Studebaker M5 Brake Light Switch Guide: 1941-1948
Keep your classic M5 truck safe and on the road by understanding its unique brake light switch.
- The 1941-48 Studebaker M5 uses a hydraulic pressure switch, not a mechanical one at the pedal.
- The most common failure is brake lights not working at all, which is a critical safety hazard.
- If you use modern DOT 5 silicone brake fluid, the original-style hydraulic switch may fail quickly.
- Replacement is an easy DIY job, but you must bleed the brakes afterward to ensure safety.
Understanding the M5's Hydraulic Switch
If your brake lights have stopped working, the brake light switch is a common culprit. The hydraulic pressure switch design on the 1941-1948 M-Series truck was typical for its time but has known reliability issues. These switches can fail over time, sometimes requiring very hard pedal pressure to activate, which is a major safety hazard. They can also leak brake fluid or fail internally, causing the lights to stay on or not work at all.
Warning for Silicone Brake Fluid Users
Many classic truck owners upgrade to DOT 5 silicone brake fluid. Be aware that original-style reproduction hydraulic brake light switches are known to fail quickly when used with silicone fluid. If you use DOT 5 fluid, converting to a universal mechanical switch is a more reliable long-term solution, though it requires custom installation.
Symptoms of a Failing Brake Light Switch
On a classic truck like the M5, there is no dashboard warning light to tell you the switch is bad. You must rely on checking the lights yourself. The symptoms are usually very clear.
- Brake Lights Do Not Turn On: This is the most dangerous symptom. If you have already checked the bulbs and the fuse, the switch is the most likely cause. The internal parts have likely failed and no longer complete the circuit.
- 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 will drain your battery and confuse other drivers.
- Delayed or Intermittent Lights: A failing switch may require more and more brake fluid pressure to activate. This means your lights might only come on during hard stops, not during gentle braking.
Choosing the Right Aftermarket Switch
Original factory parts for this truck are no longer made. Your choice is between a new aftermarket reproduction switch and a New Old Stock (NOS) part. Aftermarket switches are the most practical and widely available option.
- Standard Ignition (Standard Motor Products): This is a common, reputable brand for this part. It is widely available from many auto parts sellers and is considered a reliable replacement for the original switch.
- Rostra Powertrain: While a known aftermarket brand, there is no search-verified evidence of them making a direct-fit hydraulic switch for the Studebaker M5. Stick with brands confirmed to fit.
- New Old Stock (NOS): Finding a true NOS Studebaker switch is very rare. Even if found, rubber seals inside can become brittle and fail with age, making a new aftermarket part a safer bet.
Pro Tip: Consider a Mechanical Switch Upgrade
For long-term reliability, many Studebaker owners modify their trucks to use a universal mechanical brake light switch. This type of switch is activated by the physical movement of the brake pedal arm. It requires fabricating a small bracket and re-routing the wires, but it eliminates the problems with hydraulic switches and silicone fluid.
| Part Type | Price Range | Notes |
|---|---|---|
| New Aftermarket (Hydraulic) | $10.92 - $38.97 | Most common and practical choice. Brands like Standard Ignition are readily available. |
| New Aftermarket (Mechanical Kit) | $15 - $40 | A reliable upgrade but requires custom installation. |
| Shop Labor | $75 - $150 | Includes installation and bleeding the brakes. |
Frequently Asked Questions (FAQ)
Where is the brake light switch located on my Studebaker M5?
The brake light switch is not inside the cab by the pedal. It is a hydraulic pressure switch screwed into the master cylinder or a nearby brake line junction block. You will need to look under the truck to access it. It will have two wires connected to it.
Is replacing the brake light switch a difficult job?
No, for a DIYer, this is an easy job. You disconnect the two wires, unscrew the old switch, and quickly screw the new one in to minimize brake fluid loss. However, you must bleed the brakes after replacement to remove any air that entered the system. This is a critical safety step.
How do I test my M5's brake light switch?
First, confirm your bulbs and fuse are good. Then, locate the switch and unplug the two wires. Carefully use a jumper wire to connect the two wire terminals together. If the brake lights turn on, the switch is bad. If they do not light up, you have a problem elsewhere in the wiring.
Are there any recalls for the Studebaker M5 brake light switch?
No. There are no NHTSA recalls or Technical Service Bulletins (TSBs) for the brake light switch on a 1941-1948 Studebaker M5. This is normal for a vehicle of this age.
Technical Specifications
OEM Part Numbers: 193032
This is a hydraulic pressure-activated switch. The common thread size is 1/8-27 NPT. It is designed to activate when brake line pressure reaches approximately 60-120 PSI.
We Have This Part in Stock
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.