battery going dead!

[duckman1]

I know, it's been talked about before, but...... Anyway, it's my sons car, 1995 NT talon, he lives over an hour away, so it's hard for me to help much. His battery didn't seem to hold a charge, so his grandfather told him to buy a new battery, again, it won't hold a charge for more than an hour or so when the car is running. His ex-stepfather who is a self pronounced expert, said the alternator was bad, my thoughts also, he "had a buddy" who is an expert at rebuilding alternators. they rebuilt it, and the car still does the same with discharging. Now the kicker, I just spoke with my son, his ex-stepfather said the computer was bad because his reader would not connect with it, but yet he also told my son the alternator reads bad, and is only putting out 11 volts. But.......the reason it's doing so is because the computer is bad. They did tell me earlier that the alternator was bad when they tore it down. I also asked my son what lights came on, on the dash, he said three, the battery, srs, and he couldn't remember the other, but it was not the check engine. Now his mother and stepfather insist the car is junk, that he got screwed when he /me bought it for $3000. with 75,000 miles in near mint condition. I say the guy is a jerk , replace the bad rebuilt alternator, the chance that the computer and alternator going bad at the same time are slim to none.

Any thoughts or advice on the subject? (car issue, not ex stepfather, )

Thanks,

Steve

 

[Eclipse45150]

Well, sounds like a problem I had where my stereo was pullin to many amps and would kil the battery.

One easy way to see if the alternator is bad is to go to autozone or a place like that if it will run and have them test it, the alternator might still need to be replaced, I believe that some but not all can be rebuilt, but do not quote me on that. One other way, some places can hook up the alternator and check it when it is not in the car. I would try that first because many places check it for free. Next check the battery to make sure its not just a bad one, then start talkin voltage regulator, computer and more expensive stuff. In my opinion, from many many past problems, I doubt the comp. would be going bad also, it is probably just reading weird becuase of the inccorect voltage.

With the OBDII prob, check and make sure the trim panel that connects to the side of the radio isnt holding the connector out, it has to be fully in for the meter to read.

I dont know what other help I can offer but atleast its a start for ya.

 

[steve]

Steve,

Have them measure the voltage at the alternator output stud too.
It's so common for people to blow the alternator fuse in the car causing the battery to never charge. I'd have to check the manual to be sure but the turbo and 2.4L cars have a signal from the ECU to turn on/off the charging of the alternator for gas mileage. I'm not sure if the 420A NA car works exactly the same. Perhaps one of our non-turbo wisemen can add some details and advice.

Steve

 

[Old Mitsu Tech]

Being a 420a, may mean its more Chrysler. They are world famous for putting the voltage regulator in the pcm. I'll check my manuals tomorrow and try to report back tomorrow night.

 

[steve]

I just checked the FSM. Your correct, the 420A PCM does the voltage regulation by grounding the F2 pin to turn the field on and turning it off when it senses the battery voltage reaches the target. The F1 pin goes to the MPI/ASD relay to the battery to source the field voltage.

There is a 30A fuse on the ASD relay line and a 120A fuse on the alternator output.

Steve

 

[Old Mitsu Tech]

You are going to love this.

The alternator has 3 wires. A white output wire that goes to the fl1 fuse which is a 120 amp fuse. Check for voltage at both sides of that fuse. You have a red wire off the alternator that goes to the ASD relay and to pin 2 of the pcm. It's black/red at the asd and black/red at the pcm. It goes through the J/c 3 junction. The pcm senses the voltage and grounds the blue wire pin 1 on the pcm which is the control for the field coil in the alternator. Great huh? I would check the red wire for 12 volts and if you don't have it, check fuse fl 4 30 amp fuse in the engine compartment relay box as it feeds the asd relay and the pcm on pin 51 The ignition switch provides power through the j/c3 to pin 14 in the pcm which is blk/wht when the key is in the run position. Check that. Fl 6 fuse is a 30 amp which provides power to the ignition switch but that is probably good since you didn't have a cranking problem. There's a 10 amp fuse called f8 which may be inside the car which provides power to the combination meter. Check that. But in the interest of keeping it simple, check every darn fuse in the car. If you can validate that and have 12 volts at the red field coil wire on the alternator you have either the pcm, asd relay or broken wire as your culprit. Let me know if this helped.

Good Luck

 

[duckman1]

Thanks to all who responded, I will be picking the car up in a couple of days, and hopefully get this figured out. Surely something simple, unless I listen to 'old mitsu tech", ! I will definately use your information in my troubleshooting.

Thanks again,

Steve

 

[Old Mitsu Tech]

I wish it could always be simple and easy. It's not so any more. In trying to cover all the bases and without seeing or hearing the car I have to "blast" all the information at you I can muster in the hopes that in trying these that you find the problem. When I can, I promise to keep it simple. The KISS method usually works, but not always.

