I remember staring at a mess of wires under my old pickup, a fresh brake light switch in hand. The left one had finally given up the ghost, leaving me with a single, sad red glow when I hit the pedal. My first thought, naturally, was: can I run two brake light switches in parallel? Why bother with one when two could offer a backup, right? It seemed like a smart, simple way to avoid getting rear-ended because of a cheap, failure-prone part. But like a lot of ‘simple’ automotive fixes, it’s got more quirks than a vintage Triumph.
Wiring up a second switch in parallel sounds like a foolproof plan to make sure your brake lights always work. If one fails, the other takes over. What could go wrong?
Well, quite a bit if you don’t understand how the circuit actually behaves. It’s not just about connecting wires; it’s about understanding the flow of electricity and the potential pitfalls that come with seemingly doubling up on a simple component.
Why You’re Even Asking: The Single Switch Blues
Look, nobody buys a new brake light switch because they’re bored. Usually, it’s because the old one decided to retire early, leaving you with no brake lights, or worse, brake lights that stay on all the time. I’ve been there. My ’87 Corolla’s switch went kaput right before a long road trip. It started with them staying on constantly – a surefire way to annoy everyone behind you and potentially drain your battery if you weren’t careful. Then, after a few days of fiddling, they just stopped working altogether. That’s a terrifying feeling, realizing your car is suddenly invisible to other drivers when you’re slowing down.
The brake light switch is basically a simple on/off mechanism. When you press the brake pedal, it closes a circuit, sending power to the brake light bulbs. When you release the pedal, it opens the circuit, and the lights go off. It’s a tiny, often plastic thing, usually mounted near the brake pedal arm.
They take a beating, being pressed hundreds of times a day, often with a bit more force than necessary from an impatient foot. They are also exposed to dust, dirt, and general road gunk that finds its way into the cabin.
Considering all that, it’s no wonder they fail. I’ve replaced them on everything from a Honda Civic to a Ford F-250, and the story is always the same: they’re a common failure point.
The common advice is always: replace it with a new one. And yeah, usually that’s the correct fix. But the idea of redundancy, of having a backup, is super appealing. Especially when you consider the cost. A decent brake light switch might set you back anywhere from $15 to $50, depending on the car. It’s not bank-breaking, but when you’re trying to keep an old car on the road without spending a fortune, every little bit counts. So, the question, ‘can i rin two brake light switches in parralel,’ starts to look like a very practical, cost-saving, and safety-enhancing solution.
The standard brake light circuit is incredibly basic. Power comes from the battery, through a fuse, then to the switch.
When the switch is activated (pedal pressed), it completes the circuit, sending power out to the brake light bulbs. There’s usually a single wire going to the switch and another wire going from the switch to the lights. It’s elegant in its simplicity, but that simplicity is also its weakness. A single point of failure means when that switch goes, your brake lights go with it.
This is where the idea of parallel switches starts to sound like genius. Wouldn’t it be safer if, when the primary switch fails, a secondary one could still activate the lights? It’s a question many DIY mechanics ponder.
How Parallel Wiring Actually Works (and Why It’s Tricky)
So, you’ve got the idea: wire two switches so that if one fails, the other still works. This is where the concept of parallel wiring comes into play. In a parallel circuit, components are connected side-by-side, offering multiple paths for electricity to flow. For brake light switches, this would mean connecting the ‘power in’ terminal of both switches together, and then connecting the ‘power out’ terminal of both switches together. The combined ‘power out’ then goes to your brake lights.
Let’s visualize this. Imagine a river (electricity) flowing to a junction with two gates (switches). If you want the water to reach the other side as long as at least one gate is open, you wire them in parallel. If the first gate is closed, the water can still go through the second gate. If the second gate is closed, the water can go through the first. If both are open, even more water flows. This is the theory behind running two brake light switches in parallel for your car.
The actual wiring would look something like this: One wire from your car’s original brake light circuit (the one that used to go to the single switch) would split and connect to the input terminal of both new switches. Then, a second wire would run from the output terminal of the first new switch, and a third wire would run from the output terminal of the second new switch. These two output wires would then be joined together and connected to the wire that originally went from your old single switch to the brake lights.
Here’s the kicker, and where the common advice often falls short: this setup can work, but it introduces complexities you might not anticipate. The primary issue is that you’re now dealing with two switches that are intended to operate independently but are sharing the same load (the brake light bulbs). Each switch has a certain resistance, and when you put them in parallel, their combined resistance is lower than either individual switch. This isn’t usually a problem for modern cars with relatively low-draw brake lights, but it’s something to be aware of.
