GMC K35/K3500 Pickup Ignition Switch: A Complete Guide for 1968-1974
Don't get stranded by a faulty ignition switch; here’s what you need to know for your classic GMC heavy-duty pickup.
- First, confirm your truck's year to determine if you have a dash-mounted (1968-72) or column-mounted (1973-74) switch, as the parts and labor are different.
- Symptoms like 'no-start' or stalling are critical. A failing switch can leave you stranded or cause a dangerous situation on the road.
- Choose a quality aftermarket brand like Standard Ignition or Rostra for reliability; cheap, unbranded switches are known to fail prematurely.
- Always inspect the wiring connector for melting or damage when replacing the switch. A bad connector will ruin the new part.
Is Your GMC K35/K3500 Ignition Switch Failing?
A bad ignition switch in these classic GMC trucks can cause frustrating problems that might seem like a dead battery or bad carburetor. Because the switch controls power to so many components, its failure can lead to a no-start situation or dangerous stalling while driving. Recognizing the signs early can save you from a major headache.
Common Symptoms of a Bad Ignition Switch:
- Truck Won't Start or Crank: You turn the key and nothing happens, or you only hear a single click. Power isn't reaching the starter.
- Intermittent Stalling: The engine shuts off unexpectedly while you're driving, especially when hitting a bump or wiggling the key. This happens when the switch's internal contacts are worn and briefly lose connection.
- Accessories Don't Work: Your radio, heater fan, or wipers won't turn on, or they cut out intermittently. The switch isn't sending power to the accessory circuits.
- Key is Hard to Turn: The mechanical parts of the switch or the lock cylinder it connects to may be binding or worn out.
- Visible Smoke or Melting: You might see or smell smoke from the dashboard or steering column area. A close look at the switch may reveal melted plastic or burnt wires, often caused by age or improperly installed high-draw accessories.
A Critical Note for 1973-1974 Owners
GMC changed the location of the ignition switch during this period. It is crucial to know your truck's year before buying parts or starting a repair.
- 1968-1972 Models: The ignition switch is mounted directly on the dashboard.
- 1973-1974 Models: The ignition switch was moved to the top of the steering column, located further down under the dash.
This guide covers both, but be aware that the replacement process is different for each style.
Choosing the Right Aftermarket Ignition Switch
For a vintage truck like the K35/K3500, original OEM parts are virtually nonexistent. The aftermarket is your primary source. Quality here is key, as a cheap switch can fail quickly or even be a fire hazard.
Brand Quality Tiers
- Premium Aftermarket (Standard Ignition, Rostra Powertrain): Brands like Standard Ignition (also known as SMP) are highly recommended on forums and by technicians for their durability and use of quality materials like copper conductors. Rostra is a known OE manufacturer with quality certifications, ensuring their parts meet high standards. These brands are your best bet for long-term reliability.
- Value-Priced Aftermarket (Replacement): This category includes generic or store-brand parts. While the price is attractive, the quality can be inconsistent. These switches may use cheaper materials that wear out faster or have poor fitment, leading to installation problems. They are a viable option for a tight budget, but inspect the part carefully before installation.
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket | $20.77 - $55.28 |
| Shop Labor | $75 - $250 |
Note: Labor costs vary significantly based on whether you have a dash-mounted (1968-72) or column-mounted (1973-74) switch, with the column-mounted version being more labor-intensive.
Pro Tip: Check Your Wiring
When you replace your ignition switch, inspect the wiring connector (pigtail) for any signs of melting, corrosion, or damage. A bad connector can destroy a new switch. If it looks burnt, replace it at the same time.
Frequently Asked Questions (FAQ)
Can I replace the ignition switch myself?
Yes, this is a DIY-friendly job for most home mechanics. For 1968-1972 dash-mounted switches, the job is simpler and requires basic hand tools, a paperclip to release the lock cylinder, and possibly a special bezel nut tool. For 1973-1974 column-mounted switches, the job is more involved and requires lowering the steering column for access, but is still manageable.
How do I know if I have a dash-mounted or column-mounted switch?
Look at where you insert your key. If the key goes directly into the dashboard, you have a dash-mounted switch (common for 1968-1972 models). If the key goes into the steering column, the switch itself is a separate component attached to the top of that column under the dash (common for 1973-1974 models).
What happens if I don't replace a bad ignition switch?
Ignoring a failing ignition switch can leave you stranded without warning. The most serious risk is the engine stalling in traffic, which causes a loss of power steering and can be very dangerous. There is also a fire risk if the switch or its wiring overheats and melts.
Do I need to replace my keys and door locks too?
Not usually. Most ignition switches are sold separately from the lock cylinder (the part your key goes into). You can typically remove your existing lock cylinder and install it in the new switch, allowing you to keep your original keys.
Technical Specifications
OEM Part Numbers: 1116683 1116695 1116704 1116709 1116711 1116712
Varies by year. 1968-1972 models use a dash-mounted switch assembly. 1973-1974 models use a steering column-mounted switch actuated by a rod connected to the lock cylinder.
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.