very early 91 3.0 battery drainage issue

[Cymrych]

My sister-in-law has a very early 91 Taurus; so early that it has the same motor as the 90 model. A few weeks ago, her idiot light came on warning of a low battery. She had the battery pulled and checked, then replaced. Car was fine for a few days, then the battery went dead. I pulled the alternator, had it checked, and found it was putting out nothing at all. Replaced it, and car was fine for a few days.

Now, if the car sits for more that 8 or ten hours, the battery is stone dead (can't even get the solenoid to click at me!) All fuses are fine, nothing is staying on that shouldn't be staying on, everything seems to function properly, including the ignition cylinder (I remember reading that they could be problematic.) But obviously, something is draining the battery. I'm thinking that I got a bogus rebuilt alternator, but wonder if there might be something else going on.

It figures, she had to have an electrical problem. I could tear down the motor to replace a set of rings in my sleep, but electrical issues are NOT my strong suite. If you suggest a short somewhere, please feel free to dumb any explanation as to how to rectify things; I will not take offense!

[Cymrych]

On a whim, I hooked my circuit tester between the negative wire and the negative post on the battery, and started pulling out all the fuses for stuff which can be turned on without the key being in the ignition. My thought was that if I would pull all such fuses, the only thing left would be the ignition circuit, which would require the key to close the circuit and power the light in my tester.

So, I first pulled all the fuses and breakers for the stuff that can be powered without the key. My test light stayed on. Then I started pulling the rest one by one, figuring that eventually my light would go out, hopefully indicating a circuit that is remaining powered after the car is shut off. Problem was that I ended up pulling every fuse and breaker out of the fuse box, but the test light remained lit.

Are there more fuses somewhere else in the car that I don't know about? Everything I can think of seems to be routed through the fuse box, with the exception of the ignition circuit, but maybe there was something else. If there are no more fuses, it seems to me that for some reason or other, the ignition circuit is remaining closed even though the key is not in the car, draining the battery.

If my logical seems correct, how should I proceed from here?

[shorod]

Check under the hood and see if there is another fuse panel under there.

-Rod

[Cymrych]

Well, I don't seem to see anything like another fuse box under the hood. I presume it's there, or you wouldn't have mentioned it. What's it look like, and roughly where can I find it?

[shorod]

Well, many cars have additional fuse/relay panels under the hood, but I don't have a clear recall of the 91 Taurus underhood, or even my previous 1993 Taurus SHO under hood. I don't really remember one under the hood of the 1993 though.

It would most likely resemble an easily accessible black rectangular plastic box, usually near the outer edge of the engine bay, and would probably say something like "Fuse" or "Relay" molded into the cover.

-Rod

[lectra]

I know my '96 has one, and I believe it's front and center. It's just a black, rectangular box that is about the size of a brick (maybe a little bigger). You pull one end of the box (it has little handles halfway down) to open it, exposing several mega-fuses, as well as smaller fuses. The wrighting on it is probably either printed on (and thus worn off) or embossed into it (which won't wear off). If it's embossed, you need LOTS of light to see it as it will probably not be overprinted to make it visible.

Also, every time I've checked, the idiot-light just warned of a battery charge error. Some older cars may have a "biased lamp" that may only light if the altinator voltage output is below a certain voltage (and thus it may be hard to see, even in the dark). Check that light very closely. You can also, often, bust altinator problems with a voltmeter measuring across the battery. For the most part, if you're not getting more than 14 volts to the battery (often I've seen it backwards!), your altinator is often not doing its job correctly. The altinator could also be leaking electricity backwards when it isn't running! This is often a regulator issue (bogus altinator maybe).

[Cymrych]

Problem solved. Turns out that "Newly rebuilt" alternator was the problem. 2 amp power drain, gets the alternator nice and hot in about ten minutes without the key ever being turned on. So, back to the store it goes.

Now, if only I can figure out how to get the boots off the inner tie rods...