Battery or alternator?
Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 959
Likes: 1
From: Plano, Texas
Battery or alternator?
I hate electrical problems; fortunately they don't happen often.
Yesterday, coming home, my car hesitated at a stop light. That is, idle went down to the point of nearly stalling out. I went to a gas station, filled up, got in an heard nothing but a click of the starter. There was not enough juice to turn the motor over.
I called my wife, who brought jumper cables. Jumped it, and it died as soon as I took off the cables. Jumped it again, and it kept running. Going home I noticed the gauge was not quite up to 12 volts; it had always run at 14 or so. My guess is that the car was running off the battery, which finally just gave up because the alternator wasn't charging it sufficiently.
To cut to the chase, is best guess the alternator? Or, the battery? I'm taking the battery now to be checked. It's pretty old. My fingers are crossed it's gone. The alternator doesn't appear to be very difficult to swap out, though. If it makes a difference, it's a '93 model.
Anyway, thanks very much for the input. As always, I very much appreciate your help.
Stephen
Plano, Texas
Yesterday, coming home, my car hesitated at a stop light. That is, idle went down to the point of nearly stalling out. I went to a gas station, filled up, got in an heard nothing but a click of the starter. There was not enough juice to turn the motor over.
I called my wife, who brought jumper cables. Jumped it, and it died as soon as I took off the cables. Jumped it again, and it kept running. Going home I noticed the gauge was not quite up to 12 volts; it had always run at 14 or so. My guess is that the car was running off the battery, which finally just gave up because the alternator wasn't charging it sufficiently.
To cut to the chase, is best guess the alternator? Or, the battery? I'm taking the battery now to be checked. It's pretty old. My fingers are crossed it's gone. The alternator doesn't appear to be very difficult to swap out, though. If it makes a difference, it's a '93 model.
Anyway, thanks very much for the input. As always, I very much appreciate your help.
Stephen
Plano, Texas
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
Jumped it again, and it kept running. Going home I noticed the gauge was not quite up to 12 volts; it had always run at 14 or so. My guess is that the car was running off the battery, which finally just gave up because the alternator wasn't charging it sufficiently.
Also, get a flat blad screwdriver and touch it to the back center of the alternator while the engine is on. If it sticks magnetically, the alternator is working. If not, the alternator is not charging.
Race Director
Joined: Dec 2006
Posts: 10,383
Likes: 4
If you do replace the alt be careful with the plastic clipped on connector on the bottom. I managed to break mine and was fortunate to find the connetor in the HELP isle. Mine had gotten brittle but even so I wasn't ginger with it.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
Likes: 5
From: One day you're a Comet...the next day you're dust... Arkansas
I never guess unless I have to. You are doing the right thing, check the battery first then the alt. It could also be a loose positive cable. The symptoms can be just as you described.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
If the alternator was not charging the battery, the battery symbol light would have been lit on your dash. If not, then you have some other problem, but your low battery voltage indicates the alternator could be defective or you could have a shorted cell in the battery making it a 10 volt battery and heavily loading the alternator dragging its output voltage down. You are doing the right thing by having your battery checked and the next thing is to have your alternator checked. Most parts places can check your alternator in their store and some can check it in your car if you can get it there! 
Burning Brakes
Joined: Dec 2000
Posts: 1,161
Likes: 0
From: Orangeburg, NY
Sounds like an alternator, but you can do some simple steps before going for a new battery and/or alternator. First, check your positive and negative connections on the battery, clean and tighten as necessary. Check the grounds, there should be one on the frame, driver's side near the alternator. Check the connections to the alternator, making sure they are clean and tight. A can of connector cleaner will help. Have the battery checked to make sure you do not have a dead cell.
It appears that the alternator is not putting out. Typically, if the car is running and you remove a connection to the battery (not recommended) the car should continue to run. If it stalls, it indicates the alternator is not putting out, thus causing the car to run on the battery and thereby draining it.
Many auto parts stores will test the alternator for free.
It appears that the alternator is not putting out. Typically, if the car is running and you remove a connection to the battery (not recommended) the car should continue to run. If it stalls, it indicates the alternator is not putting out, thus causing the car to run on the battery and thereby draining it.
Many auto parts stores will test the alternator for free.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
Likes: 508
From: South-central Missouri
Yep!
If the alternator was not charging the battery, the battery symbol light would have been lit on your dash. If not, then you have some other problem, but your low battery voltage indicates the alternator could be defective or you could have a shorted cell in the battery making it a 10 volt battery and heavily loading the alternator dragging its output voltage down. You are doing the right thing by having your battery checked and the next thing is to have your alternator checked. Most parts places can check your alternator in their store and some can check it in your car if you can get it there!
I agree w/ you on every point, being of the electronic persuasion most of my life.
P.
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Thread Starter
Burning Brakes
Joined: Jan 2001
Posts: 959
Likes: 1
From: Plano, Texas
Thanks, everyone,for all the assistance! It turned out to be the alternator. However, I was pleasantly pleased that a rebuilt alternator (with lifetime warranty) was only $100 at O'Reilly's.
That said, 94Z07 was 100% right about the plastic connector. I wasn't careful enough in removing it - the one at the back, and bottom that brings the wires from the harness to the alternator. I broke mine. The replacement from a dealer was $62 - nearly as much as the alterntor. Moral is, be very careful in removal, particularly if it's as brittle as mine was. The replacement, by the way, came with one foot of connecting wire to splice to the original wires. Not difficult to do, but time consuming to do correctly.
Again, thanks very much for pointing me in the correct direction. For those curious, the car in my avatar is not the one that had the problem. I have a thing about '93's. The problem was on my coupe.
Stephen
Plano, Texas
That said, 94Z07 was 100% right about the plastic connector. I wasn't careful enough in removing it - the one at the back, and bottom that brings the wires from the harness to the alternator. I broke mine. The replacement from a dealer was $62 - nearly as much as the alterntor. Moral is, be very careful in removal, particularly if it's as brittle as mine was. The replacement, by the way, came with one foot of connecting wire to splice to the original wires. Not difficult to do, but time consuming to do correctly.
Again, thanks very much for pointing me in the correct direction. For those curious, the car in my avatar is not the one that had the problem. I have a thing about '93's. The problem was on my coupe.
Stephen
Plano, Texas
Racer
Joined: Jan 2006
Posts: 473
Likes: 7
From: Houston Texas
Glad you got her back up and running.
I had the O'Riley's GM rebuilds lifetime warranty on for a long time-a few years at a time. The first one lasted about a year then the 2nd and 3rd seemed longer.
Keep the receipt in the car and the wrenches in the bins behind the seats!
Just in case!
Just my luck they always fail in the hot, humid Houston summer and I even had to change it out in the auto parts parking lot one time!
Good luck!
I had the O'Riley's GM rebuilds lifetime warranty on for a long time-a few years at a time. The first one lasted about a year then the 2nd and 3rd seemed longer.
Keep the receipt in the car and the wrenches in the bins behind the seats!
Just in case!
Just my luck they always fail in the hot, humid Houston summer and I even had to change it out in the auto parts parking lot one time!
Good luck!