Mercury Comet Brake Light Switch Guide: 1966-1970
Keep your classic Comet safe and visible by understanding, diagnosing, and replacing this critical part.
- A failing brake light switch is a critical safety issue and must be addressed immediately.
- The two main symptoms are brake lights that don't work at all or brake lights that stay on constantly.
- Replacement is a simple, DIY-friendly job that takes less than an hour.
- Choose a quality aftermarket brand like Standard Ignition or Rostra to ensure reliability.
Is Your Comet's Brake Light Switch Failing?
A faulty brake light switch on a classic car like the Mercury Comet is a major safety hazard. Unlike modern cars with complex electronics, the signs of failure on a 1966-1970 Comet are straightforward. The switch typically fails in one of two ways: either stuck 'on' or stuck 'off'.
Key Failure Symptoms
- Brake Lights Do Not Turn On: This is the most dangerous symptom. You press the brake pedal, but the lights don't illuminate, making you invisible to drivers behind you when you slow down. This can be caused by an internal failure of the switch.
- Brake Lights Stay On: The switch can also fail in the closed position, causing the brake lights to remain on even when you're not braking. This can confuse other drivers, drain your battery, and cause the bulbs to burn out prematurely.
Choosing the Right Aftermarket Switch
For a vehicle from this era, finding a "New Old Stock" (NOS) OEM Ford part is rare and often expensive. The most practical and common solution is a new aftermarket switch. Aftermarket parts from reputable brands are widely available and can be more reliable than the 50-year-old original design.
Two common brands you will find are Standard Ignition (SMP) and Rostra Powertrain.
- Standard Ignition: A well-known name in the aftermarket, Standard Ignition produces a wide range of replacement parts. Their switches are generally considered a reliable, quality replacement for classic vehicles.
- Rostra Powertrain: Rostra specializes in vehicle electronics for both aftermarket and original equipment applications. They state their parts are engineered to meet or exceed original specifications and are 100% tested for reliability.
Pro Tip: While tempting to buy the cheapest switch available, low-quality switches are known to fail prematurely. Investing in a recognized brand like Standard Ignition or Rostra is a small price to pay for safety and reliability.
Cost to Replace a Mercury Comet Brake Light Switch
| Part/Service | Estimated Cost |
|---|---|
| New Aftermarket Switch | $16 - $26 |
| Shop Labor | $50 - $100 |
| Total Estimated Cost | $66 - $126 |
Costs are estimates and may vary based on your location and the specific repair shop. This is a very simple job for a DIYer.
Frequently Asked Questions
Can I replace the brake light switch myself?
Yes, this is a great DIY task for any skill level. The switch is located under the dashboard, attached to the brake pedal assembly. The job typically requires no special tools—just the ability to work in a slightly awkward position. You will need to disconnect the wiring harness and remove a small clip or bolt to swap the old switch for the new one.
How do I know for sure the switch is the problem?
First, check the bulbs and the fuse. If those are good, the switch is the next logical culprit. If the lights are stuck on, you can try unplugging the switch; if the lights turn off, the switch is bad. If the lights don't work at all, you can use a multimeter to test for continuity across the switch's terminals when the pedal is pressed.
Is it safe to drive with a bad brake light switch?
No. Driving without functioning brake lights is extremely dangerous and illegal. It dramatically increases your risk of being rear-ended. If you suspect your brake light switch has failed, you should not drive the vehicle until it is repaired.
Is there a difference between switches for manual and power brakes?
While the fitment is generally the same, some aftermarket manufacturers offer different parts for manual and power brake applications. The primary difference is often the internal spring stiffness, designed to match the pedal feel. For a 1966-1970 Comet, the part is largely interchangeable with other Fords like the Falcon and Fairlane. Always verify the part fits your specific year and model. The OE reference number is C9OZ-13480-A.
Technical Specifications
OEM Part Numbers: C9OZ-13480-A
A 2-terminal, mechanical switch activated by the brake pedal arm, mounted under the dashboard.
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.