12v/24v question

thoner7 · Thursday at 3:25 PM

I want to add a rear ‘cyclops’ run/stop light to my truck. Is it possible to use a 12v light in the 24v system, if I swap the bulbs over to LED? 24v uses thinner wiring, so the rest of the housing should be good, right? The LED should drop the amperage pulled and would be compatible with 24v.

At least that’s what I’m thinking

TOBASH · Thursday at 3:59 PM

You would need to run a power inverter with 24 to 12 V that is always on. When you activate the brake pedal, that would serve to turn off the power.

It sounds backwards however the other way around, there is a delay between actuation so when you hit the brake, the lights won’t go on right away if you keep the brake light on constant off with signal to turn on.

There are constant on switches that you can use to easily make this work.

The “electrical” part of this steel soldiers forum/family will be able to tell you exactly what to order.

Start a thread there. Awesome knowledgeable members there.

thoner7 · Thursday at 4:44 PM

Why wouldn’t I be able to tie into the run/stop feature of the tail light?

98G · Thursday at 5:02 PM

I see no

thoner7 said:
I want to add a rear ‘cyclops’ run/stop light to my truck. Is it possible to use a 12v light in the 24v system, if I swap the bulbs over to LED? 24v uses thinner wiring, so the rest of the housing should be good, right? The LED should drop the amperage pulled and would be compatible with 24v.

At least that’s what I’m thinking

I see no reason this wouldn't work.

Milcommoguy · Thursday at 7:43 PM

This is very easy to do

thoner7 said:
I want to add a rear ‘cyclops’ run/stop light to my truck. Is it possible to use a 12v light in the 24v system, if I swap the bulbs over to LED? 24v uses thinner wiring, so the rest of the housing should be good, right? The LED should drop the amperage pulled and would be compatible with 24v.

At least that’s what I’m thinking

Easy Peeze.... These types of requests... are outside of the standard HumV's limited wiring needs, BUT your custom brake light setup will not break the bank and work the way you asked with a simple modified connection. Note: This write-up was design to NOT work in the military "Blackout" condition, which is a good thing, as I am following the military lighting protocols.

This is very easy to do.... NO need for any converters, switches or backwards thinking. Just a long piece of wire, say 14 gauge to route from the headlight switch and the 24 volts to instantly signal your intent to STOP when mashing the pedal. (check to be sure of LED voltage & or the bulb to be 24 Volts)

Here we GO... Remove the large connector, back of the headlight switch. Of all the wires, locate wire tag number 22A. You will need to tap into this lead. It is the common brake light circuit in the "STOP LIGHT or SerVice Drive" position.

Run the wire to the location of your ‘cyclops’ light and note this is the positive lead. You will need provide a ground to the other lamp lead. (some LED lighting may have a RED & Black wires making this even easier ???) Incandescent bulbs the socket ground, center pin positive) This statement is a bit wordy... but just want to clarify...CUZ I don't know what you got, CUZ

Total cost ??? A couple of bucks for the wire, a way to tap into the 22A lead, some time to route the wire front out around down over under to the back and a ground connection and the cyclops’ light. That's all you need and some time.

Some may have a better way.... Some.

The HumV and its single filament STOP & TURN design makes for IMO this the simplest, straightforward and cheap and done. Follow all good practice of routing wires, connections.

The “electrical” part by, CAMO

thoner7 · Thursday at 10:07 PM

Sh

Milcommoguy said:
This is very easy to do

Easy Peeze.... These types of requests... are outside of the standard HumV's limited wiring needs, BUT your custom brake light setup will not break the bank and work the way you asked with a simple modified connection. Note: This write-up was design to NOT work in the military "Blackout" condition, which is a good thing, as I am following the military lighting protocols.

This is very easy to do.... NO need for any converters, switches or backwards thinking. Just a long piece of wire, say 14 gauge to route from the headlight switch and the 24 volts to instantly signal your intent to STOP when mashing the pedal. (check to be sure of LED voltage & or the bulb to be 24 Volts)

Here we GO... Remove the large connector, back of the headlight switch. Of all the wires, locate wire tag number 22A. You will need to tap into this lead. It is the common brake light circuit in the "STOP LIGHT or SerVice Drive" position.

Run the wire to the location of your ‘cyclops’ light and note this is the positive lead. You will need provide a ground to the other lamp lead. (some LED lighting may have a RED & Black wires making this even easier ???) Incandescent bulbs the socket ground, center pin positive) This statement is a bit wordy... but just want to clarify...CUZ I don't know what you got, CUZ

Total cost ??? A couple of bucks for the wire, a way to tap into the 22A lead, some time to route the wire front out around down over under to the back and a ground connection and the cyclops’ light. That's all you need and some time.

Some may have a better way.... Some. The HumV and its single filament STOP & TURN design makes for IMO this the simplest, straightforward and cheap and done. Follow all good practice of routing wires, connections.

