1975-1979 Buick Roadmaster Brake Light Switch Replacement Guide
Diagnosing and replacing the simple switch that controls your Roadmaster's brake lights.
- This part is not specific to the Roadmaster; it's a common GM part used in many 1970s vehicles.
- Failure is dangerous. Replace the switch immediately if your brake lights do not work.
- Replacement is very easy for a DIYer, with the main challenge being the awkward location under the dash.
- A quality aftermarket brand like Standard Motor Products (SMP) or ACDelco is a reliable and affordable choice.
Understanding the Brake Light Switch in Your Classic Buick
If you're looking for a brake light switch specifically for a "1975-1979 Buick Roadmaster," you might have trouble finding a part listed that way. That's because your station wagon shares its brake light switch with nearly all full-size General Motors cars from that era, including the Buick LeSabre, Electra, and Chevrolet Caprice. This is good news, as the part is common, affordable, and widely available.
The switch is mounted under the dashboard on the brake pedal support. It's a simple mechanical device with a spring-loaded plunger. Due to its age, the plastic can become brittle and the internal contacts can wear out, leading to failure.
Symptoms of a Failing Brake Light Switch
The signs of a bad brake light switch are usually very clear. You will likely experience one of two problems:
- Brake Lights Don't Turn On: This is the most dangerous symptom. The internal contacts of the switch have failed, and the circuit for the brake lights never gets completed.
- Brake Lights Stay On: The switch is stuck in the "on" position, either due to a mechanical failure or a missing stopper on the pedal. This will drain your battery and confuse drivers behind you.
- Cruise Control Won't Disengage: If the switch fails, it may not correctly send the signal to turn off your cruise control when you tap the brakes, which is a significant safety issue.
Choosing the Right Aftermarket Switch
For a simple part like this, you don't need to hunt down an expensive New Old Stock (NOS) GM part. A quality aftermarket switch will perform just as well. Here’s how the brands stack up:
- OEM-Tier (ACDelco): ACDelco is GM's own parts brand. Choosing an ACDelco switch gives you a part that is identical to the original. For this vehicle, it is a reliable choice if the price is right.
- Top-Tier Aftermarket (Standard Motor Products - SMP): Brands like Standard Motor Products specialize in electrical components and have a strong reputation for quality that often meets or exceeds OEM specs. They are an excellent and reliable choice for your Roadmaster.
- Store Brands (Duralast, etc.): Parts from major auto parts stores are generally reliable and come with a good warranty. They are a perfectly acceptable option for this repair.
Pro Tip: Avoid the cheapest, unbranded "white-box" parts from online marketplaces. The few dollars you save aren't worth the risk of poor-quality internal components that could fail prematurely.
Installation Overview
Replacing the brake light switch is an easy DIY job that requires basic tools. The biggest challenge is the uncomfortable position you'll need to be in to access it under the dashboard.
- Disconnect the negative battery terminal.
- Locate the switch on the brake pedal arm assembly under the dash.
- Unplug the electrical connector.
- Remove the switch from its mounting bracket. It is often held by a clip or a small bolt.
- Install the new switch and reconnect the wiring.
- Reconnect the battery and test the brake lights. You may need to adjust the switch's position slightly to ensure the lights activate and deactivate at the correct pedal travel.
| Item | Estimated Cost |
|---|---|
| New Aftermarket Switch (SMP, Duralast) | $10 - $25 |
| New OEM Switch (ACDelco) | $15 - $30 |
| Shop Labor | $50 - $100 |
Frequently Asked Questions
Is this a difficult repair to do myself?
No, this is a very easy repair for a DIYer. The part is easy to access and typically requires only simple hand tools. The most difficult part is working in the tight space under the dashboard.
What tools are required for the job?
You will likely only need a small socket set or a screwdriver. No special tools are required for this job.
Are there any recalls for the brake light switch on my Roadmaster?
No. Searches of the National Highway Traffic Safety Administration (NHTSA) database show no recalls or technical service bulletins (TSBs) related to the brake light switch for the 1975-1979 Buick Roadmaster.
My brake lights are stuck on. Is it definitely the switch?
Most likely, yes. However, before replacing the switch, check the brake pedal to make sure it is returning to its full upright position. Sometimes a small plastic or rubber stopper on the pedal arm that presses the switch can break or fall off, causing the lights to stay on.
Technical Specifications
OEM Part Numbers: 10170430 25551819 D1539J
Mechanical plunger switch, typically with 2 or 4 terminals depending on cruise control function. Mounts to brake pedal support bracket.
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.