GMC K3500 Back Up Light Switch Guide for 1979-1987 Models
Fixing your reverse lights is a simple but critical job for the safety and legality of your classic GMC truck.
- The correct switch is different for automatic and manual transmissions; this is the most important detail when ordering.
- For automatic models, the switch is on the steering column; for manual models, it's on the transmission case.
- Symptoms include no reverse lights, lights stuck on, or flickering lights.
- Always check bulbs, the fuse, and wiring grounds before replacing the switch.
Is Your Back Up Light Switch Failing?
A bad back up light switch is more than an inconvenience; it's a safety issue that could get you a ticket. Luckily, the signs of failure are usually easy to spot. Before you replace the switch, it's always a good idea to check the simple things first: make sure the fuse (often labeled "B/U Lamps") and the bulbs themselves are good. A common issue on these older trucks is also bad grounds or corroded bulb sockets, so check those too.
Symptoms of a Bad Back Up Light Switch
- No Reverse Lights: The most common symptom. After confirming the bulbs and fuse are okay, the switch is the next likely culprit. You can test this by using a jumper wire on the switch's connector; if the lights come on, the switch is bad.
- Reverse Lights Stay On: If the switch is stuck in the 'on' position, your back up lights won't turn off. This can confuse other drivers and drain your battery.
- Flickering or Intermittent Lights: Lights that only work when you wiggle the shifter often point to a worn-out or misadjusted switch. For automatic models, the switch on the steering column may just need a simple adjustment.
Choosing the Right Aftermarket Switch
For a classic truck like the '79-'87 K3500, original OEM parts are scarce and often discontinued. The good news is that the aftermarket offers reliable and affordable replacements. The most critical factor is buying the correct switch for your transmission type, as the parts for automatic and manual transmissions are completely different.
- Standard Ignition: A well-known and widely available brand that is generally considered a reliable choice for replacement electrical parts like these. They offer switches for both manual and automatic applications for this truck series.
- Rostra Powertrain: Rostra specializes in transmission components and is an OE-certified manufacturer for some brands. They are a solid choice, providing quality parts that are built to meet or exceed original standards.
Pro Tip: When ordering, double-check if your truck is an automatic or a manual. An automatic uses a switch on the steering column, while a manual has a switch on the transmission case itself. This is the most common ordering mistake.
Cost to Replace a GMC K3500 Back Up Light Switch
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Standard, Rostra) | $16 - $27 |
| New OEM | Very limited availability, likely $40+ if found |
| Shop Labor | $50 - $125 |
Frequently Asked Questions (FAQ)
Where is the back up light switch on my K3500?
It depends on your transmission. For automatic transmissions, it's part of the neutral safety switch, located at the base of the steering column inside the cab, near the firewall. For manual transmissions, it's a screw-in switch on the transmission itself, often on the top or side.
Can I replace this switch myself?
Yes, this is a great DIY job for most owners with basic tools. The difficulty is low. For a manual, you'll need to safely get under the truck to access the transmission. For an automatic, you'll work under the dashboard. In some 4x4 manual trucks, you can access the switch from inside the cab by removing the transmission floor cover.
Do I need to adjust the new switch?
For manual transmissions, no adjustment is needed; you just screw it in. For automatic transmissions, the switch on the steering column may need to be adjusted. You can do this by loosening its mounting screws and rotating it slightly until the reverse lights come on only when the shifter is in the reverse position.
My lights still don't work after replacing the switch. Now what?
If a new switch, fuse, and bulbs don't solve the problem, you likely have a wiring issue. Check for power at the switch connector with a test light. Trace the wiring for any breaks, corrosion, or bad grounds, paying close attention to the connectors and the sockets at the tail lights.
Technical Specifications
OEM Part Numbers: 14014559 14014555
Varies by transmission type. Automatic transmission switches are integrated with the neutral safety switch on the steering column. Manual transmission switches are typically 2-terminal, screw-in plunger-style switches located on the transmission housing.
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.