The “electrical” part by, CAMO

Wouldn’t I be able to just tap into the stop wire (22a?) at one of the rear tail lights?
Also, aren’t the running lights a separate wire/blub? I’ll have to look at my truck and see if it’s the same bulb that just illuminates brighter

Milcommoguy · 2025-10-24T01:22:37-0400

thoner7 said:
Sh

Wouldn’t I be able to just tap into the stop wire (22a?) at one of the rear tail lights?
Also, aren’t the running lights a separate wire/blub? I’ll have to look at my truck and see if it’s the same bulb that just illuminates brighter

I explained it the way it works. Running lights are the little bulb, wasn't part of stopping light plan??? The other fat bulb not counting the blackout bulbs is a single circuit, one wire, STOP & TURN. All of the magic or logic is handled in the Turn Signal Selector for the light/s to be a STOP or a TURN. (or emergency warning)

If you think connecting to the 22a wire... when turning..."cyclops" will be blinking Good for the right... how are you going to handle the left side. It could be done with a couple of diodes (and I left that design out due to the turning issue of a blinking center lamp and ............)

I am going to stop here and turn it over to you, CAMO

TOBASH · 2025-10-24T02:52:59-0400

Cam… your front signal unit must use some similar tech.

Also I guess he could purchase dual voltage LED that function on both 12 and 24 Volts.

DREDnot · 2025-10-24T03:09:58-0400

Why does it have to be 12V?

Just tap off any part of that circuit and use 24V bulbs.
No need to add complexity

thoner7 · 2025-10-24T09:52:05-0400

DREDnot said:
Why does it have to be 12V?

Just tap off any part of that circuit and use 24V bulbs.
No need to add complexity

well that’s my question. If I buy a 12v light, housing, wiring and all, and switch to a 24vLED bulb, will the rest of the housing/wiring/be ok?

I specifically say LED because the amp draw could be as little as 20mA. So even though it’s double the voltage, I’ll still be well under the rated wattage for the fixture.

I don’t fully grasp electrical stuff tho so maybe I’m totally wrong.

according to to “fake intelligence” it’s safe :

AI says- It is safe and generally better to run 24V through wiring designed for 12V, provided you are powering a 24V light bulb of the same wattage or less. Standard low-voltage wire insulation (like automotive wire) is typically rated for at least 50V, which is well above 24V. | The 24V poses no threat to the insulation of the 12V-rated wire. If you use a 24V bulb with the same wattage (e.g., 50W) as the 12V bulb it replaces, the 24V circuit will draw half the current (Amps). | The 12V wiring is over-specified for the new, lower current, making it very safe from overheating.

thoner7 · 2025-10-24T10:01:17-0400

Milcommoguy said:
I explained it the way it works. Running lights are the little bulb, wasn't part of stopping light plan??? The other fat bulb not counting the blackout bulbs is a single circuit, one wire, STOP & TURN. All of the magic or logic is handled in the Turn Signal Selector for the light/s to be a STOP or a TURN. (or emergency warning)

If you think connecting to the 22a wire... when turning..."cyclops" will be blinking Good for the right... how are you going to handle the left side. It could be done with a couple of diodes (and I left that design out due to the turning issue of a blinking center lamp and ............)

I am going to stop here and turn it over to you, CAMO

Ok thanks for clarifying. I hadn’t dove into the wiring aspect yet, wanted to order a light first.

I can bypass the turn function by connecting to the wire before it hits the turn signal, it at the three lever switch.

I think I can get a running light right at the left tail light, but I’ll research and play with that later.
Thank you.

thoner7 · 2025-10-24T10:18:44-0400

I was just able to dissect a broken tail light I had laying around. I may be able to just transplant the guys of it into a new housing too, but I won’t if it’s not necessary

Here is the light I was thinking, it’ll fit inside the hub diameter of the spare tire.

Motorcycle Stop Lens Rear Brake Tail Light Lamp For 28-31 Ford Model A Chopper | eBay

Features: Here's a simple but cool tail light for your motorcycle Replica of For 28-31 Ford Model A Taillight Can be custom fit for rear or side mounted setups Modern and Stylish Specification: Condition: 100% Brand New Color: chrome Lens: Red, Glass It is made from quality deep drawn stainless...

www.ebay.com

Coug · 2025-10-24T12:36:20-0400

The wires don't care what the voltage is, as long as the insulation is rated for it. All wire size really determines is amount of amps you can run without causing the wire to heat up. Higher voltage actually means you can run increased watts output overall.

The housing and related parts also don't care. The only time you start running into issues with higher voltages is when you have something making/breaking the electrical connection, which causes an arc. Higher voltage is bigger arc, so more wear and tear if the device isn't rated for the voltage. This is why those chinesium keyed start switches don't last long.

As long as you aren't changing the output wattage dramatically (and in this case you are lowering it by going LED) there should be zero issues repurposing a 12V housing for a 24V application.

thoner7 said:
*SNIP*

I think I can get a running light right at the left tail light, but I’ll research and play with that later.
Thank you.

That is how most of the license plate lights get their power; they use a 3 way connector to add an additional circuit path at the left brake light housing running light circuit.

12v/24v question

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thoner7

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TOBASH

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98G

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Motorcycle Stop Lens Rear Brake Tail Light Lamp For 28-31 Ford Model A Chopper | eBay

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