1. Check the Fuses: This is the absolute first thing to do. Your owner's manual will show you the fuse box location and the fuse ratings for the power windows. A blown fuse is the easiest and cheapest fix. Replace any blown fuses with fuses of the *exact* same amperage rating.
2. Power Window Switch (Master Control): The master switch in the driver's side door is the most common point of failure. These switches are prone to wear and tear, especially after 30+ years.
* Testing: Try each window switch individually. If none work, it's highly suggestive of the master switch. If one or more individual windows work from their own switch, but not the master, the master switch is the likely problem.
* Repair/Replacement: You might be able to disassemble the master switch and clean the contacts with contact cleaner. However, this is often temporary, and a replacement switch is usually the better long-term solution. These switches are relatively inexpensive and available online or at auto parts stores (specify it's for a 1987 Cadillac Deville).
3. Power Window Relay: Older Cadillacs may use a relay to control power to the windows. This relay can fail, cutting power to all windows at once. Locate the relay (your owner's manual or a wiring diagram will be helpful) and test it for continuity or swap it with a known good relay of the same type (if you have a spare).
4. Wiring Issues: A break or short in the main power window wiring harness is possible. This is more difficult to diagnose and repair.
* Visual Inspection: Carefully examine the wiring harness in the driver's door, particularly where it bends and flexes. Look for any obvious breaks, cuts, or chafing.
* Continuity Testing: If you have a multimeter, you can test the continuity of the wiring harness. This requires some electrical knowledge and a wiring diagram.
* Ground Connection: Poor grounding can also cause intermittent or complete power window failure. Check the ground connections for the power window system.
5. Power Window Motor (Less Likely): It's less probable that all motors failed simultaneously. However, if all the above checks out, this becomes a possibility, though it would be costly to replace all of them at once.
6. Body Control Module (BCM) (Least Likely): While possible, this is less likely as it's a complex computer module. A BCM failure would probably manifest in other electrical malfunctions as well.
Where to Get Parts and Information:
* Online Retailers: Sites like eBay, RockAuto, and Amazon often carry parts for older Cadillacs.
* Auto Parts Stores: Local auto parts stores can help identify parts or offer alternatives.
* Cadillac Forums: Online forums dedicated to Cadillac Deville owners are invaluable resources for troubleshooting advice and parts sourcing. Searching for your specific model year and problem will likely yield similar issues and solutions.
Important Notes:
* Disconnect the battery's negative terminal before attempting any electrical repairs to avoid short circuits.
* Consult a wiring diagram: A wiring diagram specific to your 1987 Cadillac Deville will be crucial for tracing wires and identifying components. You can often find these online.
* Safety First: If you're not comfortable working with car electrical systems, it's best to take your Cadillac to a qualified mechanic.
Start with the fuses and the master switch. These are the most likely culprits and the easiest to check. Work your way down the list, testing each potential issue before moving on. Remember to always prioritize safety.
