Killswitch LED & Voltage Compatibility Guide

At Iron Age Guitar Accessories, we often get questions about powering LED killswitches and what battery setups are compatible. While adding an illuminated switch can be a great upgrade, making sure your LED is matched to your guitar’s power system is crucial for both safety and performance. In this article, we want to lay out everything you need to know in a clear, accessible way—so you’ll know exactly what works and what doesn’t. We’ll be sharing our hands-on testing results, resistor recommendations, and some common pitfalls to avoid.

Most importantly, never connect a 9V battery or higher directly to the LED, as this will instantly burn it out (they are only rated for just under 3v). Let’s dive into the details and make sure your next LED install is smooth and trouble-free.

Power Source Compatibility for LED Killswitches

CR2032 Batteries: Direct Power, No Fuss

If your guitar is equipped with a CR2032 coin cell battery or you’re considering a standalone LED circuit, you’re in the ideal situation for a simple and reliable install. Through extensive hands-on testing, we’ve found that most standard indicator LEDs can be powered directly from a CR2032 battery without the need for any additional resistor.

The voltage and current output of the CR2032 are low enough that you won’t risk burning out your LED or overheating any wiring. In our experience, this setup provides long battery life (equal to that of a 9v) and consistent brightness, making it a great choice for anyone looking for a straightforward LED killswitch upgrade.

This means you only need the LED switch & battery—no extra components or calculations required. It’s a true plug-and-play solution that’s both safe, effective, and saves  on space.

>CR2032 Installation Kits For Killswitches Available Here<

9V Systems: The Standard (With a Simple Addition)

18V & 24V Systems: Higher Voltage, Special Considerations

Some guitarists opt for 18V or even 24V mods, usually by wiring two or more 9V batteries in series to power their active pickups or preamps. These modifications are popular for increasing headroom and dynamic range, giving your instrument a bit more punch and clarity. When it comes to adding an LED killswitch to these higher-output systems, things get a bit trickier.

In our own testing, we wanted to see what would happen outside the usual recommendations, so we tried running two 150Ω resistors in series. The result was a lot of heat—enough to melt heat shrink tubing and pose a safety risk. To find a better solution, we tested a large Allen Bradley vintage 750Ω 1-watt resistor, and it performed sufficiently well: after 20 minutes of continuous use, it was only slightly warm and kept the LED shining bright. Based on these results, we recommend using at least a 750Ω resistor rated for 1 watt or higher for both 18V and 24V systems to properly manage heat and protect your components.

It’s worth noting that while these resistor values are under the typical recommended spec, they provide the brightest possible LED output without compromising safety in our experience. We’re also in the process of sourcing modern 820Ω 1-watt resistors, which will add an extra margin of safety while still delivering strong brightness. If you have an 18V or 24V setup, just let us know in your order notes and we’ll include one of these resistors free of charge.

Like with 9V systems, you can share the power source between your active electronics and the LED, but the higher voltage means the wiring and resistor choice become even more critical. Sometimes, integrating the LED with these complex power setups can be a bit more involved, so for the simplest and safest results, we recommend using a separate, dedicated battery—like a CR2032—just for the LED. This avoids any complications and ensures your killswitch operates flawlessly. If you have any questions or need guidance, we’re always here to help you make the right choice for your rig.

Quick Reference: LED Killswitch Power & Resistor Compatibility

All our recommendations are based on nearly a decade of real-world testing and reliable use in the field. We prioritize maximum brightness while ensuring safety and durability, and have never encountered issues with these values in practice.

For those who want extra peace of mind, you can always use the official recommended resistor values—just remember that we always advise a 1-watt resistor or larger for better heat dissipation, even if the official specs call for a smaller size.

In Closing

As a quick reminder, here are a few of the most common questions and troubleshooting tips we share with our customers:

• Always double-check your LED polarity if it doesn’t light up—LEDs are directional and won’t work if wired backwards.
• Disconnect all power sources before doing any wiring or soldering to prevent accidental shorts or damage.
• If you’re ever unsure about your setup or which resistor to use, don’t hesitate to reach out—we’re always happy to help you get it right.

If you need a larger 820Ω resistor for your 18V or 24V system, just let us know in the “Order Notes” section at checkout. While this note won’t appear on your receipt, rest assured we see it on our end and will include the correct resistor with your order.

Remember, all Iron Age switches are covered by our 360-day warranty—a standard we set, and while others may try to copy, they can’t match our real-world experience, data, or commitment to your satisfaction and support.

If you have any questions or need personalized advice, just drop us a message. We’re here to help you make your next killswitch install smooth, safe, and reliable.

- Alex

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