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Jerry, Auto Mechanic
Category: Ford
Satisfied Customers: 2948
Experience:  Mechanic with over 30 years experience with N.Y.P.D. fleet service division
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Electrical system problems 2003 Ford Taurus SES 6cyl.

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Electrical system on 2003 Taurus SES 6cyl went haywire. Check lights on dash come on: 1. batt, abs/break(one or both), radio only squeals, elec windows don''t come down. This happens, parked with engine running. Intervals of lights on/off diff. Avg on 15sec, off 30sec. Testrun same except trany shifts rough and door locks go up and down also, lights on/off interval diff each time as is combination of lights. When parked and hood closed I hear a click, like a solenoid when checklights come on. Battery is full. Voltage is normal 12.3 with engine off and 14.5 with engine on. Alternator keeps on charging normal. My guess is lose ground wire but have no clue how to go about in finding it. Can you help me?
Hello Springer, the quickest way to check for a poor ground circuit is to make a jumper wire with an alligator clip on each end, connect one clip to the battery negative and the other end to a clean paint free area on various parts of the body,cowl area.This will eliminate any voltage drop in the ground circuit. If the circuits start to work, a permanent ground wire connection can be installed.I could send you info on voltage drop testing that would require a digital voltmeter. This test is quicker and easier to use.
Customer: replied 9 years ago.
now since you mentioned it, I checked the wire from the negative batt terminal to the car body. It is tight and ok.
You can leave the clamp on the negitive battery,try different parts of the body,and on the engine block and alternator housing.
Customer: replied 9 years ago.
thanks for your responses Jerry. I tried what you told me, but no change. The ground wire from the battery is properly connected, I made several tests to other parts of the engine block and fenders,the connection is ok.

But I made some observations that I did not know before.
1. when engine is running, check lights on, and I turn the fan-motor on higher speeds, check lights go off(almost everytime, 4 out of 5 times).
2. with check lights off(above condition) and hit the gas, check lights come on again and headlights and interior-lights go brighter for a moment. My foot off the gas and everything is perfect again, no check lights. I checked the voltage during all of this, all normal values except with higher RPMs charging voltage goes up to 16.2 or 3.

I can't make any tests tonight anymore. Since the negative cable connection is not the problem, is there anything else you can recommend, Jerry? Thanks for all the help so far. Can I work with you tomorrow again, how does this work?
Hi Springer, the charging voltage is out of range,the normal voltage is 13.8 to 14.8 volts at an engine speed of 1500 rpm and above. The readings you have indicate an overcharge condition. That can be causing the problems you are having. I would have the charging system and the battery tested. I have seen a defective battery cause some strange electrical problems. You can post to your question at any time,it will remain open .Jerry
Customer: replied 9 years ago.
Jerry, the battery is brand new. I had to get rid of the old one because it could not be charged anymore past a quarter full, also it had at least one bad cell. That battery showed the same high charging voltage of 16.2, but not all the time. The new one is fully charged and does the same thing but only when the head lights, the bright lights and every other electrical accessory in the car is turned ON and the engine racing.

It did not click at first when I saw those high values, but could the voltage regulator in the alternator be bad?
Hi Springer,the voltage is too high.I would look into the charging system problem first.It most likely will correct the other problems you are having. The systems are designed to operate in a specific voltage range. To high or too low ,they can not function properly.
Customer: replied 9 years ago.
It makes sense that the charging system is the problem but I would like to know where and what I can check to make sure what in particular it is. For 2 reasons, it might be something I can do myself, or if I have to take the car to a garage I don't want to pay for something that does not need fixing, and the real problem is still there.

My electrical/electronic knowledge on these late model cars is limited, including how some of the parts look like and where they are be located. This is a little more complicated than the elecrical system on my old muscle cars.

Thanks for your help, Jerry
Hi Springer, I have been doing some research on your problem,there is a voltage regulator in the alternator,but the charging system is also turned on and off by the engine control computer.All problems concerning the computer were no charge conditions. I would look at he connections on the alternator ,make sure the are fully seated into the alt.If they look good,if you are going to do the work yourself,remove the alternator and have it bench tested.If it is overcharging ,the regulator can be replaced,no need to replace the complete alt. If you do the regulator,I would recommend getting a Motorcraft,others brands have been troublesome. .
Jerry and 4 other Ford Specialists are ready to help you
Customer: replied 9 years ago.
Thanks Jerry, I will check out the alternator and the voltage regulator.

We have here in northern Ohio a nice snow storm going. I don't think I'll get to my problem for a few days. It is to cold and stormy.

I let you know how it turns out.

Take care

Hi Spinger, thanks for accepting.We are due snow here tomorrow. Please let me know what you find.Jerry