1. Locate the Blower Motor Relay:
The relay location varies slightly depending on the exact model year and trim level of your 2002 Cadillac DTS DeVille. However, it's typically found in one of these areas:
* Under the hood: Check the fuse box located near the battery. The relay may be labeled, or you may need to consult your owner's manual or a wiring diagram to identify it.
* Under the dashboard: Some relays are located within the interior fuse box, often accessible under the dashboard on the driver's side. Again, your owner's manual or a wiring diagram will be helpful.
2. Test the Blower Motor Relay:
Once you've located the relay, you can test it in a few ways:
* Visual Inspection: Check for any obvious signs of damage, such as burnt contacts or a cracked casing.
* Swap with a Known Good Relay: The easiest test is to swap your blower motor relay with another relay of the same amperage rating (check the relay itself for this rating). If the blower works with the swapped relay, the original relay is faulty. If the problem persists, the issue lies elsewhere.
* Multimeter Test: If you have a multimeter, you can test the relay's continuity and coil resistance to verify its functionality. Refer to a relay testing guide for specific instructions.
3. Beyond the Relay: Other Potential Problems:
If the relay is good, the problem likely lies elsewhere:
* Blower Motor Resistor: This component controls the different fan speeds. A faulty resistor can cause the blower to work only intermittently or at only certain speeds. Often located behind the glovebox or under the dashboard.
* Blower Motor Itself: The motor itself could be failing. Worn brushes or a damaged motor winding can cause intermittent operation.
* Wiring and Connections: Check the wiring harness leading to the blower motor for any damaged, loose, or corroded connections. Pay close attention to the connections at the blower motor resistor and the blower motor itself.
* Control Module (BCM): In some cases, a faulty Body Control Module (BCM) can cause intermittent blower issues. This is a more complex issue requiring professional diagnostics.
* Fuse: Though less likely to cause intermittent problems, a failing fuse can act like a weak relay. Check the related fuse(s).
Troubleshooting Steps:
1. Start with the easiest: Visually inspect the relay and swap it with a known good one.
2. Check the fuse: Ensure that the blower motor fuse is intact.
3. Inspect wiring and connectors: Look for damage or corrosion in the wiring leading to the blower motor, resistor and relay.
4. Test the blower motor resistor: This is often the culprit for intermittent blower problems. Accessing it might require removing parts of the dashboard.
5. Consider the blower motor itself: If all else fails, the motor might need replacement.
6. Professional Diagnosis: If you're not comfortable with electrical work, a professional mechanic can diagnose the issue accurately and efficiently. They have diagnostic tools to pinpoint problems that are harder to trace.
Remember safety first! Disconnect the battery negative terminal before working with any electrical components. Consult your owner's manual or a repair manual for your specific vehicle model for detailed diagrams and instructions.
