This 2003 Cadillac Deville DTS came in with the complaint that the blower motor does not work most of the time. Sometimes it will blow but it seems to blow slower than it should. Using a test light and a jumper wire, I connected one end of my test setup to the purple wire.
Then used the tip of the test light to gently probe the black wire. With the key on and the blower set to high speed, the test light lit up. Indicating that power and ground were both preset. At least in an unloaded condition. Since worn out brushes are common on these motors. I gently reconnected the harness and flexed the motor connector back and forth. The motor would work under these conditions so the diagnosis is a faulty blower motor assembly.
The blower motor is pretty easy to change. Just three screws hold it on place. I think they were 6 mm.
There are two different blower motor part numbers listed for this car. One has a foam gasket and the other has a rubber gasket as shown below.
This car has more problems, in that this was just laying on the inside of the hush panel when I removed it. It is the passenger side temperature door actuator.
It mounts the the end of the heater-a/c case behind the glove box area. the glove box has to be removed to install it.
As the customer is currently financially challenged, I do not have anymore picture or information at this time.