A more significant problem is how you mount and activate these switches. A single brake light switch is usually actuated by the brake pedal arm itself. If you add a second switch, how do you make sure both switches are activated reliably by the pedal? You might need custom bracketry, linkage, or some clever mechanical arrangement. (See Also: Can Light Switches Fail )
Trying to get two separate physical switches to align perfectly with the brake pedal action is a headache. I tried mounting a second switch using a bent piece of metal as a lever, thinking it would work. What actually happened was one switch would engage slightly before the other, and often, neither would get a solid, consistent connection.
It was more fiddly than I expected, and the brake lights would flicker randomly. It wasn’t a reliable fix.
Real-World Scenarios: When Does Parallel Make Sense?
While the concept of running two brake light switches in parallel is appealing for redundancy, the practical application is often more complicated than it sounds. However, there are specific scenarios where this kind of thinking (if not the exact parallel switch setup) can be beneficial, especially when dealing with older or custom vehicles where standard parts don’t quite fit or when you’re really prioritizing ultimate reliability.
One of the main reasons people consider this is for custom builds or hot rods. In these cases, original wiring might have been modified, or the builder wants to make sure even more solid lighting. For instance, if you’ve installed extremely bright LED brake lights, you might have a dedicated relay for them.
In such a setup, you could potentially use two smaller, simpler switches (like momentary push buttons) in parallel to trigger the relay. The relay itself handles the high current, and the switches just provide a low-current signal. This bypasses the issue of switch resistance and activation.
I saw this done on a custom motorcycle build once, where two small, sealed buttons were mounted discreetly, wired in parallel to trigger the relay for the LED brake lights. It looked clean and was incredibly reliable because the switches themselves weren’t carrying the main load.
Another angle is in situations where a single switch is prone to moisture or extreme environmental exposure. If your brake light switch is located in a spot that constantly gets sprayed with water or mud, a single switch might fail repeatedly. You could try to mount two switches in parallel, perhaps one in the more exposed original location and a second one in a more protected spot, wired to activate simultaneously.
However, this still runs into the mechanical activation problem I mentioned earlier. Getting two distinct physical switches to trigger from a single pedal arm, reliably and at the same time, is the primary hurdle. It often requires custom fabrication that might cost more time and money than simply using a high-quality, sealed aftermarket switch designed for harsh environments.
A more common and often more sensible alternative to parallel switches is using a single, higher-quality switch. Many OEM switches are designed to be quite solid, but aftermarket options exist that are sealed and built for longevity.
For example, some industrial-grade switches or even marine-grade components might offer better resistance to corrosion and wear than a standard automotive brake light switch. Instead of wrestling with two switches, I’d spend my time hunting for one really good, dependable switch. I once sourced a heavy-duty, triple-sealed switch for a Jeep that spent a lot of time off-road. It cost about $60, which was double the price of a standard one, but it lasted for years without a hiccup, whereas the cheap ones I’d used before would fail every 8-12 months.
That taught me a valuable lesson about investing in quality over complex redundancy.
Ultimately, the decision to use parallel switches hinges on your specific vehicle, your mechanical skills, and the desired outcome. For most everyday cars, the complexity and potential for unreliable activation make it a less attractive option than simply making sure you have a correctly installed, good-quality single switch. The real-world use cases often involve custom setups where standard solutions aren’t an option, or where the switches are controlling a relay rather than the lights directly.
Common Mistakes and What to Watch Out For
When people start thinking about running two brake light switches in parallel, they often jump straight to the wiring diagram without considering the physical realities. This is where most DIYers stumble. The biggest mistake is assuming that two switches will magically sync up with the brake pedal.
Most brake light switches are activated by a plunger or lever that’s pushed by the brake pedal arm. If you have two separate switches, you need a way to make sure both plungers are depressed simultaneously and fully when the pedal is pressed. This often requires custom brackets, rod extensions, or complex lever systems.
Without proper alignment, one switch might engage too early, too late, or not at all, leading to intermittent brake lights or no brake lights when you need them most. (See Also: Do All Red Light Switches Have Dimmer )
Another common pitfall is overlooking the current draw. While the brake light bulbs themselves don’t draw a massive amount of current, having two switches wired in parallel means the total current is flowing through two sets of contacts. If the switches aren’t rated for the combined load, or if the wiring connections are poor, you can experience overheating, melting, or even a fire hazard.
I once saw a setup where someone had used two tiny toggle switches, assuming they’d work fine. The plastic around the terminals started to melt within a week. They looked like they were designed for a doorbell, not for the electrical demands of a vehicle.
