GMC R3500 Back Up Light Switch Guide for 1987-1991 Models
Solve your reverse light problems by choosing the right switch for your R3500's transmission.
- The most critical step is to order the correct switch for your transmission type (automatic or manual), as they are different parts in different locations.
- Common symptoms include reverse lights not working, staying on, or flickering.
- On automatic models, a faulty switch can also cause a no-start condition.
- Before replacing the switch, always check the bulbs and the fuse first to rule out simpler problems.
Is Your R3500 Back Up Light Switch Failing?
On a workhorse truck like the 1987-1991 GMC R3500, electrical components are exposed to years of use and can wear out. A faulty back up light switch is a common issue, but the symptoms are usually clear, making it easy to diagnose.
Key Failure Symptoms
- Reverse Lights Don't Turn On: This is the most common and dangerous symptom. If you've already checked the bulbs and the fuse (often labeled "TURN B/U"), the switch is the most likely cause.
- Reverse Lights Stay On: The switch can get stuck in the 'on' position, leaving your reverse lights on constantly. This can drain your battery and confuse other drivers.
- Flickering or Intermittent Lights: You may find the lights only work when you jiggle the column shifter. This points to a worn-out or misaligned switch.
- Engine Won't Start (Automatic Only): Since the switch is often combined with the neutral safety switch, a failure can prevent the engine from starting, or it may only start in Park but not Neutral (or vice-versa).
A Critical Ordering Mistake to Avoid
The single most important factor when ordering this part is your truck's transmission type. The switch for an automatic transmission is completely different from the one for a manual transmission.
- Automatic Transmission: The switch is located on the steering column, inside the cab under the dashboard. It's a larger, crescent-shaped plastic part that also functions as the neutral safety switch.
- Manual Transmission: The switch is a small, threaded sensor located on the side of the transmission case itself.
Always confirm your transmission type before purchasing to avoid getting the wrong part.
Choosing the Right Aftermarket Switch
For a vehicle of this age, original OEM parts are generally unavailable. Aftermarket parts are the go-to solution and offer reliable performance.
Brand Tiers:
- Standard Ignition: A well-regarded aftermarket brand known for producing parts that meet or exceed original specifications. For a critical safety and starting component, Standard Ignition is a trusted choice that often fits and functions like the original part.
- Replacement: These are value-focused brands that provide a functional part at a lower cost. For a simple switch, this can be a perfectly adequate and budget-friendly option.
Pro Tip: Before replacing the switch, always check the simple things first. Make sure your reverse light bulbs are good and check the fuse in the fuse panel. This can save you time and money.
Cost of Replacing a Back Up Light Switch (1987-1991 GMC R3500)
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket Switch | $26.16 - $31.75 |
| Shop Labor | $60 - $120 |
Frequently Asked Questions (FAQ)
Where is the back up light switch located on my R3500?
For 1987-1991 models with an automatic transmission, the switch is mounted on the steering column, under the dash inside the cab. For trucks with a manual transmission, it is a smaller switch screwed into the side of the transmission housing.
Is this a difficult part to replace myself?
For most DIY mechanics, this is a feasible job. On automatic models, the main challenge is the awkward access under the dashboard, but it typically clips into place without special tools. For manual transmission models, you will need to safely lift the vehicle on jack stands to access the switch on the transmission. The difficulty is low to moderate.
My reverse lights flicker. Can I just adjust the switch?
Yes, on automatic models, the column-mounted switch is adjustable. You can try loosening its mounting screws and rotating it slightly to see if that restores consistent operation when shifting into reverse. If the internal contacts are worn, however, replacement is the only permanent fix.
Are there any recalls for this part?
No. Searches of the National Highway Traffic Safety Administration (NHTSA) database show no recalls specifically for the back up light switch or neutral safety switch on the 1987-1991 GMC R3500.
Technical Specifications
OEM Part Numbers: 14014559 15566155 93439332
Varies by transmission type. Automatic transmission switch is a multi-function switch (backup lights and neutral safety) mounted on the steering column. Manual transmission switch is a 2-terminal switch mounted 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.
- GMC R3500: