GMC C1500 Back Up Light Switch Guide for 1979-1987 Models
If your reverse lights are out, the problem is often a simple switch you can replace yourself.
- First, confirm if your truck has an automatic or manual transmission to buy the correct switch.
- On automatic models, try adjusting the switch on the steering column before replacing it; it may have just slipped out of position.
- Always check the bulbs and the 'TURN B/U' fuse before assuming the switch is bad.
- Replacement is a simple, DIY-friendly job that can usually be done in under an hour with basic tools.
Symptoms of a Failing Back Up Light Switch
When a back up light switch starts to fail on your GMC C1500, the signs are usually obvious. The most common issue is that the reverse lights do not turn on at all when you shift into reverse. You might also experience flickering or intermittent lights, where they work one moment and not the next. Some owners report having to wiggle the column shifter to get the lights to activate, which points to a worn or misaligned switch. In some cases, a short circuit within the switch can repeatedly blow the fuse labeled "TURN B/U".
Check the Simple Stuff First
Before replacing the switch, always check for burned-out bulbs, corrosion in the light sockets, and the "TURN B/U" fuse. Also, inspect the wiring for obvious damage. These simple checks can save you time and money.
Choosing the Right Aftermarket Back Up Light Switch
For a classic truck like the 1979-1987 C1500, the aftermarket is the most common source for replacement parts like the back up light switch. Original GM parts may be difficult to find or discontinued. Fortunately, aftermarket brands offer reliable and affordable solutions.
The most important factor is buying the correct switch for your transmission type:
- Automatic Transmission: You need the crescent-shaped Neutral Safety / Back Up Light Switch that mounts to the steering column under the dashboard.
- Manual Transmission: You need the plunger-style switch that threads into the transmission case.
Available Aftermarket Brands
Two common brands you will find are Standard Ignition and Rostra Powertrain.
- Standard Ignition (SMP): This is a very well-known and widely available aftermarket brand. They are generally considered a reliable choice for common replacement parts and are frequently used by both DIYers and professional shops.
- Rostra Powertrain: Rostra is also a known name in the parts industry, particularly for transmission components. They provide a viable alternative for your C1500.
For a simple and affordable part like this, both brands should provide a functional replacement. The quality of aftermarket parts can sometimes be inconsistent, with some forum users noting that new switches may require frequent readjustment. However, for most owners, a new aftermarket switch is an effective and long-lasting repair.
Estimated Cost for Back Up Light Switch Replacement
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Switch | $16.17 - $26.63 |
| Shop Labor | $50 - $100 |
A Note on Adjustment
For automatic transmission models, the switch on the steering column is adjustable. Sometimes, the reverse lights fail simply because the switch has slipped out of alignment. It can be adjusted by carefully rotating it on the column until the lights work correctly when in reverse. If adjustment doesn't solve the problem, a replacement is needed.
Frequently Asked Questions (FAQ)
Where is the back up light switch on my C1500?
If you have an automatic transmission, the switch is a crescent-shaped plastic part attached to the base of the steering column, inside the cab near the firewall. If you have a manual transmission, the switch is located on the side of the transmission itself.
Can I replace the back up light switch myself?
Yes, this is a very DIY-friendly job. For automatic models, access is under the dashboard. For manual models, you will need to safely get under the truck to access the transmission. The difficulty is low, typically taking less than an hour.
Do I need any special tools to replace the switch?
No special tools are usually required. Basic hand tools like a socket set and screwdrivers are typically sufficient. For the switch on a manual transmission, you may need a wrench or a deep socket to unscrew it.
My reverse lights still don't work after replacing the switch. What now?
If a new switch doesn't fix the problem, the issue is elsewhere in the circuit. Check the bulbs again, and inspect the bulb sockets for corrosion. Use a test light to check for power at the switch connector and at the tail light sockets to trace where the power is being lost. The problem could be a broken wire or a bad ground.
Technical Specifications
OEM Part Numbers: 15566155
Location and type vary by transmission. Automatic transmissions use a crescent-shaped switch on the steering column. Manual transmissions use a plunger-style switch on the transmission case.
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.