How to Troubleshoot the Electrical System in a Ford F-Seriesby Contributor
The Ford F-series is the standard in American pickup trucks. The more popular F-150 comes with a decent electrical system; however, those needing a heavy duty truck like the F-250 might experience more problems with the electrical system due to the power supply demands.
Look to your alternator if starting your car provides you with a click instead of an engine roaring to life. However, even a truck that starts can have alternator problems. Check the headlights while the pickup is idling; if they get weaker, you may have a loose alternator belt or loose connections. Rust also affects the Ford alternators.
Have the Generic Electronic Module (GEM) tested or scanned for fault codes if your windshield wipers don't turn on. This will tell you where the problem lies. The GEM controls all electrical items.
Check whether you have electrical problems after your truck sits in the rain. If so, your windshield may be leaking onto the GEM, located behind the passenger fusebox.
Watch the gauges on your dash when you start your engine. If it takes the gauges awhile to wake up, they're not getting their dose of voltage from the battery. Get your battery checked.
Find out if multiple electrical problems are related by checking the battery first. Sometimes, if a cell drops in the battery of a Ford truck, the electrical system goes haywire. Otherwise, the problem might lie in the Body Control Module, a cluster or a pinched wiring harness.
See if wire conductors are the problem. Metal fatigue isn't a common problem in the Ford pickup, but sometimes a lot of off-road driving can affect the wire mounting points.
Use the Power Distribution Terminal (PDT) if you need to power up devices that create a large power demand. Located at the starter solenoid, the PDT is always "hot."