Lights keep going out

Maintenance/Repairs
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1

I have a 2004 Ford Focus with 120,000 miles on it. In the past 8 months I have had to replace both rear brake lights twice and both of the head lights. I also had my mechanic replace one break light in addition to the ones I did. On one occasion some one told my wife her break light was out at a traffic light. When I got home and checked the light was working. The only other electrical problem I have noticed is that the emergency break light goes on now and then and also the check engine light. If this is a wiring or electrical problem is it something that will be able to be fix or even found? Also is it going to cost more than it is worth for an older car?

2 
 That sounds like it may be over voltage.   That is easy to check

   That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here.
3

I agree with Joseph about getting the codes read and posted. Or take the car to a real shop and get it checked out. I think the head lights and brake lights are not related to the check engine light. As far as replacing both head lights (I assume only once) since they were the same light, the same age, and come on together they will burn out at nearly the same time. As for the brake lights I’d look for a loose connection or faulty ground.

4

I agree about checking the alternator voltage to see if there is excessive voltage causing the lights to fail before they should be normally. The DC voltage should be no more than 14.8 volts while the engine is running around 2,000 RPM. Also check the AC voltage across the battery and make sure it is less than .1 volt.