Stop/brake light switch failure

Joined
Feb 24, 2016
Messages
8
Location
Charlotte, NC
I went to swap brake light switches yesterday as the original flickers when driving and comes on at night. Replaced with new napa switch, i let the switch dangle to make sure it worked before bolting it up. Bolted it back up and the lights cut out and would not work with the original switch or the new switch. Checked fuses and none blown. Voltage tested the car side of wiring and getting 12.5v, tested new switch as well as old switch for continuity and both are positive for continuity. At a loss at this point, anyone got ideas on whats going on?
 
Joined
Nov 3, 2014
Messages
191
Location
Kansas City
Don’t know if this will help, but I had this happen awhile back. It ended up being an exposed wire on the trailer pigtail that hit some metal and shorted out. I do believe in my case, however, I found a blown fuse.
 
Joined
Feb 24, 2016
Messages
8
Location
Charlotte, NC
What year Cruiser? Also, when you say you tested the car side wiring, where exactly did you probe?
What year Cruiser? Also, when you say you tested the car side wiring, where exactly did you probe?
What year Cruiser? Also, when you say you tested the car side wiring, where exactly did you probe?
93 Cruiser. Testing across terminals 1 and 2 on the plug side yields 12v, which to me indicates power to the switch and no blown fuse. Also replaced fuse with no luck.

F97FA018-3127-4D34-9EF9-6C02BAD8D883.jpeg
 
Joined
Mar 11, 2022
Messages
104
Location
California
I would plug the switch back in. Backprobe and make sure you have 12v at pin 2 and not at pin 1. Then depress the switch and make sure you have 12v at both pins 1 and 2. Don't use the factory wiring for ground on the meter. Use a good grounded bolt or something in the vicinity. If have voltage at both pins, the switch is working and sending 12v downstream. Then check the Green/White wire at the brake light bulbs while depressing the switch. If you don't have voltage, you have a break in the wire (check around under the dash since you moved those wires when replacing the switch). If you do have voltage there, then check your bulbs, bulb connections, and grounds. It's a pretty simple circuit. The power goes through the fuse, to the switch, through the switch, to the bulb, through the bulb, and to ground. Follow the voltage and see where you lose it.
 
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Joined
Feb 24, 2016
Messages
8
Location
Charlotte, NC
I would plug the switch back in. Make sure you have 12v at pin 2 and not at pin 1. Then depress the switch and make sure you have 12v at both pins 1 and 2. If you do, the switch is working and sending 12v downstream. Then check the Green/White wire at the brake light bulbs while depressing the switch. If you don't have voltage, you have a break in the wire (check around under the dash since you moved those wires when replacing the switch). If you do have voltage there, then check your bulbs, bulb connections, and grounds. It's a pretty simple circuit. The power goes through the fuse, to the switch, through the switch, to the bulb, through the bulb, and to ground. Follow the voltage and see where you lose it.
Thanks for the direction. Will check that out to make sure switch is functioning properly and no downstream breaks.

Also can’t shift out of park and had to manually override shifter to get back to the house. Know that switch also sends signal to shifter as well. Providing this for additional info.

Thanks!
 
Joined
Mar 11, 2022
Messages
104
Location
California
Thanks for the direction. Will check that out to make sure switch is functioning properly and no downstream breaks.

Also can’t shift out of park and had to manually override shifter to get back to the house. Know that switch also sends signal to shifter as well. Providing this for additional info.

Thanks!
Yeah that sounds like a bad switch or a break in the wire. Pins 1 and 2 control brake lights and shift interlock. Pins 3 and 4 are for cruise control.
 
Joined
Feb 24, 2016
Messages
8
Location
Charlotte, NC
Tested both sides of switch. 12v good, so switch good. Tested green/white in back of truck with no voltage. Found broken wire under dash from previous crappy audio store install of a remote start. All good and working now. Thanks @Racefiend for talking us through what now seems like a simple electrical process.

Hard to see the forest through the trees when you’re in the middle of a non-working rig. Preesh!
 
Joined
Mar 11, 2022
Messages
104
Location
California
Tested both sides of switch. 12v good, so switch good. Tested green/white in back of truck with no voltage. Found broken wire under dash from previous crappy audio store install of a remote start. All good and working now. Thanks @Racefiend for talking us through what now seems like a simple electrical process.

Hard to see the forest through the trees when you’re in the middle of a non-working rig. Preesh!
You're welcome! Glad you were able to get it figured out. I'm going to guess the audio place used vampire taps. Those things are garbage.
 
Joined
Feb 24, 2016
Messages
8
Location
Charlotte, NC
Surprised to not find any taps, it was a wire splice in and wrap up with no solder. Disappointing, just more reassurance to do all my own work.
 

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