Re: 99 Expedition Running Board Lights Timeout
Check for any DTC's? (You can go to autozone and have them scan your Expo.)
Common error codes you would get in relation to this are B1313 -- B1316 These would indicate a battery Saver Relay Coil Circuit issue. Fix is to replace or check the ground on it depending on the dtc itself.
Another possible error code would be B1342 This would indicate that you should replace your GEM(Generic electronic module). Most likely you would see issues with your drivers window, warning chimes, wipers and other items along with the Running board lights and interior lights not turning off. It is highly unlikely that this is the problem, BUT a quick scan at AZ will confirm this.
If you are not getting any B codes then you can check the voltage on the battery saver relay. Remove your keys from the ignition and measure between the connector pin 5 and ground. If there is no voltage you will need to replace that relay again. If there is voltage then check the Fuse junction Panel. At the FJP you will want to test Circuit 705(LG/OG - Light Green/orange) wire and ground for a short to power. Make sure that the key is set to the #2 position.
Hope this is some help. If you are confused/dont understand any of this then I would suggest you take the SUV to the dealer and have them check the GEM for any problems.
Simple tests such as code scanning can be one by Autozone or even a good dealer at no cost to you. Check for exposed or frayed wiring. These can be most likely the cause of the problem and it is recommended that the dealer replace these, unless you are highly capable of this yourself.