I have searched high and low for any information pertaining to my problem but have not found any. I have a 1999 F-150 lariat 4.6, 176K miles.

My battery light started coming on and staying on for about 10 minutes then going out while driving about a month or two ago. I have had a machine hooked up to my battery and the battery and alternator showed as good.

Now the light still comes on and goes off everytime I start my truk and drive. Recently the light will remain on and my battery gauge will start to drop as the light stays on. If the light goes off, the gauge goes back up to normal. If the light stays on, my battery charge slowly drops but recharges overnight.

I replaced the battery and alternator in August of 2007. I am confused because both are showing operating normal.

Should I remove both from my truck and take them in and have them individually tested? I am worried I might get stranded somewhere and need to fix the problem asap.

Any suggestions? Thanks!

 

Since it is an intermitent problem maybe the alternator is starting to go out or there is a loose connection.

 

Id suspect the Alternator,even if its recently been replaced.Depending on where,and what you got has alot to do with it.If it was a reman AND from Autozone,its a no-brainer.
Ive had the best results from name brand stores like NAPA,even theyre remans are fairly reliable.
I have had nothing but problems in the past years with Autozone reman parts..
The other chains fair somewhat better,O-Reileys,and Advanced Auto parts
seem to be reliable.
Of course new units can be defective also...

 

I've had them do as you say the light does. This has always turned out to be a bad diode in the alternator. I've never had one discharge like you say though. It probably is a defective alternator though.

 

Your alternator is going out and getting progressively worse. My Expedition did this and finally left me stranded.

As soon as my F-150 started the same symptoms, I changed the alternator. No issues since.

 

Thanks everyone! I bought the alternator and battery both from Advance Auto. Now I can't find the receipt! AARRGGHHH! I wish they could look you up in their computer. I have not found any loose wires, I was thinking it was a ground problem. Of course the day I started this thread, it ran flawlessly and the light never came on! Figures! I will take my alternator off and up to Advance and swap it out or try for a refund and try Napa.

Thanks for all the advise! You guys rock!

 

I can't tell you how many battery problems I've had with mine.

 

Well the Gremlin remains. I have not had the chance to replace my alternator as I have been dealing with a bad back and sciatic nerve. Anyways, the problem was getting better, battery light coming on for only a few minutes then going out. Yesterday all my gauges started going squirrely while doing 70 down the interstate then they all went dead. They came back on, went off then only the battery gauge was working and it was pegged at H. When I got off the interstate and got on the brakes and lowered the RPM, everything came back, battery light went off and gauge dropped to normal. Light turned green, I pressed the accelerator and the battery gauge pegged and the light came on. On the way home at midnight, same thing and my lights were bright as fire! I must really be pushing some juice through my truck!

I have figured out when I am about 1500 RPM, the battery light is on and guage reads High. When I am under 1500 RPM at idle, it runs fine! All I can think now is what all of you have already said, must be the alternator. I know if I don't fix it soon I will fry my battery too. So, I am asking a friend to help me tomorrow and finally get it changed out.

Just wanted to update you guys in case anyone has the same problems.

 

It will be the alternator. I just put the second one on my truck about 2 months ago.

 

When I replaced my alternator ( it was doing the same thing as yours) it took (3) altenators within a month until NAPA got sick of seeing me and gave me a new Delco for the same price as all the bad ones I kept getting from them. Sounds like the same deal you got going.

 

Got er did! Running great now! The autostore I bought the bad one from swapped it out no receipt, no questions asked. I went to NAPA 1st and bought a brand new one for $192 and change. Came home, neighbor came over and we took old one off. He suggested taking it back to where I got it from but I had no receipt, we tried anyways and they swapped it out no questions asked. Hopefully it will last, if not thank goodness they are a breeze to remove and install! NAPA took back the one I just bought from them and I'm not out any money.....for now.

Thanks again everyone!

 

Another happy ending..... Glad it's fixed.