Always check the amperage rating of your switches and make sure they can handle the load, or better yet, use them to trigger a relay.
Mixing different types of switches is another mistake. If you use one old switch and one brand-new one, or two switches with different contact types (e.g., one normally open and one normally closed, though this is less common for brake lights), you can create electrical imbalances. This can lead to one switch failing prematurely or the circuit not functioning correctly. It’s best to use two identical switches if you’re going this route, or ideally, a single, high-quality replacement.
People also forget about the return spring action of the brake pedal. When you release the pedal, the switch plunger needs to retract cleanly. If your parallel setup creates any binding or resistance, the plunger might not retract fully, keeping the brake lights on. This happened to me once; I had a jury-rigged system that worked for a bit, but when I released the pedal, one of the switches didn’t pull back completely. The brake lights stayed dimly lit, and I only noticed because I could smell a faint electrical odor. It turned out the plunger was sticking. It took me ages to figure out it wasn’t a wiring issue but a mechanical one.
Finally, there’s the temptation to overcomplicate the wiring. While the idea is redundancy, adding too many extra wires, splices, and connections can create more points of failure than you started with. Every crimp, every twist, every butt connector is a potential place for corrosion or a loose connection down the line. Keeping the wiring as clean and straightforward as possible is always the best approach, even when adding a second switch.
The Case Against Simple Parallel Switches: My Own Experience
Okay, let’s talk frankly. Everyone says, ‘just get a new switch.’ And 99% of the time, they’re right. But I’m the type who likes to push things, to see if there’s a ‘better’ way, a more solid way. So, I decided to tackle the parallel brake light switch idea head-on, specifically on my old Jeep Cherokee. The stock switch was an absolute pain, located under the dash where you can barely see it, let alone get a wrench on it.
My brilliant plan was to install the standard switch in its usual spot, but add a second, identical switch mounted slightly higher up, activated by a small bracket I fabricated that would push both plungers simultaneously when the pedal arm moved. I spent a solid afternoon mocking up the bracket. It involved drilling, bending metal, and a lot of trial and error to get the alignment just right. The goal was that when the pedal arm hit the bracket, it would depress both switches equally. I wired them in parallel, thinking, ‘If one ever fails, the other will pick up the slack. Genius!’
For about three days, it was glorious. My brake lights worked perfectly. Then, one morning, I got in the Jeep, and nothing. No brake lights. At all. Panic. I checked the fuse – good. I checked the bulbs – good. I started tracing wires, and this is where the frustration kicked in. Was it the primary switch? The secondary switch? A bad connection between the two? The whole point was simplicity and reliability, and I had created a diagnostic nightmare.
After about an hour of wiggling wires and banging on the pedal, the lights flickered on, then off again. It turned out the issue wasn’t a single switch failure, but a combination of things.
One of the switches, likely due to the slightly uneven pressure from my homemade bracket, had a slightly weaker connection than the other. This meant that under certain vibration conditions, it would lose contact.
Because they were in parallel, this single faulty connection was enough to break the entire circuit. It was a classic case of the cure being worse than the disease.
I ended up ripping out the whole contraption, fabricating a proper mount for a single, good quality aftermarket switch, and calling it a day. It cost me a weekend and about $75 in parts and wasted time, all because I thought I could outsmart a simple electrical circuit.
The lesson learned? Sometimes, the simplest solution is the best. For most of us, the best approach is to make sure the single brake light switch is properly installed, functioning, and of good quality. If you’re building a custom vehicle or have very specific needs, then yes, you might explore more complex solutions, but for the average car owner, trying to run two switches in parallel is often more trouble than it’s worth. The common advice to just replace the single switch is usually spot-on.
Practical Tips for Brake Light Switch Replacement (and Beyond)
Replacing a brake light switch, whether you’re sticking with a single one or contemplating a more complex setup, often involves a bit of fiddly work. First off, identify the switch. It’s usually a small plastic component, often with a plunger, mounted on the brake pedal support bracket. You’ll likely need a flashlight and possibly a mirror to get a good look at it. Sometimes, you can reach it from under the dash, while other times, you might need to remove a panel or two for better access. My ’98 Accord required removing a kick panel, which was a pain but made the job manageable. (See Also: Can Light Switches Have Cameras In Home Walls )
Once you’ve located it, disconnect the electrical connector. It usually has a small tab you need to press. Then, you’ll need to remove the old switch. Some screw in, others have a locking clip, and some just pull out. If it’s a screw-in type, you might need a deep socket or a specific wrench. For my old Subaru, it was a simple quarter-turn twist-and-pull. If you’re replacing it, make sure you have the new switch handy to see how the old one comes out. A little preventative maintenance here goes a long way; before you remove the old switch, spray some penetrating oil around its base if it looks corroded or stuck. Let it sit for a few minutes.
