Battery warning light

[macuser27]

Hello there,

I have a 1999 Mustang GT and have the battery warning light coming on and off intermittently for the past 3 months or so.

Alternator was replaced 2 years ago and battery less than 1 year ago.

Car starts up and drives just fine and never had any issues until today.

This morning when I went to put the key into the run position, I noticed that all the analog dials swept to the max position and back to zero. Car starts up just fine. I drove it about 1-2 miles and parked.

Came back to the car, key into run position and the dials swept through again. But when I tried to start, the starter clicked and loss all power to the car. No dome lights, no trunk lights, nothing. Like there wasn't a battery in the car.

Popped the hood, and disconnected the negative cable from the battery. I reconnected the negative cable to the battery and the power came back on in the car. Key back in run position, dials sweep and car starts up just fine.

Drove another 1-2 miles and parked for about an hour. Went back to car, key in run position, dials do not sweep and starts up just fine. Drove 3-4 miles and the battery warning light came on for a bit, then went away and came back on again.

From my Google search, I found a lot of people saying to "check the grounds". I really don't know what that means.

Any ideas? Help! Thanks a bunch.

 

[ttocs]

by check the grounds they mean to remove them, clean them and then put them back on nice and tight. It is a common place to check for electrical gremlins or you can end up spending a VERY long time to find out it was the first thing you should have checked.

 

[evilcw311]

Also clean the battery connections. Corrosion can be unseen to the human eye. If you don't have a terminal cleaner then go get one. They are cheap.

Pull clamps off and clean the battery post till they shine, then do the same for the inner ring of the terminals.


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[07GtS197]

I had this exact thing happen with my 02 gt. It turned out to be my battery terminals were both in various stages of corrosion. I replaced the terminals and all has been well ever since. It seems to be a common problem with our cars.

 

[ttocs]

you can clean the terminals with cola/coke/pepsi and as logan said you can get a battery terminal cleaner for $3 even at ace hardware. All you do it slap it on the terminal and twist a few times, then take the wire brush on the other end and run that through the wire ring terminal and twist it a few times to clean it up. Some grease on top of the connections will prevent corrosion later.

 

[g36 monkey]

Yea, some grease meaning smother it in Vaseline!

 

[macuser27]

Thanks for the replies fellas.


I'll start by getting some battery contact cleaner and clean all the contacts and wires. I suspect (or hoping) that the wires are the issue since they are 18 years old. The alternator is 2 years old. The battery (brand new Motorcraft direct from Ford) and battery clamps are 1 year old with no signs of corrosion when I disconnected/reconnected them when I loss power two days ago.


Will post updates to this thread. Thanks again!

 

[ttocs]

I was serious about using cola/coke/soda to clean the terminals. No need to go get something special.

 

[Frank.JD.Perez]

Its gonna blow up

 

[evilcw311]

You won't see the corrosion that we are talking about. It makes a clear film that will cause this exact problem.

The fact that you said you took your negative clamp off then put it back on and it started says that's the first place to start.

That generally shows you have the corrosive layer there cause when you pulled the clamp and put it back on it would have scuffed it a lil.


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[ttocs]

make sure the connections are tight enough you can't wiggle them at all.

 

[96blak54]

Its gonna blow up

....one can rely on Frank to throw in a good comment!

It made me laugh

 

[macuser27]

Its gonna blow up

Hahaha! With the bad luck lately that I've had with this car I wouldn't be surprised if it did.

Anyway, Update.

I took the battery out, cleaned the terminals with battery cleaner and a wire brush. Took the battery clamps off the wires and cleaned that. And also cleaned the wires. Put it all back together and the battery light came back on and off, and on intermittently again.


Went to O'Reilly's and the friendly and helpful counter person went out to the car with me and used their hand-held tester and tested the battery with the car off and then with the car running and their device came back with starter-ok, Alternator-ok but battery bad.


Will head to Ford parts counter on Monday and get them to swap it out under warranty and go from there.

 

[ttocs]

the only way to really check if a battery is bad is to remove it from the car and I would recommend doing that before you just go buy another. Take it out and drop it off at your local parts store and have them charge and test it. Just leave it there for a few hours and then have them test it again in front of you. I say to do it 2 times because I have seen batteries come off the charger and pass the test but then when not hooked up to anything they slowly loose voltage and then will test bad an hour or two later.

 

[evilcw311]

the only way to really check if a battery is bad is to remove it from the car and I would recommend doing that before you just go buy another. Take it out and drop it off at your local parts store and have them charge and test it. Just leave it there for a few hours and then have them test it again in front of you. I say to do it 2 times because I have seen batteries come off the charger and pass the test but then when not hooked up to anything they slowly loose voltage and then will test bad an hour or two later.

If There's a shorted cell it can show good then bad then back and forth. Scott hit it on the head with only way to properly test.


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[macuser27]

Latest update.

Went to get the battery and alternator tested again but this time, out of the car. Both tested twice and both passed each time. Tech recommended checking grounds. ie. follow the battery wires and making sure everything is clean and tight. He said to pay careful attention to the wires going to the engine block and starter/starter solenoid.

So basically back to square one, but at least I can rule out the battery and alternator since they have been tested 3 times now.

Thanks again for all the tips and suggestions thus far. And I did use some dielectric grease on the areas I cleaned to prevent corrosion in the future.

 

[ttocs]

how did he test the battery? Did he take it off the charger and then slap the tester right on it? Like I said I have seen batteries test good right after charge and then drop 2v when not hooked up to anything and then they fail. He is correct to check/clean all your connections.

 

[macuser27]

how did he test the battery? Did he take it off the charger and then slap the tester right on it? Like I said I have seen batteries test good right after charge and then drop 2v when not hooked up to anything and then they fail. He is correct to check/clean all your connections.

I drove about 5 miles from home to O'Reilly's with the battery light coming on and off intermittently. Removed the battery and alternator from my car in their parking lot and brought them in and the tech hooked it up to the tester without charging it. He tested the battery, passed and then tested the alt and that passed. I asked him to test both again. Passed again. I was hoping that he would be compelled to have my parts fail so he can sell me replacements but that was not the case.

So I went home and checked as much wiring as I can in the engine bay and it mostly looks good.


Then I went under the car and checked the ground wire that connects the engine block to the frame and it was extremely rusty on the frame end. I disconnected that wire from the frame and started the car and it did not trigger the battery light. Weird.

 

[96laseredcobra]

Any mo re updates on this? My battery light has been on constant since I got the car. New alternator ect.

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[macuser27]

Any mo re updates on this? My battery light has been on constant since I got the car. New alternator ect.

Not really. My next step is getting Ford to replace the battery since it is still under warranty.

If that does not fix it, then I'll try another alternator. The one I have has a lifetime warranty, but I don't know how I can persuade the store to replace it if it passes their testing each time.

Anyway, I looked up the Owner's Manual about the battery light and here is what is printed: