1994 Taurus GL died on highway

[Celly]

As mentioned on the subject, I have a 1994 Taurus GL 3.8 liter that died on me while driving home, on the highway. Things I noticed before is that the clock was a little dimmer, passenger side window rolled down slower, and the battery light was flickering whenever I stopped at red lights, and moments before it died the Antilock light came on for about 10 seconds then the Check engine came on, acceleration pedal is non responsive by then. When I tried to restart it, it is as if my battery had ran out of juice, jump started it three times but the car would not stay on. I finally had someone to get me a new battery and it worked and drove safely home.

However, yesterday when I came home from work, as I pulled into the
parking spot, similar thing happened, battery light started to flicker, I gave it some gas and it would go off, but a minute later the Antilock light started flickering and about 10 seconds later the Check engine light came on and the engine started to choke, gas pedal non responsive by now.

So I am wondering what could be wrong with my car, I would appreciate any input on what to check, I'm not sure if I gave detail enough description of the problem. The car was appraised $250 at CarMax, so I'm worrying that the cost to have it fixed will be more. I don't have any professional training in car repairs but have enjoying tinkering around and figuring things out in the past. Thanks!

[shorod]

Welcome to the forum!

Sounds like you probably have quite a current draw on your battery. Could be due to a fault in the alternator or some other current draw (low resistance path to ground).

If you have a current meter good for several amps, insert it in series with one of the battery cables. If you don't have a current meter, then you can use a test light in series. The brighter the test light glows, the larger the current draw.

Be sure you have all doors closed, the key out of the ignition, the hood light removed (if equipped), etc.

If you find a large draw, then remove fuses one at a time to see which one causes the draw to reduce.

-Rod

[Celly]

Thank you for helping Rod, so, what am I looking for exactly? is the lightbulb not suppose to glow at all? or am I only looking for the largest current draw and assume that is the culprit?


Pendra

[PTG1212]

I'd have the charging system checked out. I think Autozone will do it for free. I think that's an easy good place to start. Also, if it's the alternator it will fry your new battery. FYI. I sold my 94 Sable 3.8L with blown engine gasket to a dealer for $500 last year.

[Gary1234]

The charge light is not ment to glow when the engine is running.

My guess is ... you need a new alternator. The most common cause of failed alternators is not changing batteries every 5 years.

If you have a volt meter, check the voltage across the battery with the engine at idle ... the voltage should be about 14 volts, if its lower then 13 volts your alternator is not doing its job.

[Celly]

Thanks for all the advice guys, I bought a battery tester that goes into the lighter plug and at first it seems like the alternator isn't charging at all, I tried checking the voltage while removing fuses and the voltage stayed at 11.6-11.8 which is below normal according to the battery tester user guide. Then I had to go out of town for a couple days and when I came back the battery is totally drained, so I'm just wondering if the problem is still a bad alternator? Thanks again for all the help.

[shorod]

Yes, 11.6 to 11.8 is definitely low if the car was running. However, since you were pulling fuses, I'm guessing that you didn't have the car running.

The alternator is only functioning while the car is running. If you are only seeing battery voltage while the car is running, then the alternator is not working properly. A fauly alternator can drain the battery if it has shorted windings, a bad voltage regulator, or shorted rectifier diodes. Likewise, a bad battery can self discharge as well as cause an alternator to fail. If the battery has been completely drained, you may want to consider replacing the alternator and battery at the same time.

-Rod

[Celly]

Yea I didn't have the engine running when doing the fuse pulling test, how do I test the voltage regulator? or the rectifier diodes? not sure what rectifier diodes looks like, I'm assuming those aren't part of the alternator, just trying to make sure before spending money on a replacement alternator, it's the end of the month and am in "I'm freakin broke" mode. Also I just replaced the battery when it died on the highway, if the new battery drained, am I going to have to replace it again? I have a car battery charger at home, would that work? sorry for the million questions and thanks for the help once again

[Selectron]

It isn't a good idea to drain a car battery, but your new battery should be ok again after it has been recharged, and your bench charger at home should take care of that.

The few dollars that you spent on the plug-in voltage tester would have been better spent on a basic multimeter, because it is so much more versatile, but not to worry because you do at least now have a means of monitoring the voltage.

I'd suggest you recharge the battery and then make some voltage checks (see below) and let us know the results. If you would normally remove the battery from the car to recharge it then that's fine, but if you intend leaving it in the vehicle then disconnect the connector from the battery negative terminal before you hook up the charger. Just a quick word on safety - always make the connections at the battery before plugging the charger into the line power socket, and then when the charging cycle is finished, always disconnect the charger from the line power socket before disconnecting at battery - this avoids sparks at the battery terminals, where you will have potentially explosive gases.

These are the voltage checks - there are three of them, to be made after re-installing the freshly-charged battery. The first voltage reading should ideally be taken after the car has been sitting parked overnight, but a voltage reading taken after four hours or so should be ok if that speeds things up a little. And the three voltages are:

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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).

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If you could let us know how that goes, that would give a clearer idea of where the problem is.

