First of all, you're dealing with an intermittent problem. Those are always the most frustrating to find because you never know for sure if you really found the cause.
Second, you have to do any diagnosis while the problem is acting up. The generator, or whatever is really the cause, is going to test good when the problem isn't there.
Based on your description and the need for a jump-start, it really sounds like a charging system problem. The generator is just one part of the system. The voltage regulator is most likely built in, but there's still wiring to consider.
When they changed the battery, they would have cleaned and tightened the cables. The connections right at the battery wouldn't exactly cause the symptoms you described, although they could prevent the battery from charging completely. A jump-start would take care of starting, but I don't think the dash or turn signals would be affected. Since you noticed the problem occurred when higher current was needed for the signals, that suggests a bad electrical connection somewhere else. The most common cause I read about repeatedly on many brands of cars is that positive wire at the fuse box, but there are many other places for bad connections or corroded splices to occur.
If the things we recommended so far don't pan out and the problem continues to occur, the goal should be to try to keep the problem occurring so it can be found and corrected. Too many people wiggle and poke at things until something "fixes" it, but we know it's not really fixed.
You might not get any fault codes. They are mainly for things that can have an adverse effect on emissions. Low system voltage can do that but the conditions needed to set a related code might not have been met.
The most helpful thing you can do for now is to take the voltage readings at the battery. You might also see what happens when the problem is occurring and you stop the engine. See if the head lights are bright or dim, if the turn signals work, and anything else you can observe. At that point, measure the battery voltage again. You'll read 12.6 volts if it's fully charged. In that case, work your way down the battery wires to the fuse box and body to try to find a place where the voltage drops lower. Leaving the head lights turned during that test will make it more accurate as the current that can't get through the bad connection will make the problem easier to spot.
If you find closer to 12.0 volts at the battery, it is good but discharged. That will prove something isn't working in the charging system.
You might also look at the fuses themselves. Turn signals don't take a lot of current so they really shouldn't cause much trouble in high-current circuits like the smaller battery cables, but in a circuit that is only meant to handle that lower current, a corroded fuse terminal or partially broken wire will be affected greatly by the added current of the signals. I have a vehicle here right now that is missing the cover to the under-hood fuse box. Two of the fuses completely corroded away from the water that sprayed up there. If you push a fuse and the problem clears up, check the terminals for signs of corrosion.
Hope that gives you some more ideas. Holler back with those voltage readings.
Friday, August 12th, 2011 AT 7:42 AM