This 2008 Chevrolet Cobalt came in with the complaint that the blower motor did not work at all. It had been working intermittently. Looking under the passenger side of the dash behind the glove box I found the two wire harness connector at the blower motor.
The brown wire should have had battery power on it with the ignition on. It had no voltage present.
The orange wire should have had a full switched ground signal on it with the blower switch at the high position. The amount of battery ground will change if the blower switch is at any of the lower speeds. It will go open if the blower switch is in the off position. The ground circuit tested okay. The ignition does not have to be on to check the ground circuit.
The next logical place to test was at the blower relay. It is listed on the fuse block legend as the HVAC relay at position #30. I did a quick test by feeling the relay and switching the ignition to see if the relay clicked. It did and that proved that the circuits to the terminals 85 and 86 of the relay were working. Next I confirmed that there was battery power at terminal 30 at the relay socket. It was present. If it had not been present I would have proceeded to the BCM 3 fuse in the underhood fuse block for further testing. I then used a fused jumper wire and connected terminals 30 and 87 together in the relay socket.
This should have sent power directly to the blower motor but the motor still did not work. Testing again at the blower motor found that power was still missing on the brown wire.
I had already consulted the wiring diagrams for this system before testing so I knew that there was an in line harness connector (X210) at the far passenger side of the dash. To locate it I removed the glove box assembly starting with the cable retainer at the right side of the glove box.
To do this the outer edge of the black clip has to be lifted slightly so the the clip can be slid towards the front of the glove box and removed.
The stop peg on the left side has to be pushed inward to release the left side of the glove box.
When the glove box swings fully down it exposes the hinge pins. The right one has to be lifted slightly and then that corner of the glove box has to be pulled towards the seat. Then the center one needs to be dropped down. Finally the left one has to be lifted up and the glove box again pulled towards the seat.
I had found this connector without pulling the glove box out but I found it easier to see and work with the glove box removed. A close look at the next picture reveals darkening of the brown wire insulation near the connector. I tried to pull the connector apart but it was melted firmly together.
I simply cut the in line harness connector out and spliced the wires back together. I made sure that the ignition was off so that I would not blow the fuse that powers the brown wire.
Later I used pliers and a screwdriver to separate the old connector and exposed the burnt terminal.
After repairing the faulty wiring connection I used a headlight bulb and harness connector with the appropriate terminals installed to check power and ground at the blower motor connector. I already knew that the blower motor was now working correctly but I just wanted to show another test method for those that may be interested. Caution should be used in doing this test as the bulb can get very hot. Safety glasses are also recommended as the glass portion of the bulb can shatter. It is safer to do this test with a sealed beam headlight.
The next picture shows the light burning dimly with the lowest blower speed selected.
Blower speed 2 selected.
Blower speed 3 selected.
Blower switch set to high, speed 4.
The varying light intensity is caused by the ground supply voltage being reduced through the blower resistor. High speed bypasses the blower speed resistor on the orange wire.
I prefer using a headlight style bulb as opposed to a regular test light as it requires more current to operate it. The same test with a regular test light will not show as distinct a difference between the blower speeds.
An additional note to this repair was that after the system was back working I found that the blower speed would change if the connector to the blower motor was wiggled around. I disassembled the connector and re bent the terminals spring tab in order to tighten its connection to the mating blower motor terminal.