Your 2009 Ford Focus coupe has an adaptive learning computer that relies on relays and switches to help control the amount of current distributed through the vehicle's electrical system. If the wipers malfunction and you rule out other malfunction sources, then you may have a damaged or broken wiper power relay that you can replace yourself.
Disconnect the battery. Unlatch the cover from your Ford Focus' engine compartment power distribution box that houses the wiper power relay.
Pull out your wiper power plug-style relay located in the center of six medium-sized blocks at one end of the box (labeled as the 31C block on your power distribution box diagram).
Check the box area for any dirt, corrosion or damage that may have caused the relay to malfunction and clean or repair any area as needed.
Push your replacement Ford Focus wiper power relay firmly into the empty relay socket. Remember to check that the relay isn't loose, as current running through a loose relay can cause the relay to overheat or the outer casing and surrounding relay casings or box cover to melt.
Return the cover to the box and reconnect your battery. As your Ford Focus has an adaptive learning computer, you must reset the computer before testing the relay.
Reset the computer by following these steps: set the parking brake and gearshift to park, turn off all accessories, start and then idle your engine for at least one minute, turn on your air conditioning and continue to allow the engine to idle.
Test the wipers to see if the relay corrected the malfunction. If they work, continue with your computer reset by driving your Ford Focus at least 10 miles (to help the transmission relearn). Finally, reset the clock and radio presets.
Inspect your old relay's circuit board solder with a magnifying glass for joint damage or microscopic cracks before throwing it away. Current resistance in the relay followed by a voltage drop that may have caused your wipers to malfunction. Repairing the wiper power relay with your soldering set may help to restore the relay for future use.
Never work on any part of the electrical system in your Ford Focus without first disconnecting the battery, as you run the risk of an accidental electrical surge that could hurt you or cause costly damage to your vehicle.