2016 Jeep Wrangler Blower Motor Diagnosis: Finding a Faulty Relay

Initial Diagnosis and Scan Tool Check

• 💡 A 2016 Jeep Wrangler presented with a non-functional blower motor.
• ⚠️ A flashing rear defroster light was noted, but other climate controls seemed to function.
• 💻 A scan tool was used to check for HVAC codes; only a code for the recirculation door's travel range was found, which was deemed unrelated.
• 📊 Data stream analysis showed the front blower speed potentiometer voltage recognized inputs from the control switch, indicating the switch itself was likely functional.

Wiring Diagram and Component Identification

• 🔍 The technician consulted wiring diagrams, noting the Jeep uses a computer-controlled system, referred to as MTC (Manual Temperature Control).
• 🔌 The blower motor assembly appears to be a combined unit with a three-wire connector: power, ground, and control.
• 🛠️ Mitchell On Demand diagrams were found to be unreliable, leading the technician to prefer OEM diagrams for accuracy.

Testing Power and Ground

• ⚡ A heavy-duty test light was used to check for power and ground at the blower motor connector.
• ❌ No power or ground was detected on the blue wire (power) or black/white wire (ground), indicating a problem upstream.

Fuse and Relay Inspection

• 🔍 The fuse box (TIPM) was inspected for the blower motor fuse (J15, 40 amp) and relay (K9, front HVAC relay).
• ✅ The fuse appeared visually good, and power was confirmed at the fuse.
• 💡 The front HVAC relay (K9) was identified as a potential culprit.

Relay Testing and Replacement

• 🧪 A homemade relay testing tool was used to check the control side of the relay (terminals 85 & 86), confirming it received power with the key on.
• ⚠️ However, power was only found on one terminal (terminal 30) of the output side of the relay, indicating the relay itself was faulty.
• ❌ A temporary swap with the radiator fan low relay (which had the same part number) confirmed the blower motor worked, proving the original relay was bad.
• 🔥 Attempting to use a different, non-identical Chrysler relay resulted in smoke, highlighting the importance of using the correct relay part number.

Conclusion and Key Takeaway

• ✅ The blower motor issue was resolved by replacing the faulty front HVAC relay (K9).
• ⚠️ The video emphasizes that a relay is not just a relay and stresses the importance of proper testing and using the correct part number to avoid further damage.
• 🧠 Gathering information and performing systematic testing is crucial before replacing components like the blower motor itself.