1946-1947 Studebaker M15A Brake Light Switch Replacement Guide
Keep your classic Studebaker safe and its brake lights reliable with the right information.
- The M15A uses a hydraulic pressure switch on the brake line, not a mechanical switch at the pedal.
- Failure is a critical safety issue; common symptoms are no brake lights, or lights that are stuck on.
- A new aftermarket switch from a reputable brand like Standard Ignition is the most reliable replacement option.
- Replacement is a simple DIY task, but you MUST bleed the brakes afterward to ensure safety.
Understanding the Hydraulic Brake Light Switch on Your M15A
If the brake lights on your Studebaker M15A truck have stopped working, the brake light switch is a common and likely culprit. On these classic trucks, the switch is a pressure-activated sensor that screws into the brake system. This design was common for the time but has known reliability issues. The original-style hydraulic switches can fail, sometimes leaking brake fluid or requiring very hard pedal pressure to work.
Symptoms of a Failing Brake Light Switch
The signs of a bad brake light switch are usually straightforward and present a major safety risk. Look out for these common symptoms:
- No Brake Lights: The most dangerous symptom is when the brake lights do not turn on at all when you press the pedal.
- Brake Lights Stuck On: The switch can fail in the 'on' position, leaving your brake lights constantly lit. This will drain your battery and confuse other drivers.
- Delayed or Intermittent Lights: A worn switch may only work under hard braking, meaning it won't activate during gentle stops.
Choosing the Right Aftermarket Switch
For a vehicle from the 1940s, finding new original factory parts is not a realistic option. The choice is between a used original part, a New Old Stock (NOS) part if you can find one, or a modern aftermarket replacement. Given that the original design is a known failure point, a new aftermarket switch is the most reliable and practical solution.
Standard Ignition (SLS27/SLS27T): This is the most widely available aftermarket brand for your M15A. Standard Ignition (also called Standard Motor Products or SMP) is a well-regarded company that has been making quality parts for decades. Their switches are described as being made from high-grade materials like brass to ensure durability and a long service life, making them a solid choice for replacing the old switch.
A Note on Brake Fluid
Some owners of classic Studebakers have found that modern DOT 5 silicone brake fluid can cause reproduction hydraulic switches to fail early. The Standard Ignition switch is designed for use with standard DOT 3 brake fluid, which was original to the vehicle. Always confirm fluid compatibility before installation.
Brake Light Switch Replacement Cost for 1946-1947 Studebaker M15A
The cost for a new aftermarket brake light switch is very reasonable. The main additional cost would be shop labor if you do not perform the replacement yourself.
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Standard Ignition) | $38.97 |
| Shop Labor | $75 - $150 |
| New OEM | Not Available |
| Used OEM | $20 - $50+ (Varies) |
Pro Tip: How to Test Your Switch
Before buying a new part, you can perform a simple test. First, make sure your brake light bulbs and the fuse are good. Then, locate the switch on the master cylinder and unplug the two wires. Carefully use a small jumper wire to connect the two terminals on the wiring harness together. If your brake lights turn on, the switch is bad and needs to be replaced. If they don't, the problem is elsewhere in the wiring.
Frequently Asked Questions (FAQ)
Where is the brake light switch located on my Studebaker M15A?
The brake light switch is not inside the cab by the pedal. It is a hydraulic switch screwed into the master cylinder, which is located under the hood or floor, depending on your specific truck's configuration. It will have two wires connected to it.
Is it hard to replace the brake light switch myself?
For a DIY mechanic, this is a fairly easy job. It involves disconnecting the wires and unscrewing the old switch. The most important part of the job is that you must bleed the brakes after installing the new switch to remove any air that entered the lines. This step is critical for your safety.
Do I need any special tools to replace the switch?
You will need basic hand tools like a wrench to remove the old switch, and potentially a Phillips screwdriver for the wire terminals. The most important equipment will be for bleeding the brakes, which includes a brake bleeder wrench and a catch bottle for the old fluid.
Are there any recalls for the brake light switch on my truck?
No, there are no recalls or Technical Service Bulletins (TSBs) from the NHTSA for the brake light switch on a 1946-1947 Studebaker M15A. This is normal for a vehicle of this age.
Technical Specifications
OEM Part Numbers: 193032
Hydraulic pressure-activated switch with two screw-type terminals. The common thread size is 1/8-27 NPT.
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The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.