1975-1978 GMC C35 Brake Light Switch: An Owner's Guide
Everything you need to know about replacing the brake light switch on your classic GMC C35 pickup.
- A failing brake light switch is a critical safety issue that must be addressed immediately.
- The most common symptoms are brake lights that don't work at all or stay on constantly.
- Replacement is a simple, low-cost DIY job that can be done with basic tools in under 30 minutes.
- Aftermarket brands like Standard Ignition offer reliable, high-quality replacements for this part.
Is Your Brake Light Switch Failing?
A bad brake light switch on your GMC C35 is more than an inconvenience; it's a serious safety hazard. Since these trucks have a simple electrical system, the signs of failure are usually straightforward. Ignoring them can lead to a dead battery or, worse, a rear-end collision.
Key Symptoms of a Bad Switch:
- Brake Lights Don't Work: The most common and dangerous symptom. If the switch fails in the open position, it will never complete the circuit to turn your brake lights on.
- Brake Lights Stay On: If the switch gets stuck in the closed position, your brake lights will remain on even when your foot is off the pedal. This will drain your battery and confuse drivers behind you.
- Intermittent Brake Lights: The lights may flicker or only work sometimes when you press the pedal. This points to a worn-out switch with an inconsistent internal connection.
Safety First
Driving without functional brake lights is illegal and extremely dangerous. If you suspect your brake light switch has failed, you should confirm the issue and replace the part immediately. It is not safe to drive the vehicle if the brake lights do not illuminate when you press the pedal.
Choosing the Right Aftermarket Brake Light Switch
For a vintage truck like the 1975-1978 C35, original equipment (OEM) parts from GM are likely discontinued or very difficult to find. Fortunately, the aftermarket offers reliable and affordable replacements. The design of this switch is simple, and quality aftermarket versions are more than adequate for keeping your classic on the road safely.
Available Brand Tiers:
- Standard Ignition (Good): Standard Motor Products (SMP) is a well-known and trusted name in the aftermarket industry with a long history. Their switches are known for being reliable, fitting correctly, and performing like the original part. For a critical safety component, choosing a reputable brand like Standard is a solid investment.
- Skyward (Economy): Skyward is a more budget-friendly option. While there is less brand history and fewer public reviews available for this specific part, it can be a viable choice for owners on a tight budget. The Better Business Bureau gives the company a B- rating, noting a failure to respond to one complaint.
Pro Tip: Check for Cruise Control
Some replacement switches are specifically noted as being for models "Without Cruise Control." While cruise control was not a common option on these work trucks, ensure you select the correct part for your vehicle's configuration to guarantee a proper fit and function.
Brake Light Switch Replacement Cost
Replacing the brake light switch is one of the more affordable repairs you can perform on your truck. The parts are inexpensive, and if you do it yourself, the only cost is the part itself. Even having a shop do the work is relatively cheap due to the low labor time required.
| Cost Category | Estimated Price Range |
|---|---|
| New Aftermarket Part | $5.40 - $29.97 |
| Shop Labor | $50 - $100 |
| DIY Total Cost | $5.40 - $29.97 |
| Shop Total Cost | $55 - $130 |
Frequently Asked Questions
Where is the brake light switch located on my 1975-1978 GMC C35?
The brake light switch is mounted to the brake pedal support bracket, located under the driver's side of the dashboard. You will need to look up above the brake pedal arm to see it. It's a small switch with a wiring connector plugged into it.
Is replacing the brake light switch a difficult job?
No, this is a very feasible DIY job for most owners. It typically requires only basic hand tools and can be completed in under 30 minutes. The most difficult part is often the uncomfortable position of working under the dashboard.
My brake lights are stuck on. Do I need a new switch?
Most likely, yes. When brake lights stay on, it usually means the switch has failed in the closed or "on" position. Before replacing it, quickly check that the brake pedal is not stuck and is returning to its normal resting position. If the pedal is fine, the switch is the probable cause.
Can I adjust the brake light switch?
Some switches on these older trucks can be adjusted by changing their position on the bracket to ensure the pedal plunger makes proper contact. However, if the switch is failing internally (sticking on/off or working intermittently), adjustment will not fix the problem, and replacement is the only solution.
Technical Specifications
OEM Part Numbers: 358560C1
2-Terminal, Push-type switch, mounts on brake pedal bracket.
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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.