Where is the blower motor relay or control module on a 98 deville theres power going to and was tested it works fine but wont come in vehicle?

The blower motor relay and control module locations on a 1998 Cadillac DeVille aren't always in the same place, and there's no single definitive answer without more specifics. The relay *might* be in the underhood fuse box (often called the Power Distribution Center or PDC), or it could be inside the car's interior fuse panel (usually located under the dash, often near the steering column). The control module is *more likely* to be inside the car, potentially even integrated into the HVAC control panel itself (making replacement more complex).

To find them, you'll need to do the following:

1. Consult your owner's manual: This is the first and best place to look. The manual should have a diagram of the fuse box(es) and relay locations.

2. Check the underhood fuse box: Carefully examine all the relays in this box. Many are interchangeable, so you may need to consult the diagram in your manual to identify the correct one. Look for relays labeled "blower motor," "HVAC," or something similar. If you find one, test it with a multimeter, even if you already tested it, to ensure it's not intermittently faulty.

3. Locate the interior fuse panel (underdash): This is usually accessible by removing a panel or cover. Once located, carefully examine the relays and fuses. Your owner's manual will have a diagram of this panel as well.

4. Check the HVAC control panel: Sometimes the blower motor resistor (not a relay but a common failure point) or the control module itself is integrated into or behind the HVAC control panel. This usually means you would need to disassemble the panel to access it, and this is more involved. If you aren't comfortable doing this, a professional mechanic should handle it.

Important Considerations:

* Wiring: Even with a good relay and control module, problems can arise from faulty wiring. Test the wires going to and from the blower motor for continuity and proper voltage using a multimeter. Look for broken or corroded connections.

* Ground: A poor ground connection can also prevent the blower from working. Trace the ground wire from the blower motor and ensure it's clean and properly connected.

* Blower Motor Resistor: This is a common point of failure in blower motor circuits. It's often located near the blower motor itself, and a faulty resistor can cause the blower to only work on high speed, or not at all. It’s worth checking this, as it's a simpler repair than a relay or module.

* Professional Help: If you're not comfortable working with automotive electrical systems, it's best to take your DeVille to a qualified mechanic. Improperly working with car electrical systems can be dangerous.

By systematically checking these areas, you should be able to pinpoint the source of the problem with your Cadillac DeVille's blower motor. Remember safety first – disconnect the battery negative terminal before working with any electrical components.