If you are indeed trying to wire two switches in parallel, here’s a practical approach that might work better than my previous attempts, but still comes with caveats. Instead of two separate physical switches, consider using a single, heavy-duty switch that has two separate sets of contacts (often called DPDT – Double Pole, Double Throw – or SPDT with multiple outputs). You would wire your power input to the common terminal. Then, you could wire your output to the brake lights from one set of contacts, and duplicate that output from the second set of contacts.
This way, you have redundancy within a single, solid unit. You’d still need to make sure your brake pedal actuates this switch reliably. This is a much cleaner approach than trying to align two separate mechanical plungers. I’ve seen industrial-grade switches with this kind of dual-contact setup, and they are far more reliable than trying to jury-rig two separate switches.
Another tip, especially for those tempted by the parallel idea for reliability: don’t underestimate the power of a good relay. If you’re installing aftermarket LEDs or just want extra security, wire your brake light switch (or switches) to trigger a relay. The relay then handles the actual power to the bulbs. This protects your switches from carrying high current, extending their life and reducing the risk of overheating. You’d have your switch(es) sending a low-voltage signal to the relay’s coil, and the relay’s heavy-duty contacts would handle the main power flow to the brake lights. This is a standard practice in automotive electrical work for a reason – it works, and it’s reliable.
Finally, always test your work. After installing a new switch or modifying the wiring, get a friend to stand behind the car (safely, with their foot on the brake) while you press and release the pedal. Make sure the lights come on when you press and go off when you release, every single time. Check for any flickering or dimming.
If you’ve gone the parallel route, test each switch independently if possible, or at least cycle the pedal many times to see if any intermittent issues arise. If you’re unsure about any part of the process, it’s always better to consult a qualified mechanic or an automotive electrician.
Sometimes, paying an expert for an hour of their time saves you a weekend of frustration and potential damage.
Faq: Can I Run Two Brake Light Switches in Parallel?
Can I Wire Two Brake Light Switches Together?
Yes, you can wire two brake light switches together in parallel. This means connecting the power input terminals of both switches together, and then connecting the power output terminals of both switches together. The combined output then goes to your brake lights. The intention is that if one switch fails, the other will still allow power to flow to the brake lights.
Is It a Good Idea to Have Two Brake Light Switches?
While it’s technically possible to have two brake light switches, it’s generally not a good idea for most standard vehicles due to practical complications. It’s difficult to make sure both switches are activated reliably and simultaneously by the brake pedal, and it can create more points of failure. A single, high-quality, properly installed switch is usually a more reliable solution.
What Happens If I Wire Brake Light Switches in Parallel Incorrectly?
If you wire brake light switches in parallel incorrectly, you could end up with no brake lights at all, intermittent brake lights, brake lights that stay on constantly, or even overheating and fire hazards if the switches or wiring are not rated for the current. Mechanical issues with how the pedal actuates both switches are also common, leading to unreliable operation.
Can One Brake Light Switch Control Two Bulbs in Parallel?
Yes, a single brake light switch is designed to control multiple brake light bulbs, which are wired in parallel to each other within the vehicle’s lighting system. The switch sends power to the circuit, and then the bulbs on that circuit light up. The switch itself doesn’t control each bulb individually but rather the entire brake light circuit.
Conclusion
So, can I run two brake light switches in parallel? The short answer is yes, you can, but whether you should is a much bigger question. For the vast majority of cars and trucks out there, the complexity of getting two physical switches to work reliably with your brake pedal outweighs any perceived benefit of redundancy. I’ve learned the hard way that a poorly implemented parallel setup can be far more problematic than a single, well-functioning switch.
My advice? Focus on sourcing a high-quality, properly rated single brake light switch for your vehicle. If you’re dealing with a custom build or have very specific requirements, then exploring options like using a relay triggered by a switch, or a single switch with dual contacts, might be a more sensible path to achieving redundancy without the headaches.
Ultimately, reliable brake lights are a must for safety. Don’t compromise that for a complicated fix. If you’re unsure about the wiring, or if you’re looking at a custom setup, it’s always worth your time and safety to consult a professional. For most of us, though, a good quality single switch is the way to go. Think about what your car actually needs before you dive into parallel wiring, and save yourself some headaches.
