This 2003 Chevrolet Silverado 5.3 came into the shop with several customer concerns. The major concern was that the AC was inoperative. He mentioned the AC had stopped working within the last two weeks or so and (another concern he had) his brake lights (both the ABS and red brake light) had come on at the same, or about the same time.
First things first, I confirmed the customer's concern. With the AC on (the control panel lights were on and showing the AC was on), going down the road, cold air would blow in. When you stopped the vehicle, no air at all. The brake lights also were illuminated in the panel as the customer said.
Next thing, pull out a wiring schematic and do some checking on the circuit. It was obvious from driving the vehicle down the road (and observing it visually) the AC clutch was working and the compressor was cycling.
Since the blower motor resistor was fairly easy to access, I started there. With a test light I checked for power on the respective wires to the resistor. The Power Probe showed no power on any wire at any speed. The feed wire also showed no power.
(This is why it is important to "test and not guess". I have seen a lot of people just throw a resistor in there, because they "go out all the time" only to have it not work. Make sure you know the cause of the problem before you start removing and replacing parts. R&R of parts can cost you a lot of time and money. The best solution is to take it to a professional and get it done right the first time.)
Next, I went to the fuse panel in the left side of the dash.
No power at the fuses.
The brake fuse and HVAC fuse are supplied power by the ignition switch. An orange wire supplies voltage to these fuses. Probing this wire, as expected, I found no voltage.
It was time to replace the ignition switch. The ignition switch is an electrical component. It is not the part you put the key in to start the vehicle . . . that part is the key and cylinder or tumbler. Some ignition switches will come with a wiring harness. This one did not.
To access the switch, remove the steering covers and the tilt handle. To remove the handle pull outward. Sometimes a pry bar or long screwdriver may be necessary. Just be sure not to break any of the plastic surrounding it.
The switch is located on the bottom of the steering column. It is located just below the lock cylinder.
Disconnect the holding tabs (2 white tabs, one on each side) and gently pull down. Next remove the wiring harness. The switch by itself is shown from a couple of angles below.
Once the switch was replaced and installation was completed, it was time to try out the AC and see if the brake lights were now off in the dash. Sure enough, the brake lights were no longer illuminated and the blower motor was now operational.
The high speed was inoperative, but the customer said it had been so for several years and declined to have it repaired.
