1985-1986 Ford Mustang Tail Lamp: GT, SVO, and 1993 Cobra Differences

Key Differences and Interchangeability: GT/LX vs. SVO vs. 1993 Cobra

One of the most confusing aspects of 1985-1986 Mustang tail lamps is the variation between trim levels and the interchange with other model years. Getting the right lamp is crucial for a correct restoration.

1985-1986 Mustang GT and LX

The standard tail lamp for GT and LX models features a smooth lens with a distinctive charcoal gray outer trim. This style replaced the black trim used on 1983-1984 models. These lamps are a direct fit for 1983-1986 Mustangs.

1985-1986 Mustang SVO

The high-performance SVO model was equipped with a unique tail lamp to differentiate its styling. These lenses feature thin, horizontal charcoal-colored stripes or lines across the entire surface, giving them a louvered appearance. This style is often nicknamed "cheese grater" lights, though that term is more commonly associated with 1987-93 GT models.

The 1993 Cobra Connection

Fitment on Other Fox Body Mustangs (1983-1993)

All Fox Body tail lamp lenses from 1983 to 1993 are physically interchangeable, meaning they will bolt into place. However, there are cosmetic differences:

• On a 1983-1984 Mustang: The 1985-1986 GT/LX lamps are a direct swap and popular styling upgrade, with the only difference being the trim color (gray vs. the original black).
• On a 1987-1993 Mustang: While 1985-1986 lenses will fit, they will be recessed into the body opening by about half an inch, as the later 'Aero' cars had slightly deeper lamp assemblies. This may not be aesthetically pleasing for all owners.

Symptoms of Failure

Tail lamp issues on the 1985-1986 Mustang are typically related to age, environmental exposure, and electrical connections rather than a specific design flaw.

• Condensation or Water Inside the Lens: Fogging or visible water droplets inside the housing are the most common problem. This is caused by a failed seal between the lens and the housing. If left unaddressed, the moisture will corrode bulb sockets and wiring, leading to intermittent or dead lights.
• Dim or Non-Functioning Lights: This can be as simple as a burnt-out bulb. However, it can also point to corrosion on the bulb socket contacts or a bad ground connection. Over time, the reflective chrome paint inside the housing can flake off, reducing brightness.
• Cracked or Faded Lens: Decades of UV exposure from the sun can make the plastic lens brittle, hazy, and prone to cracking. This not only looks bad but can also allow water to enter.
• Flickering Lights: Lights that flicker, especially when going over bumps, often indicate a loose bulb, a corroded socket, or a failing electrical connector or ground wire.

Buying a Used Tail Lamp: What to Check

Given the age of these vehicles, a quality used OEM tail lamp is often the best choice for fit and originality. Aftermarket parts can suffer from poor fitment, premature fading, and seals that leak. When inspecting a used part, look for the following:

1. Check for the Ford Logo: Genuine OEM parts will have a Ford logo and part number molded into the plastic of the lens and/or housing. This is the best way to ensure you're getting an original part with factory-grade quality.
2. Inspect the Lens Thoroughly: Hold the lens up to the light. Look for hairline cracks, especially around the edges and mounting points. Check for hazing, yellowing, or deep scratches that can't be polished out.
3. Examine the Housing: Check the black plastic housing for any cracks, particularly around the mounting studs. Ensure the studs are intact and not stripped.
4. Look for Signs of Water Intrusion: Check inside the housing for a "water line," mineral deposits, or rust on any metal components. This indicates the seal has failed and the unit may have hidden electrical corrosion.
5. Inspect the Bulb Sockets: Look at the metal contacts inside the bulb sockets. They should be clean and shiny. Avoid any assembly with green or white corrosion, or melted plastic around the socket.
6. Verify the Style: Double-check whether you are buying the smooth GT/LX style or the striped SVO/Cobra style to ensure it matches your vehicle's trim.

Cost Comparison

Prices can vary based on condition and availability, especially for New Old Stock (NOS) parts.

Replacement and Repair

Replacing the tail lamp assembly is a straightforward job suitable for any DIY mechanic.

• Difficulty: 1 out of 5
• Estimated Time: 0.5 hours
• Tools Needed: Deep well socket set (typically 11mm)

The assembly is held in place by several nuts accessible from inside the trunk. Simply remove the trunk liner panel, unplug the single wiring harness connector, and undo the nuts. The entire assembly will then pull out from the rear of the car. Installation is the reverse of removal.

How to Fix a Leaking Tail Lamp

If your lamp has condensation but is otherwise in good shape, you can often reseal it.

1. Remove the tail lamp assembly from the vehicle.
2. Carefully remove the bulbs and let the housing air out in a warm, dry place (like in the sun) for several hours until all moisture has evaporated. A hair dryer on a low setting can speed this up.
3. Once dry, apply a thin, continuous bead of clear automotive-grade silicone sealant around the entire seam where the lens meets the black housing.
4. Allow the sealant to cure completely according to the manufacturer's instructions before reinstalling the lamp.

Frequently Asked Questions (FAQ)

Recalls and Technical Service Bulletins (TSBs)

As of this writing, there are no specific NHTSA recalls or TSBs related to the tail lamp assemblies for the 1985-1986 Ford Mustang. Any issues are typically due to age-related wear and tear.