98 Taurus charging trbl.

my 98 Taurus is not charging. I've tested the large red wire from the alt to the mega fuse all is good, I've pulled the alt, had it tested at auto zone, it tested good. tested the battery, its good. Its not charging at all.
Any Ideas what to check next ?????

Thanks
Mike

You'll need to make some voltage tests to get some indication of what's happening. I'd suggest making these three checks - voltages measured directly across the battery terminals:

Voltage after sitting parked overnight, but before starting engine - should be around 12.6V (indicates that there is no excessive current drain with the ignition in the Off position, and that the battery is capable of holding at least some level of charge).

Voltage with engine idling - should be towards the high end of thirteen-point-something volts - maybe as high as 14V (indicates that the alternator is producing output current, and that that current is reaching the battery. Also indicates that the rectifier is functioning, converting AC to DC).

Voltage when revving engine slightly - should climb to around 14.2V and then hold steady at that voltage regardless of further increase in engine speed. (Indicates that the voltage regulator is functioning, and clamping the upper voltage threshold at the correct level).

I would expect to see an anomaly in one or more of those voltage readings, and that should hopefully point you in the direction of the fault.


Edit: You could also check fuse #26 in the engine compartment fuse box - that's the 30 amp Alternator Fuse.

Thanks for your help.
I did check for any drian on the battery, none found. it will hold a charge as long as nothing is on. 12.6 is exactly the ready I get with the car off. after a start and while running it goes to 12.3 and will drop if anything is running.

I will check the fuse you refer to . I am wondering about the Auto Zone test at this point, the guy really didn't seem to know what he was doing. first test it failed all, then he tested agian after changing conections and it passed all tests

thanks
Mike

A battery voltage of 12.6 with the engine off is good, but the reading of 12.3 with engine running tells us that either the alternator is producing no output current, or if it is then it's not reaching the battery.

With a bit of luck it will just be a blown alternator fuse. If the fuse proves to be ok though, could you let me know which model of Taurus it is - I don't have wiring diagrams for the '98 but I have them for the '97 and there are two charging systems:

1. Charging System, 3.0L 2V, 3.0L 2V FFV
2. Charging System, 3.0L 4V, 3.4L SHO

So if you could let me know which one of those would cover your vehicle. Thanks.

Well after fooling with this problem for days, I went with my gut feeling and lucked out.. I got a alt from a salvage yard and replaced it.... Works great charging 14.3 with car running..
Can't trust some of the Auto Zone counter people to know how to test alts.
Thanks for all your help
Mike