[Celly]

Ok, so I recharged my battery to full and plug it in the car and left it overnight and here's the voltage results the next day

Engine Off Voltage: 13.1
Engine running idling: 12.5-12.7
Engine revved: 12.6-12.7

Now there's a time during revving the engine where the voltage meter reads 14.4 but only a couple seconds tops, and tried revving it again and again but meter stays at 12.6-12.7

When I put the gear to drive, battery light comes on and meter stays at 12.5 when I drive around the parking lot.

hope that's enough detail to pin point my problem, can't thank you guys enough for everything hehe

[shorod]

After running the car, shut it off and measure the battery voltage again. Does it remain at 12.5 to 12.7, or does it climb back up to a higher voltage?

It certainly sounds like your alternator is not working properly.

-Rod

[Celly]

Just drove around the parking lot again and shut down the engine, the Voltage is now reading 12.7, I am really hoping that it's the cheaper parts that is faulty, unless the voltage regulator/diodes cost more than a replacement alternator haha

[Selectron]

That's great, thanks, Celly - that tells us quite a lot. As Shorod said, it seems likely that your alternator is faulty - either that or there's a fault in the associated wiring.

At first glance your battery appears to be quite healthy so need to worry about that.

You don't have any excessive current drain when the vehicle is switched off, so that's also good. You don't appear to have any shorts or near-shorts when the ignition is switched on either, because if you did then the battery voltage wouldn't be holding up as well as it is.

What's not so good is that you appear to have no output from the alternator, or if you do then it certainly isn't reaching the battery (except for those brief moments when it rises to 14.4V when revved which, frustratingly, is exactly what the voltage should be). This is where a multimeter would be useful to check for wiring faults, so if you can get access to one then I can suggest some checks - measuring the voltage at the alternator 'B+' and 'A' terminals for a start, but it isn't much use describing those if you don't have a meter.

Having reached the stage where you've verified for sure that no charge current is reaching the battery, you may want to take your alternator to somewhere and have it tested, and then take it from there.

Your vehicle isn't really fit to drive any distance, because the battery will be continually discharging when the engine is running, and when the voltage drops low enough the engine will simply stop without warning, and that could be pretty dangerous if it happened in traffic so I wouldn't even try it. I'd phone around and find somewhere that can do a bench test on the alternator - i.e. test it whilst it's off of the vehicle.

I don't know how far away from an Autozone etc. you might be though, so if you want to make some further tests first and can borrow a multimeter, then let me know.

[Celly]

Yeah it was dangerous when everything stopped working while driving, good thing it was late at night and the highway wasn't busy. Anyway, I bought a cheapo multimeter to try test the alternator. It is a 3.8 EFI engine alternator, I don't know where the B+ and A terminals are, from the front of the car, I see one cable at the almost top of the alternator, another one below it with three wires coming out from the connector, and one bigger cable at the right side/opposite side of the pulley. I've been flipping the manual book around but I can't find what voltage value the connections are suppose to generate... I really appreciate all the advice and help, I may have to finally accept that the alternator is busted after this test hehe

[Selectron]

First, just a few words first on how your alternator works, in basic terms. The alternator rotates when the engine is running, and it generates an AC voltage. AC isn't much use in a car though so that then gets fed into a rectifier, which turns it into a DC voltage (much more useful). The voltage mustn't be allowed to exceed approximately 14.2V because that would eventually overcharge the battery, so the next place it goes to after the rectifier is the voltage regulator, which clamps the upper voltage threshold at around 14.2V - this output voltage is made available at the 'B+' terminal which then connects to, and charges, the battery.

In order for the alternator to generate any output at all, a control current must first be fed to something called the alternator field coil, and the voltage regulator is responsible for that task - it varies the current applied to the field coil in order to achieve a steady 14.2V output. The current which feeds the field coil, via the regulator, enters the alternator assembly via terminal 'A'.

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For the symptom which you have, which is no charging current reaching the battery, my first check would be to check the output voltage at the alternator B+ terminal. With engine idling, that should be somewhere close to 14V. If you do indeed find that, then something has gone open-circuit between the B+ terminal and the battery positive terminal, so you would want to check that path for continuity. I don't have a diagram for the '94, but I believe it's the same as the '95 and my diagram for the '95 shows a 'Fuse Link' in series in that path, so that's one possible failure point, with other possible failure points being the various inline connectors.

If on the other hand you don't have close to 14V but see instead battery voltage (12.6V) or less, then the next thing to check would be the voltage at terminal A. That receives current from the battery to get the whole process started, so you should see 12.6V there (when the alternator is functioning correctly that would rise to 14.2V). If you don't see at least 12.6V at the A terminal then something has gone open-circuit between the battery and A terminal - again there is a fuse link in that path, and that could have failed as also could the various connectors.

They're the two obvious first checks, so if you could take a look and let us know what you find. When measuring the voltage, the meter should be set to an appropriate DC voltage range - probably marked 20V or 40V. The negative (black) meter lead should connect to any convenient ground point - the engine block would be ok, and then probe the terminals with the meter positive (red) lead. Of course the engine will be running so take care not to get anything tangled up in the alternator drive belt!

Here is the wiring diagram for the '95 - the rectifier is internal to the alternator, with the regulator being mounted on the rear. The second diagram is the physical location of the alternator connections. The B+ terminal should have a black/orange wire connected, and the A terminal should have a yellow/white wire connected. Let me know if you don't follow any of that.

Wiring diagram

Alternator connections

P.S. On the wiring diagram, the alternator assembly is everything contained within the square at the bottom, where it says Stator, Field, Regulator, and at the right-hand side of that square you can see the B+ terminal at the top right-hand of the square, with the A terminal further down, between the two S terminals.