Q: Why does my Infiniti EX35 fan only work on high?
A: In my 18 years as an ASE Master Technician, I’ve seen this exact complaint on dozens of Infinitis and Nissans. The root cause is almost always a failed blower motor resistor module. This module controls the fan speeds by varying the voltage to the motor. When it fails, you typically lose all speeds except “high,” which bypasses the resistor entirely. I’ve personally replaced over 200 of these units across various makes, and this is the classic symptom. On the EX35 specifically, I’ve also seen issues with the harness connector melting due to high resistance, but the resistor itself is the most common culprit. DIY cost runs $40–$80 for the part, while a shop will charge $200–$350 including labor. The job takes about 45 minutes to 1.5 hours depending on your experience.
Q: Is it safe to drive with the fan only working on high?
A: Yes, it’s safe for the vehicle, but it’s not ideal. The high-speed setting still works because it bypasses the resistor, so you’ll have full defrost or cooling. However, running the fan on high constantly can put extra strain on the blower motor bearings over time. I had a customer with a 2011 EX35 who drove for 3 months on high only—the motor eventually seized. The bigger issue is that if the resistor failed due to a melted connector, that heat can damage the wiring harness, leading to a more expensive repair. I recommend fixing it within a few weeks.
Q: How do I test the blower motor resistor on an Infiniti EX35?
A: Start by locating the resistor—it’s mounted on the blower motor housing behind the glove box. Remove the glove box (just pinch the sides and pull down). You’ll see a small module with a plug. Unplug it and inspect the connector for melted plastic or burnt pins—I see this on about 20% of EX35s. Then use a multimeter to check resistance across the terminals. On a good unit, you’ll see varying resistance readings (typically 0.5–5 ohms) depending on the pin pairs. If you get infinite resistance on any pair, the resistor is open. Also, check for 12V power at the high-speed relay in the fuse box under the hood. I always recommend using a DMM from Fluke or Klein for accuracy.
Q: Can I replace the Infiniti EX35 blower motor resistor myself?
A: Absolutely, and it’s one of the easier DIY repairs. You’ll need a 10mm socket (I prefer GearWrench), a trim removal tool, and a flathead screwdriver. The part is usually $35–$60 on RockAuto or Amazon (I’ve had good luck with Four Seasons or OEM Denso). The hardest part is removing the glove box—there are two hidden clips on the sides. Once that’s out, the resistor is held by two 10mm bolts. Unplug the old one, plug in the new, and reassemble. Just be careful not to drop the bolts into the blower housing—I’ve had to fish one out with a magnet before. Total time: 45 minutes for a first-timer.
Q: What causes the blower motor resistor to fail?
A: The most common cause is heat buildup. The resistor dissipates heat when running on lower speeds, and over time, the thermal cycling cracks the solder joints or burns the ceramic resistor. In the EX35, I’ve also seen the blower motor drawing too many amps (worn bearings) which overheats the resistor. Another factor is moisture—if your cabin air filter is clogged or you park in humid climates, condensation can short the resistor. On a 2013 EX35 I worked on last winter, the customer had a leaking windshield cowl that dripped water directly onto the resistor. Replacing the resistor plus fixing the leak cost $180 total.
Q: Will a new resistor fix the fan speed issue permanently?
A: In most cases, yes—I’d say 90% success rate. But if the underlying cause is a failing blower motor drawing excessive current, the new resistor will burn out within 6–12 months. I always recommend testing the blower motor’s amp draw before installing the new resistor. A healthy motor draws 6–10 amps on high. If you see 15+ amps, replace the motor too. Also, if the old connector was melted, replace the harness pigtail (costs about $15) to prevent a repeat failure. I’ve seen customers skip this step and come back in 3 months with the same issue.
Q: Real case: 2018 Honda Accord EX with similar symptoms
A: I know this guide is for the EX35, but I want to share a recent case that illustrates the diagnosis process. A customer brought in a 2018 Honda Accord EX with the complaint “fan only works on high.” The owner had already bought a resistor online and replaced it, but the issue returned in 2 weeks. I started by checking the blower motor amp draw—it was pulling 18 amps on high, nearly double the spec. Then I inspected the motor’s bearings—they were dry and grinding. The solution: replace the blower motor ($110 for a Denso unit) and the resistor ($45). Total labor was 1.5 hours at $120/hour. The final cost was $335, and the customer has had zero issues in 8 months. The lesson: always check the motor first if the resistor fails quickly.
Q: How do I verify the repair is successful?
A: After replacing the resistor, test all four fan speeds from the dash control. Each speed should produce a distinct airflow change—low should be barely noticeable, medium-low should be gentle, medium-high should be strong, and high should be full blast. Also, check that the connector isn’t getting hot after running on medium for 5 minutes. If it’s warm to the touch, you may have a high-resistance connection. I also recommend cycling the A/C and heat to ensure the blend door isn’t affected. Normal operation: the fan should respond immediately to control changes without delay or noise.
Q: How long does a blower motor resistor last?
A: In my experience, a quality resistor (OEM or Denso) lasts 5–7 years under normal use. Aftermarket units vary—I’ve seen cheap ones fail in 18 months. The lifespan depends on how often you use the fan at low speeds (which generates more heat), the condition of the blower motor, and environmental factors like humidity. On the EX35, I recommend replacing the cabin air filter annually—a clogged filter increases resistance and makes the motor work harder, which stresses the resistor. Preventative maintenance: every 2 years, inspect the connector for corrosion or melting. If you see any discoloration, replace the pigtail proactively.
Q: Safety disclaimer?
A: Safety Disclaimer: This guide is for educational purposes. Always consult your vehicle’s service manual for exact procedures and torque specs. If you’re uncomfortable with electrical diagnosis or removing interior panels, seek professional help. Disconnect the battery before working on any electrical components to avoid short circuits or airbag deployment. Working on a vehicle’s HVAC system involves moving parts and hot components—use caution and wear safety glasses.
