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I've been having some electrical issues with my 2005 Focus. I apologize if this same issue has been raised in the past. About a year ago, it did this thing where it made a clicking noise that sounded to be coming from the steering wheel/dash area. At the same time, the headlights were flickering and the radio would turn on and off. Once the vehicle was turned off, the battery was completely dead and had to be jump started. I didn't happen again for about 6 months. It has now happened about 4 times in the last 2 weeks. It has been taken to 2 different mechanics (one of which was the Ford dealership), but they could not find any problems with the battery, alternator, etc, and of course the problem won't replicate itself when its at the shop. Any suggestions on what we should try next?
 

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Do you still have the factory battery terminals on the car? These are what's called a "wedge" clamp style. I can show you a pic if you're not sure, but instead of a bolt that goes horizontally through one end of the terminal to clamp it shut, there's a nut on top with a stud wedge that goes down into the the terminal. There's also a nut and stud that hold down some of the wires that go to the wiring harness. The negative terminal is the one that caused my problem- not the terminal itself, but the wires connected to it. It wasn't easy to find either. I disconnected the wires that were bolted to the terminal and found one that the ring connector was nearly broken. It was barely making contact- but looked like it was in place. It didn't cause a no-start issue, but it could because one of those wires provides the negative for the relay box so that the relay coils work. That's another place to look into, but you must disconnect the negative battery terminal before checking the hot or the negative connections at the relay box under the hood. Loosen, remove, inspect, clean, re-install on all, and don't assume because it looks ok that it is.

Another big charging system uh-oh that is often overlooked is the negative battery connection to the engine. This won't always cause a no-start issue because there is supplemental chassis to engine grounding on all vehicles, but that grounding is not designed to handle the sort of load that the starter or even the electronics create. If that wire is loose, or its terminal is cracked, then that will cause intermittent problems until it breaks completely. On your car it is bolted to a one of the engine to transmission bolts, but you'll have to remove the battery or get under the car to get to it. This should be carefully inspected using the same procedure. Unless an electrical connection is disconnected, inspected thoroughly, cleaned, and then re-installed- it can still be suspect. I have a good bit of experience with electrical uh-ohs, and believe me, looking at something to be sure it's ok doesn't work 100% of the time. You might be dealing with one of those rare instances.

Another point to check- although it shouldn't cause an intermittent non-start issue is the radio interference capacitor. At the front of your engine, on the firewall side, there is a black box with a single wire going to it, and a single wire coming out of it going to the shock tower where it is grounded to the chassis. This wiring can become damaged over time, cracked, exposing the conductors. It's deceptive because on the side of the box opposite the wire that is grounded, that wire is hot. If the hot side shorts out, it blows the ECU fuse, and no start, no nothing. If the ground side becomes partially disconnected then it causes radio noise (not just from the AM radio) to be introduced into the power supply for the ECU. That's why it's there. Your computers could become damaged if it is left without the interference capacitor for a long time. I do not think that's your problem, but I wanted you to be aware of it so that you can look at it every time you change the oil, and if you get a no-crank/no-start issue but still have power in the car, you might want to check that fuse and secure the wiring if it is shorted. That knowledge could save you from a tow [thumb]
 
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