1939 Studebaker L5 Brake Light Switch Guide
Keep your classic Studebaker safe and its brake lights dependable with the correct replacement switch.
- The 1939 Studebaker L5 uses a hydraulic pressure switch, not a mechanical one at the pedal.
- A faulty brake light switch is a critical safety failure; do not drive the vehicle if the lights are inoperative.
- Replacement is a straightforward task, but it is mandatory to bleed the brakes afterward to ensure safety.
- Standard Ignition is a readily available aftermarket brand for this vintage application.
Understanding the Hydraulic Brake Light Switch in Your L5
If your brake lights have stopped working, the switch is a common point of failure. On the 1939 Studebaker L5, this part is a pressure-activated switch located under the hood, not a mechanical button by the pedal. This design was typical for the era and relies on the hydraulic pressure from the brake fluid itself to function. These original-style switches can fail over time, sometimes leaking or requiring very hard pedal pressure to activate the lights.
Critical Safety Part
Functioning brake lights are essential for safe driving. If your brake lights are not working, the vehicle is unsafe and should not be driven until repaired. It is also illegal to operate a vehicle with inoperative brake lights.
Symptoms of a Failing Brake Light Switch
The signs of a bad brake light switch are usually very clear and present a significant safety risk.
- Brake Lights Do Not Turn On: This is the most common and dangerous symptom. When you press the brake pedal, the lights fail to illuminate, making it impossible for drivers behind you to know you are stopping.
- Brake Lights Stay On: The switch can fail in the "on" position, causing the brake lights to remain lit even when your foot is off the pedal. This can drain your battery, confuse other drivers, and lead to premature bulb burnout.
- Intermittent or Flickering Lights: The lights may flicker or only work when the pedal is pressed very hard. This indicates the switch is failing internally and is no longer reliable.
Choosing the Right Aftermarket Switch
For a vehicle as old as the 1939 L5, finding New Old Stock (NOS) OEM parts is nearly impossible. The most practical and reliable solution is a new aftermarket replacement. Standard Ignition (also known as Standard Motor Products or SMP) is a well-established brand that manufactures replacement switches for classic vehicles. Their parts are designed to be direct-fit replacements, ensuring they function like the original. Given the limited availability of parts for this classic truck, a quality aftermarket switch is the best and often only choice.
A Note on Brake Fluid
Some older reproduction switches were not designed for modern DOT 5 silicone brake fluid and could fail prematurely. The Standard Ignition switch is compatible with the conventional DOT 3 brake fluid that was original to your Studebaker. Always confirm fluid compatibility before installation.
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Standard Ignition) | $38.97 |
| New OEM (NOS) | N/A (Extremely Rare) |
| Used OEM | $20 - $50+ (Varies by condition) |
| Shop Labor | $100 - $200 |
Frequently Asked Questions (FAQ)
Where is the brake light switch on a 1939 Studebaker L5?
The brake light switch is a hydraulic pressure switch located under the hood. It is screwed directly into the master cylinder or a junction block in the brake lines and will have two wires connected to it.
Can I replace the brake light switch myself?
Yes, this is a feasible DIY job for someone with mechanical experience. The main challenge is that after you replace the switch, you must bleed the brakes to remove any air that entered the hydraulic system. This step is critical for safe brake operation.
Why do my brake lights stay on?
If your brake lights are stuck on, the internal mechanism of the hydraulic switch has likely failed in the closed or 'on' position. This requires immediate replacement of the switch.
Are there any recalls for the 1939 Studebaker L5 brake light switch?
No. There are no recalls, Technical Service Bulletins (TSBs), or NHTSA complaints for this part on a vehicle of this age. This is normal for vintage automobiles.
Technical Specifications
OEM Part Numbers: 666858
Hydraulic pressure-activated switch with two male bullet terminals. The typical 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.