1974-1979 GMC Jimmy HVAC Blower Control Switch Replacement Guide
Restore all fan speeds for your Jimmy's heating and air conditioning with a new blower control switch.
- For a 1974-1979 Jimmy, a new aftermarket switch is the most practical and available option.
- The most common symptom of failure is the fan only working on the 'High' setting.
- Always inspect the blower motor and resistor wiring for damage when replacing the switch to prevent a repeat failure.
- You must order the correct part based on whether your truck has factory A/C or is heater-only.
Symptoms of a Failing Blower Control Switch
On a classic truck like the 1974-1979 GMC Jimmy, the climate control system is simple, and the signs of a bad blower switch are usually clear. You will likely notice one of the following issues:
- Fan Only Works on High: This is a very common symptom. While it's often caused by a failed blower motor resistor, it can also mean the switch itself is bad and no longer sending power to the resistor for the lower speeds.
- No Fan on Any Speed: If the fan doesn't turn on at all, the switch may have failed completely. Other causes could be a blown fuse or a dead blower motor, so further diagnosis is needed.
- Intermittent Operation: You might have to jiggle the switch lever to get the fan to work. This points to worn internal contacts in the switch or a loose wire connector on the back.
- Melted Connector or Burning Smell: A smell of burning plastic from the dash is a serious sign. It often means an old, failing blower motor is drawing too much electricity, causing the switch and its wiring to overheat and melt.
Check Related Parts First
A bad blower switch can be a symptom of another issue. An old blower motor that is hard to spin will draw too much electrical current and can melt a brand-new switch. Before installing a new switch, inspect the blower motor resistor and its wiring for melting or corrosion. Also, try to spin the blower motor fan by hand. If it feels stiff or makes noise, it should be replaced at the same time to prevent the new switch from failing prematurely.
Choosing the Right Aftermarket Switch
For a vehicle from the 1970s, finding new original equipment manufacturer (OEM) parts is nearly impossible. The most practical and reliable choice is a new aftermarket part. Used OEM switches from a junkyard are an option, but they are just as old as the part you are replacing and may fail soon.
Four Seasons is a well-known aftermarket brand that manufactures a wide range of climate control parts. They are a major supplier in the industry, and their parts are generally considered a reliable and cost-effective solution for keeping a classic Jimmy's HVAC system running. When ordering, you must get the correct switch based on whether your Jimmy has factory Air Conditioning (A/C) or is a heater-only model, as the switches are different.
Cost of a New HVAC Blower Control Switch (1974-1979 GMC Jimmy)
| Part Type | Estimated Cost |
|---|---|
| New Aftermarket (Four Seasons) | $54.66 |
| New OEM | Not Available |
| Used OEM | $20 - $50 (High Risk) |
| Shop Labor | $100 - $150 |
DIY Installation Tip
Replacing the blower control switch is a straightforward job for a DIYer. The switch is located within the heater control panel on the dashboard. You will need to carefully remove the dash bezel, unscrew the control unit, and swap the switch. A video guide for a similar GM truck shows the process involves removing one screw with a 1/4" socket to release the switch from the control assembly. Be gentle, as the old plastic dash parts can be brittle.
🎬 See a step-by-step video on replacing the blower switch.Frequently Asked Questions
Why does my fan only work on the 'High' setting?
This usually happens because the blower motor resistor has failed. The 'High' setting bypasses the resistor, which is why it's the only speed that works. 🎬 Watch this guide on diagnosing fan speed issues and failures. However, a bad switch or a faulty blower motor relay can also cause this issue.
Is the blower switch the same as the blower motor resistor?
No. The blower switch is the control on your dash you move with your hand. The blower motor resistor is a separate part, usually located under the hood on the passenger side firewall, that the switch sends power through to create the lower fan speeds.
Are there any recalls for the blower switch on my GMC Jimmy?
No, there are no specific recalls or Technical Service Bulletins (TSBs) from the National Highway Traffic Safety Administration (NHTSA) for the HVAC blower control switch on the 1974-1979 GMC Jimmy. Searches found recalls for newer GM models with different issues, but none apply to this generation.
Do I need the switch for A/C or non-A/C?
You must order the switch that matches how your Jimmy was built from the factory. Even if your A/C system no longer works, if the truck originally came with it, you need the switch designed for A/C models. The two versions are different and are not interchangeable.
Helpful Videos
Technical Specifications
OEM Part Numbers: 370809 469368
Dash-mounted 3 or 4-speed fan selector switch. The specific switch (and number of terminals) depends on whether the vehicle was equipped with factory air conditioning.
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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.