Hi all,

I have a 1998 F150 with about 110K miles. I have no problem starting and it seems to run OK, but the battery drains quickly once started. Once drained, all the the gauges go dead and it eventually stalls.

I replaced the alternator, but it was no help. Once I recharge the battery, it seems to hold the charge until I start the truck. Once started, it drains quickly (you can actually watch the battery gauge indicator go down).

Anybody have any ideas? If you can't tell, I don't have a lot of experience at this. Any help greatly appreciated.

 

Even though you just replaced the alternator, Check to see if its hooked up properly. Sounds like it is not charging. Isnt there a fusible link on the + side of the alt.?

 

I had the help of somebody who was experienced when I replaced the alternator, and there did not seem like much that we could have done wrong. The battery seems to drain very quickly, even when there are nothing in use (such as the lights, radio, etc.). It seems more like some sort of short to me, but I'm not sure how to approach it.

 

How quickly? The high power computer ignition systems will drain a battery quickly if the alternator is not helping. I dont know if this little trick still works on newer cars, but if you start it and disconnect the battery, and it dies, than the alternator is not working.

 

Bad advice! DO NOT do this on a computer controlled vehicle unless you enjoy shelling out big bucks for blown electrical components. The battery acts as a filter and keeps the alternator output in check. If the battery is not there, the alternator can run wild and produce very high voltage that electronic components can't handle.
Do you know if the truck has the original battery in it? You may have a shorted cell in the battery. Good luck!

 

I agree, so does FORD. Never "disconnect the battery" when the motor is running.

The safe "little trick" to check to see if "the alternator is not working" is to leave the headlights on for several minutes to be certain there's been enough drain to demand charging & get a volt reading using a VOM on the connected battery terminals, then start the motor & rev to 2000-2500 RPM & observe what the voltage does. If it does not increase to 14-15 volts a red flag should go up.

Keep in mind that many batterys go bad in such a way that they resist charging, fooling the charging circuit that they're fully charged when they are not. They used to call it 'Surface Charged'. A bad connection in the charging circuit can do the same. Also read a lot of complaints about reman alternators being dead out of the box.

 

Keep in mind that many batterys go bad in such a way that they resist charging, fooling the charging circuit that they're fully charged when they are not. They used to call it 'Surface Charged'. A bad connection in the charging circuit can do the same. Also read a lot of complaints about reman alternators being dead out of the box.[/QUOTE]

I've had that happen a bunch of times.........never trust a battery if you are having electrical problems.........have the battery load checked right away...

 

If the alternator is working, the truck should not stall. There is a chance that you bought a bad new starter. I have had that happen before. If you test the battery without the engine running it should read around 11.5 to 12 volts. After starting it it should read between 13.5 to 14.5 volts. That is a pretty good indication that the alternator is working. It sounds like to me it is still an alternator problem. Make sure you have battery voltage at the back of the alternator on the large wire. If you don't you could have a break between the battery and alternator. Perhaps a fuseable link. I am not for certain these have a fuseable link between the two.

 

Replaced my alternator with a reman yesterday and I went back to the place where it was purchsed to get it tested to make sure it was "good". It is good advise and it takes just a little time out of your day.

 

If you worry a reman alternator might be bad right out of the box AND don't like my advice on how to check the voltage to test for alternator output at home, after its installed, why not have the "place" test it before you even buy it, install it, or make the trip home & save yourself "just a little time out of your day"?


The testers used in my local parts stores require the alternator to be in hand & should be happy to demonstrate their reman for you before you leave the store, eliminating the possibility of a DOA alternator. This way when you install the reman, if it doesn't charge, you pretty well know the problem is in your vehicle.

I learned long ago, the hard way, to bring the old item to the store to be certain it matched the replacement. The last reman alternator I installed was put on the test rig as store SOP. Apparently they'd suffered a rash of defective units!

 

Yes we all know you should have it tested before you leave the the place which is exactly what I did....

Why don't you settle down and think about it for a second.......you have to bring back the old one for your core charge deposit refund anyways. Would it hurt to get it tested AFTER you install just to make sure everything is hunky dory?

EDITED for useless badgering

 

Hi I am new to this forum and wondered if anyone had a copy of the wiring diagrams for the whole electrical system of a ford F150??? I have searched everywhere and can't find them for free...I can't justify paying for that. If anyone has them that would be great if you could send me a copy.
Thank you
Tracker94

 

Check the ALT fuse in the power distribution box under the hood. It may be blown.

 

Try this link...awesome website that another member turned us onto....user and passw. is library

http://www.bedlib.org/ebsco.html

 

Thanks Phillip, That is an awesome site it will be very useful and helpful. Much appreciated. If you know of any other good sites let me know that would be great.
Tracker94