39 Dlx: New brake light switch not working

M

Mike/NY

Member
Brake light switch did not work due to sitting and silicon brake fluid. Swapped in a new switch, still nothing? I only took the old one off and while fluid was dripping out quickly screwed a new one. Worked before. Any suggestions?
 
Mike, This is a simple circuit to test. As you'd stated "it worked before" then I will apprehensively assume the wiring is fine. That being (hopefully the case) you'll need to test the switch.
One side of the switch (terminal) should light up your test lamp all the time. When a helper depresses the brake pedal, the other terminal should light up.
If the "second" terminal doesn't light up with pedal pressure the switch is defective.

If the "first" terminal is not lit up, then there is an issue in the wiring before the switch.
 
Like Mike suggested, first test the switch. In today's world "NEW does NOT always = Good" for just about any parts that you buy.
A more fundamental problem is the silicone brake fluid. The original switch most likely failed due to the silicone brake fluid seeping by the internal seal in the switch and preventing the contacts from well, making contact. I would suggest you flush the system completely and install DOT 4 non silicone fluid. A new (good) pressure switch will most likely fail at some point too with the silicone.
Many using silicone fluid have replaced the pressure switch with either a Harley pressure switch made for silicone fluid, or a mechanical lever switch like a 55-59 GM pickup uses.
 
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The last time I bought a switch that was compatible with silicon it came from Ron Francis Wire Works, (800) 292-1940. They also have some brite (their spelling) bulbs but unless they added something they are 12 volts.

Charlie Stephens
 
I always fill the new switch port with brake fluid before installing. I have a Harley switch and have been using silicone brake fluid for at least eight years.
 
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