Re: Battery light stays on but runs fine??
Again , dont know if this helps you . Also read a few articles saying broken wiring at door sheaths can cause this , but really no idea if this is a possible cause . Best I can do to help .
I have a 96 Windstar & had some charging problems as well. I narrowed mine down to a series of faulty NEW alternator/voltage regulators (Good thing they are on warranty).
Don't assume a replacement part is in serviceable condition. One winter I went through 6 rebuilt starters.
I've owned a lot of older cars and run into similar problems on vehicles.
Try this: First ensure your battery terminals are clean and free of corrosion. Make sure you use a battery tool to clean them up to ensure a good connection. reconnect and tighten.
NOTE: Some electrical systems need to have the system computer reset after changing an alternator. If you changed the battery first, then changed the alternator, this may not have happened. Sometimes it's as easy as fully disconnecting both terminals and reconnecting the battery.
Check the voltage from the positive terminal of the battery to the negative terminal on the battery(record this).
Then check voltage from the positive terminal of the battery to where the negative terminal connects to the block. if this reading is lower your negative battery cable may be the problem. I've had them crystallize before from age so badly that they lost flexibility and began breaking internally. Replace it.
Then check voltage from the smaller positive cable post on the alternator and the negative terminal on the battery. If this is lower the smaller cable may be the problem. Replace it.
Then check voltage from where your positive cable hooks up to the solenoid and to the negative terminal on the battery. if this is lower your positive battery cable may be the problem. Replace it.
Charge the battery fully and take the vehicle to a local auto parts store and see if they can run a charging system test (usually a free service). They should be able to tell you what kind of shape your battery is in and the alternator output. A good alternator will put out 14+ volts, if it's putting out 12-14 volts it's wearing out and needs replaced.
If your alternator is putting out 10-10.5 volts or less means one of the diode pairs are bad, 5-5.25 volts or less 2 diode pairs are bad. Either way the alternator is not charging the battery and it's the fault of the voltage regulator.
Ask the person doing the test if he can tell you what the field voltage is on the alternator. If they can and it is around 12 volts or more you can probably bypass the next test.
Start the vehicle and hold a steel tool near the back of the alternator (not on the pulley side). It should be drawn magnetically to the center of the alternator. If it doesn't your alternator is not generating the magnetic field needed, to generate electricity. This could be due to a bad alternator or wiring.
WARNING: The next test is the "old fashioned" way we shade-tree mechanics used to do this. It can be done with the engine running in most cases, but you must be extremely careful that you don't get clothing or long hair anywhere near the pulleys. You do this at your own risk. If you are uncomfortable with taking such a risk, have your mechanic look into it. Disconnect the two wire box-like electrical connector from the alternator's voltage regulator and see if there is any voltage (should be around 12 or more volts DC) from the wires going to the alternator. You can try testing this with the engine shut down and the key on, but it may not work on all vehicles. -
With connector disconnected, if the voltage is less than 12volts or non-existent, it's a wiring problem. - With connector disconnected, if it is 12 volts or above it's probably the alternator (Bad windings.)
Set the multimeter to Ohms. Touch probes together and calibrate the needle to zero on right side of meter readout. (If the needle does not move to the right, you may need to replace the meter's battery or fuse). With the Alternator connector disconnected check the resistance of the alternator at the connector blades. If the needle goes to infinity, there is an open circuit in the windings. Replace the alternator.
Other things that can cause charging system problems:
Excessive starter draw - Remove starter and take to parts store for testing
Failed engine compartment fuses or resisters - Look for and check big rectangular ceramic ones as well on antique/classic vehicles
Failed fusible links
Failing ignition switch - Usually under the dash, Not at the key
Wiring to the key assembly inside the steering column - or on the dash older vehicles
Bad computer modules
Electrical wiring - This one takes the longest to isolate
Particularly hot wires arcing to ground
Some other Windstar threads suggest checking wiring bundles under the rubber boots at door hinges.
Other unassociated electrical components shorting to ground and placing a drain on the system - could be anything from a cigarette lighter, to lighting, to electric radiator fans failing to shut off, ignition coil, radio, sensor probes shorting to ground, etc. etc.