1950-1959 Buick Roadmaster Brake Light Switch: A Comprehensive Guide
Everything Roadmaster owners need to know about diagnosing and replacing the hydraulic brake light switch.
- The 1950-1959 Roadmaster uses a hydraulic pressure switch, not a mechanical one by the pedal.
- Failure symptoms are simple: brake lights don't work, or they stay on constantly.
- Replacement is a simple DIY task, but you must work quickly to avoid letting air into the brake lines.
- If lights don't work after installing a new switch, try bleeding the air directly from the switch fitting.
Diagnosing a Faulty Brake Light Switch
A failing brake light switch on your classic Roadmaster typically shows one of two signs: your brake lights don't work at all, or they stay on constantly. If the switch fails in the 'open' position, your lights won't turn on, which is a critical safety issue. If it fails in the 'closed' or shorted position, the lights will remain on even when you're not braking, which can drain your battery and confuse other drivers.
Before blaming the switch, always check the simple things first. Make sure the bulbs are good and check the brake light fuse. Also, be aware that power flows from the brake switch through the turn signal switch; a problem in the turn signal switch can sometimes prevent the brake lights from working correctly.
Brake Lights Stuck On?
If your brake lights are stuck on, it could be a bad switch, but it might also point to a problem in your hydraulic system. Issues like a blocked master cylinder return port or a collapsed rubber brake hose can trap pressure in the lines, keeping the switch activated. This requires a thorough inspection of the entire brake system.
Choosing the Right Aftermarket Switch
Since original GM parts for these vehicles are no longer in production, you will be choosing from aftermarket brands. For a part like this, reliability is more important than brand name recognition, as some modern hydraulic switches have a reputation for premature failure in classic cars. The two main brands you may encounter are Standard Ignition and Rostra Powertrain.
- Standard Ignition (SMP): A very common and long-established brand in the aftermarket world. They are generally considered a reliable, go-to choice for replacement electrical parts on a wide range of vehicles. For classic car owners, they are often the most readily available option.
- Rostra Powertrain: Rostra produces a wide variety of automotive electronics and claims their parts meet or exceed original specifications. While they are a known manufacturer, there is less specific feedback available from classic Buick owners regarding the long-term reliability of their hydraulic switches.
Pro Tip: Some owners of classic cars have experienced repeated failures with modern hydraulic switches. While this guide focuses on direct-fit parts, an alternative for those seeking maximum reliability is a custom conversion to a mechanical switch mounted at the brake pedal, though this requires modification.
Brake Light Switch Replacement Cost
Replacing the brake light switch is an inexpensive job. The part itself is affordable, and labor at a shop should be minimal. The main cost driver for professional installation will be the shop's minimum labor charge, typically a half-hour or one hour.
| Part/Service | Estimated Cost |
|---|---|
| New Aftermarket Switch | $10.92 - $19.74 |
| Shop Labor | $60 - $120 |
| Total Estimated Cost | $71 - $140 |
Frequently Asked Questions
Where is the brake light switch located on my Roadmaster?
The switch is located under the hood, screwed into a brake line junction block on the driver's side frame rail, often near the master cylinder. It is not inside the car by the brake pedal.
Can I replace this switch myself?
Yes, this is a DIY-friendly job for those comfortable working with brake fluid. The key is to work quickly. Have the new switch ready to install the moment you remove the old one to minimize fluid loss and air entry. A wrench and some rags are the primary tools needed.
My new switch is installed, but the lights still don't work. What's wrong?
It's possible a small amount of air got trapped in the switch during installation. Have a helper press and hold the brake pedal. Then, slightly loosen the switch until a little fluid seeps out, and immediately retighten it. This should bleed the trapped air. If that doesn't work, re-check your wiring and the fuse.
Do I need to bleed my brakes after replacing the switch?
If you replace the switch quickly, you can often avoid a full brake bleed. However, if the brake pedal feels spongy or soft after the replacement, it means a significant amount of air has entered the system, and you will need to bleed the brakes properly.
Technical Specifications
Hydraulic Pressure Activated, 1/8-NPT Thread, 2-Terminal Electrical Connector
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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.