2003 Chevrolet Silverado 5.3, Brake Lights Illuminated and Blower Motor is Inoperative.

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.

2000 Chevrolet C3500 5.7, Wipers and AC Inoperative

This 2000 Chevrolet 3500 came into the shop with a couple of complaints by the customer. He said that a few days before both his AC and windshield wipers stopped operating.  He had checked a couple of fuses, but was unable to find a problem.

First things first, I confirmed the customer's concern.  The AC and the wipers were inoperable.  Next thing to do was to pull up a wiring diagram and start checking the circuit.

I first checked out the two fuses in the fuse block on the left-hand side of the dash.  The wiper and AC fuse are next to one another.  At first, I wondered if something might be going on with the terminals.  When I checked the fuses (Fuse 11 Wiper 25A and Fuse 12 HTR-AC 25A) with KOEO (Key On Engine Off) and the AC and wipers in the on position, I got ground.  No power was coming to the fuses.

Now that I knew there was no power to these two fuses, it was time to find out what their power source was.  Again, consulting the wiring diagram, I saw power was supplied to these circuits by the IGN B 50A fuse.  I saw the radio was also powered on this circuit, and when I checked the radio, as expected, it did not work either.  The IGN B 50A fuse is located in the Power Distribution Box under the hood, on the left (driver's) side of the engine compartment.

The fuse I'm pointing out is the IGN B fuse.  When I checked it with the Power Probe it showed one side with power and the other side without.  This meant we had a blown (melted) fuse.  I replaced the fuse, turned the key to KOEO and tried the problem circuits.  They all now worked.

Of course, fuses don't just blow for the fun of it.  When I reported my findings to the customer, telling him we would need to do further diagnostics to determine the cause of the blown fuse, he opted to pick it up and run it until he has any more trouble out of it.

I advised him on the potential problems and inconveniences that could result from this; but, he decided to pick the truck up as is anyway.

I just hope it doesn't decide to blow when it's raining!