A Guide to the 1940-1949 Buick Roadmaster Series 70 Brake Light Switch
Keep your classic Buick's brake lights working correctly and safely with the right replacement switch.
- The brake light switch on your Roadmaster is a hydraulic pressure switch, not a mechanical one.
- Replacement is a critical safety repair; driving without working brake lights is illegal and dangerous.
- You MUST bleed the brakes after replacing the switch to ensure safe brake operation.
- Quality aftermarket brands like Standard Ignition are a reliable and affordable choice for this part.
Symptoms of a Failing Brake Light Switch
A bad brake light switch on your Roadmaster will show clear symptoms. The most critical is when your brake lights don't turn on at all. You should also watch for brake lights that stay on even when you're not braking, which can drain your battery. Finally, if the lights flicker or only work sometimes, the switch is likely failing and needs to be replaced. Before replacing the switch, always check the bulbs and fuses first to rule out simpler issues.
Critical Safety Component
A faulty brake light switch is a major safety hazard. Driving without functioning brake lights is illegal and dramatically increases the risk of a rear-end collision. Address any brake light issues immediately.
Choosing the Right Aftermarket Part
For a classic vehicle like the 1940-1949 Roadmaster, new original equipment (OEM) parts are no longer in production. Your options are typically New Old Stock (NOS), used original parts, or new aftermarket replacements. While NOS parts can be found, their internal rubber components may be dried out and unreliable. New aftermarket parts from reputable brands are often the most practical and reliable choice for a simple component like a hydraulic brake switch.
Two common brands available for your Buick are:
- Standard Ignition (Standard Motor Products): A long-standing manufacturer with a generally good reputation in the classic car community for producing quality replacement parts that fit and function correctly.
- Rostra Powertrain: Another established aftermarket supplier. For a simple hydraulic switch, their products are generally considered a functional and affordable option.
For this specific part, a quality aftermarket switch is a dependable and cost-effective solution. The technology is simple, and brands like Standard Ignition have a proven track record.
A Note on Connectors
Original switches from the 1940s often used screw-on terminals for the wiring. Some modern replacement switches may have push-on (spade) terminals. Before ordering, check the connections on your existing switch to see if you need to install new connectors on your wiring harness for a proper fit.
Estimated Replacement Costs
Replacing the brake light switch is an affordable repair. The primary cost is the part itself, with minimal labor if you have it done professionally.
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Rostra, Standard Ignition) | $10.92 - $15.52 |
| New Old Stock (NOS) OEM | Highly variable, if found |
| Shop Labor | $50 - $100 |
Frequently Asked Questions (FAQ)
Where is the brake light switch located on my 1940-1949 Roadmaster?
The brake light switch is a hydraulic switch, typically located screwed into the master cylinder under the hood or at a junction block in the brake line system under the car. It is not a mechanical switch found at the pedal.
Is it difficult to replace the brake light switch myself?
The physical replacement is easy for a DIY mechanic; the switch simply unscrews. However, because it's part of the hydraulic brake system, you must bleed the brakes after replacement to remove any air that entered the lines. This step is critical for safety. If you are not comfortable bleeding brakes, this job is best left to a professional.
Do I need to bleed the brakes after replacing the switch?
Yes. Because this is a hydraulic pressure switch, replacing it involves opening the sealed brake fluid system. Air will enter the lines, which must be removed by bleeding the brakes to ensure they function safely and effectively.
Are there any recalls for this part?
No. Modern recall systems managed by the NHTSA were not in place for vehicles of this age. There are no official recalls or Technical Service Bulletins (TSBs) for the brake light switch on a 1940-1949 Buick Roadmaster.
Technical Specifications
Type: Hydraulic Pressure Switch; Thread: 1/8-NPT; Terminals: 2-Terminal (verify screw-on or push-on style)
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.