a period of 40 years. They would require increasing pedal pressure to operate the brake lights, eventually failing completely. A new switch from NAPA or other sources would restore normal operation, again gradually failing. This occurred with DOT 3 and later Silicone DOT 5 fluids. Seeing comments of the silicone fluid being the offender, I cut open several failed fluids from my car and others. Never did I find any evidence of the brake fluid reaching the contacts, but did find the contacts burned, causing poor to no electrical continuity. My opinion is that the switches available now are of poorer quality, resulting in short life. I have heard the Harley Davidson switches are much better, never tried one myself, so cannot comment on them.

Many years ago I designed a relay installation for the stoplights, using a horn relay. That reduces the current flow across the stoplight switch from about 5 amps to about 1/2 amp, and my switches lasted many years longer with that. I can provide the wiring diagram and details to anyone interested. The relay can be mounted in a location that only the most careful judge would ever notice it.

One switch I cut open was in service on a friend's 41 since at least 1972, and when it finally failed in about 1995 I cut it open and saw the obvious much stouter contacts and an assist spring to quickly open the circuit, both absent in the later switches.

[Virgil Perkins]

I have had many brake light switch issues on my 41 over a period of 40 years. They would require increasing pedal pressure to operate the brake lights, eventually failing completely. A new switch from NAPA or other sources would restore normal operation, again gradually failing. This occurred with DOT 3 and later Silicone DOT 5 fluids. Seeing comments of the silicone fluid being the offender, I cut open several failed fluids from my car and others. Never did I find any evidence of the brake fluid reaching the contacts, but did find the contacts burned, causing poor to no electrical continuity. My opinion is that the switches available now are of poorer quality, resulting in short life. I have heard the Harley Davidson switches are much better, never tried one myself, so cannot comment on them.

Many years ago I designed a relay installation for the stoplights, using a horn relay. That reduces the current flow across the stoplight switch from about 5 amps to about 1/2 amp, and my switches lasted many years longer with that. I can provide the wiring diagram and details to anyone interested. The relay can be mounted in a location that only the most careful judge would ever notice it.

One switch I cut open was in service on a friend's 41 since at least 1972, and when it finally failed in about 1995 I cut it open and saw the obvious much stouter contacts and an assist spring to quickly open the circuit, both absent in the later switches.

Thank you Bob, good to hear from you and I appreciate the info. If the new switch lasts even half as long as my current hummer, I will be happy! Do have more switches coming just in case.

[Virgil Perkins]

Mine is the same way,its been in use for 15 years with the silicone fluid and its still works OK.I am planning to replace it with one that needs less pressure to work?,my lights dont come on until i press hard on the pedal,i want them to work even when i just touch the pedal.I have never heard of the silicone fluid not being compatible with them?. harveyb

Thanks for info Harvey.

[Virgil Perkins]

Thank you Bob, good to hear from you and I appreciate the info. If the new switch lasts even half as long as my current hummer, I will be happy! Do have more switches coming just in case.

Me again Bob, I would like to see your horn relay modification. Thanks, VP