Guide to the 1967-1974 GMC C35/C3500 Pickup Headlight Switch
Don't get left in the dark; understand the headlight switch in your classic GMC truck.
- A failing headlight switch is a critical safety issue; replace it immediately if lights flicker or cut out.
- Symptoms include non-working lights, flickering, and loss of dash light control.
- Replacement is a straightforward DIY job, mainly requiring work under the dash.
- Verify the pin count (7-pin vs 8-pin) on your original switch before ordering, as it changed during these years.
Signs of a Failing Headlight Switch
A bad headlight switch on a vintage truck will give you clear warning signs. Because it controls multiple lighting systems, a failure can show up in several ways.
Common Failure Symptoms
- Headlights or Parking Lights Don't Turn On: The most obvious sign is when your lights fail to illuminate at all. This could be a complete failure of the switch.
- Lights Flicker or Cut Out: If your headlights flash on and off while driving, it could be the internal circuit breaker in the switch cycling due to corrosion, high resistance, or a short circuit.
- Dash Lights Don't Work or Won't Dim: The part of the switch that controls the instrument panel lights (a rheostat) can fail, leaving you with no dash lights or an inability to adjust their brightness.
- Switch Feels Hot: A failing switch with high internal resistance can get warm or hot to the touch. This is a serious sign that replacement is needed immediately.
- Melted Wires: In severe cases, a faulty switch or a short in the wiring can cause enough heat to melt the plastic connector and wires at the back of the switch.
Choosing Your Aftermarket Headlight Switch
For a truck of this era, OEM parts are long gone. Aftermarket is your only real option for a new switch. The good news is that aftermarket brands have been making these switches for decades. Quality is generally good, but it's worth knowing the difference between the available brands.
Brand Tiers
- Standard Ignition: Often considered a top-tier aftermarket brand, Standard Motor Products has been around for over 100 years. They manufacture a wide range of electrical components and are known for quality control, often testing parts to meet or exceed original specifications. For a critical component like a headlight switch, Standard is a trusted choice.
- Replacement: This is a generic or house brand. Quality can be a mixed bag, but for a common part like a GM headlight switch, they are often perfectly functional and offer a good value. They are designed as direct-fit replacements and are a cost-effective way to get your lights working again.
Year-Specific Switches
Be aware that not all switches from 1967-1972 are the same. For example, 1967 trucks used an 8-pin switch, while 1968-1972 models used a 7-pin switch. The 8-pin switch in 1967 models turned the parking lights off when the headlights were on. Always verify the pin count on your old switch before ordering a new one to ensure you get the correct part.
Cost of a New Headlight Switch (1967-1974 GMC C35/C3500)
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Replacement, Standard Ignition) | $27.74 - $58.42 |
| Shop Labor | $60 - $120 |
Frequently Asked Questions (FAQ)
Is it difficult to replace the headlight switch myself?
No, it's a relatively easy job for a DIY mechanic. The main challenge is access, as you have to work under the dashboard. The process involves disconnecting the battery, removing the knob and shaft, unscrewing a retaining nut, and unplugging the switch from the wiring harness. The knob is released by pressing a small spring-loaded button on the switch body itself.
Do I need any special tools?
No special tools are required. A set of screwdrivers and possibly some needle-nose pliers to loosen the bezel nut are usually all that's needed. Having a multimeter to test for power can also be helpful for diagnosis.
My headlights work but my high beams don't. Is that the switch?
It could be, but it's more likely the floor-mounted dimmer switch. Power for both high and low beams runs through the dimmer switch after leaving the main headlight switch. If the dimmer switch fails, it can prevent either the low beams or high beams (or both) from working. Always check the dimmer switch as a possible cause for high beam problems.
Are there any recalls for the headlight switch on these trucks?
There are no specific recalls found for the headlight switch on the 1967-1974 GMC C35/C3500 Pickup. Any issues you encounter are due to the age and normal wear of the original components.
Technical Specifications
Pull-style switch with rotating knob for instrument dimmer. Features an internal, self-resetting circuit breaker. Pin configuration varies by year (e.g., 8-pin for 1967, 7-pin for 1968-72).
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.