On 1997-2006 Jeep Wranglers (TJ's) the harness that plugs into the back of the control head will burn up. When this happens the inside of the Jeep will smell like burnt rubber and the a/c blower may not work. Below is an outline of the cause of the problem, and how to fix it. Our Tech department spent time to diagnose the problem and figure out a solution.
The three wire connector that connects to the back of the AC/heater control head melts. The common fix for this problem is to cut the factory connector off and replace it with three female crimp-on connectors and plug them into the control head. This temporarily fixes the problems. A short time later you find yourself taking the dash apart again to fix something else in this circuit that has overheated.
We were able to get our hands on a vehicle with this problem so the folks here at Jeepair did a little research to figure out why this is happening. Heat in an electrical circuit is caused by more current flowing in the circuit than the components that make up the circuit are capable of carrying. Now that’s not to say that Jeep did a poor job designing the circuit, something has changed causing more current to flow than the circuit is designed for. What has changed is the blower motor.
On our test vehicle we pulled out the control head and did some temporary wiring around the damaged connector so we could run the blower motor. We measured 22 amps of current flowing on the circuit with the switch set on the high position. We installed a new blower motor and retested. The new blower motor pulled 15 amps of current on the high setting. Our analysis is blower motor failure is root cause of the problem and the only symptom of the failure is an increase in the amount of current required. The overheating damage to the connector is a result of excess current flow caused by the blower motor failure. The connector appears to be at its upper limit of current carrying capacity required by a new motor and once the blower motor begins to fail the connector is the weak link in the circuit.
Our conclusion is you need to replace the blower motor along with repairing the connector.
Can you fix the motor? We took the motor apart and oiled the bearings, cleaned everything up but could not lower the amount of current required by the motor.