Thanks and Good Luck

 

[duckman1]

Your only like 6 hours away or so, i'm sure you could just take a road trip to central Iowa and stop by on your way. Worse case scenerio, I make a road trip, and kidnap you for a day or so, or.......send bus fare?

Steve

 

[duckman1]

UPDATE!!

I got the car home today, drove it 45 miles with the battery light on. Opened the hood to let it cool down, went back out to the shop to get some stuff thinking I would work on it later, and see if the kid had been telling me the truth about no oil usage. I happened to look for the computer, and glanced at the fuse box, when I opened it I noticed the 120amp alternator fuse was blown. Tried to pull the thing out, and it feels really tight. These do just pull out, no tricks or releases? I hate to break something being stupid.

Also I was told to check this fuse, do they blow for age, no reason, or? I'm asking this as to why I was told to check it, like it happens all the time, so a clarification would be awesome. Also would the alternator going bad cause this? As I did mention before, the alternator was just rebuilt and the problem persisted, I'm sure the fuse is one of the main issues now. Please let me know any secrets to it's removal, and I'll go away for a brief time!

Thanks,

Steve

 

[ChrisFlo]

That fuse is screwed in about an inch below the fuse itself. Just unscrew it and it'll pull out.

 

[duckman1]

Thanks Chris, I just found that out about ten minutes ago. Any input about why these go bad?

 

[steve]

Any input about why these go bad?

The most common cause is people working on the engine without disconnecting the battery. Then they drop something and short the positive to the body which blows the fuse. The positive terminal and the B+ output stud on the alternator are suppost to have covers but they are often missing.

Less common is just aging. The fuses carry a lot of current during starting an trying to charge a bad battery and they heat up. Over time that weakens the fuse.

Steve

 

[duckman1]

Thank you Steve! That question has been killing me...! Went to the parts store today, they only went to 100amp, told me to go to True Value Hardware, i just rolled my eyes, and said i would go to the other parts store Monday.

thanks again to all,

Steve

 

[duckman1]

The issue turned out to be the 120amp fuse I was told to check. I found out later that the issues didn't arise until after my son had jumped the vehicle. Now I'm thinking the alternator probably was okay also, just popped the fuse. Anyway, all is fine, and thanks to all who offered help.

Steve

 

[Scrubulum]

As a future reference for all those that read this far. The easiest way to check an alternator is to start the car and while it is running disconnect the battery. If the car stays running, turn the head lights on. If it dies, the alternator is dead. Simple yet effective. Hope it helps someone.

 

[steve]

That method is not considered safe.

When you disconnect the battery you can cause a field collapse in the alternator creating a huge spike on the output which can blow the electronics in the car.

Also, one of the things the battery does is act like a huge capacitor and filter the ripple the alternator generates. With the battery disconnected that gets sent to the electronics.

It's much safer to use a voltmeter and measure the output at idle and under load to see if the alternator is charging.

Steve

 

[Scrubulum]

Actually the headlights will act as said capacitor and handle the extra load. I have never harmed, nor heard of anyone harming, anything by testing the alternator that way. I've done it many times, and my father, whom I learned it from, has more experience with cars than most, if not all, the people on this site. Granted, it is not something you want to do weekly just to check. But if your car is giving you problems and you don't have a multimeter in your trunk (most people don't cary one) then it is a good, safe, check.

 

[steve]

Actually the headlights will act as said capacitor and handle the extra load. I have never harmed, nor heard of anyone harming, anything by testing the alternator that way. I've done it many times, and my father, whom I learned it from, has more experience with cars than most, if not all, the people on this site.

I suggest you do a little reading and then explain to your father that times change and the diagnostic tools we used in the old days don't always carry forward. Try looking through a few of these links and then do a google search on alternator load dump.

I would like you to explain to me how a headlight will act like a capacitor and filter AC ripple.
I'm skeptical but always willing to learn new things.

Steve

http://www.batterystuff.com/tutorial_battery.html#11
http://www.bcae1.com/charging.htm
http://www.sto-p.com/pfp/pfp-transients.htm
http://www.boschusa.com/AutoParts/FAQs/AlternatorsStarters/
under Before I install a new or remanufactured alternator, what should I check?
http://web.media.mit.edu/~nathan/nepal/ghatta/alternator.html
http://www.asashop.org/autoinc/april2005/collision.cfm
http://www.aa1car.com/library/2003/us20310.htm
http://www.fordscorpio.co.uk/electsystemtest.htm
http://www.ehow.com/how_112584_troubleshoot-car-wont.html
http://www.cartalk.com/content/columns/Archive/2003/April/02.html

 

[Scrubulum]

Just because something works doesn't mean it is right. Again I refer back to my last statement. If you are in a pinch and need a quick way to test...
I understand the loads and everything that you are saying but the fact of the matter is that I have used this method on many "modern" cars as have many other people I know. All with no ill effect. I will recommend to anyone to take it to Autozone and get it tested but when in a bind sometimes we need to revert to "hack" method.
enough said. If you want to carry on this conversation start a new thread. We are off the original topic.