Battery good, Alternator good, Buick still dies

[Guest Ansis42]

I am having an interesting problem with my 1980 Buick LeSabre. 4.9L 301. 

 

I have just gotten my Buick back on the road after tearing apart the engine to replace the Head Gaskets. I also had to replace the starter and the battery. The new battery sat unused for a while, and eventually lost it's charge. 

 

The Buick would not start because of the low battery. So I attempted a jump start, and it started right up. However, a few seconds after I took the jumper cables off the battery in the Buick, the engine died. I tried this a couple more times. Each time, the engine died seconds after taking off the jumper cables. 

 

So, I took the battery into Advanced Auto. They charged it up for me. While I was there, I decided to have the alternator tested. They said the alternator was just fine. 

 

After the battery was fully charged, I was able to consistently start the engine. Each day, I would start it up, and simply drive it around my neighborhood for a few minutes (I wasn't brave enough to take it out on the open road, for fear of it dying). 

 

In hindsight, each time I started the engine, it seemed to crank a little bit slower than before. I didn't think anything of it at the time.

 

However, one night, I decided to nut-up and take it down to the gas station to fill it up. I put gas in it, tried to start it up......nothing. It cranked VERY slowly, and never started. 

 

I had to have my girlfriend come give me a jump. The Buick started up, but on the way home, I could tell the power was slowly fading. When I got home, I turned the engine off, then immediately tried starting it again. As I expected, it gave a slow crank, but did not start. 

 

So, normally I would think this is caused by a bad alternator. However, they tested it and said it was fine. Should I take the alternator to another place for a second opinion? Or maybe see if there is a problem with the wires connecting the alternator to the battery?

 

Thank you for any help you can provide.   

[Pete Phillips]

Check all ends of the battery cables and alternator wires for corrosion that may be preventing the alternator from charging up the battery when car is running. I had the same problem on an old Mercedes 240-D and that was the reason. I realize the two cars are very different, but charging systems are the same, regardless.

Pete Phillips, BCA #7338

[avgwarhawk]

I can see the alt bench testing as good.  However, when installed in the car is the wiring clean and tight?  Do you have a volt meter that can be used to see if the battery is getting a charge.   There is no doubt the battery is slowly dying and the car not running.  However, the dash light for the alt is not no correct?  

[Mudbone]

The best way to test a charging system is with the alternator in the car. Check voltage before starting. Check voltage with the engine running. Then turn on the headlights A/C etc. If the alternator is working correctly it should read 13.5-14.5 Volts. You may have a wiring issue. Mud

Edited May 27, 2015 by Mudbone (see edit history)

[NTX5467]

It can be a battery cable that's got an internal problem, which is not visible.  Check each cable for resistance and continuity.  When you get the engine running, ALSO check battery voltage with the voltmeter.  First check between the battery terminals (which should be about 14 volts when the engine is running.  Then with the engine still running, check from the + terminal and various items on the engine (alternator case, an intake manifold bolt or other exposed metallic bolt/stud with no paint on it, for example).  The voltage should be the same as between the two battery terminals.  If not, there's probably something awry with the battery cables (try the ground cable first).  ALSO ensure that EACH of the battery terminals and cable connections are completely free of any "gunk" as even a little can decrease "on the car" alternator output by about 10%.

 

Although the bench checks are good, the best thing is an "on the car load test" of the charging system.  That way, you see what's really happening with the total system.  You might need to take the car to a GM dealer or a quality repair shop for this (so you can expect them to have quality diagnostic equipment, rather than otherwise). 

 

Depending upon how long the battery has been dormant, it can be somewhat sulphated internally.  This can affect how it "takes a charge".  Might also have another internal issue that's just starting to appear.  When I put a battery on a self-regulating charger, a battery that's in good internal condition will usually come back to a lower charge rate as time progresses.  If it's good internally, when it gets fully-charged, the needle will bounce off of the "0" mark on the indicator gauge.  If it's getting some age on it, it will linger longer in the "5 amp" area and might not get to the bounce routine until hours later, if at all.

 

Please advise of your progress,

NTX5467

[VickyBlue]

I had a "situation" a couple of months ago, as long as the battery was on the charger, the 56 started fine. Leave it off the charger for a week and a half and it the battery would drain down to nothing. Parasitic Drain. Once the battery was full, I removed the negative battery cable and connected my multi meter, black to the negative battery post, red to the negative battery cable. It read 5.5 Amp. They recommend you should see no more that 30mA or 0,030A. I removed all the fuses, I think 5 or 6 and it went down to 0. I put them back in one at a time and it was traced to the stereo. I had, by accident put the power on lead wire to the hot battery bus. After moving it to the key-on power bus, problem fixed. 

[NTX5467]

Many modern radios, especially those with internal clocks, need a constant battery voltage to keep that process ongoing.  On Delco radios, this was the brown wire, as I recall.  Some seem to also need a power feed "live" for their amps, too, even when turned off.  Good diagnostics!

 

NTX5467

[old-tank]

The best way to test a charging system is with the alternator in the car. Check voltage before starting. Check voltage with the engine running. Then turn on the headlights A/C etc. If the alternator is working correctly it should read 13.5-14.5 Volts. You may have a wiring issue. Mud

Also some alternators need the engine to be revved to start charging.

Some batteries, when completely depleted, will never recover...

[buick man]

…. or you have a massive short which is draining the battery.  Charge the battery up and have it tested to verify it is good to go.  Install it in your car and start it checking the amps going into the battery.  If O.K., then turn it off and let it sit for a few days then try and start the car.  If you have an internal short it will have drained the battery and you will have found a possible culprit.  Also the internal windings of the starter could mimic  a poor battery upon the need to start once it is warm up like at the gas station episode you elude to.  If DOA at the gas station did you check to see if you had head lights or interior lights.  Did the head lights dim drastically upon tring to start the car or did they stay on without or little diming when attempting to start the car?  

Edited June 1, 2015 by buick man (see edit history)

[NTX5467]

Once upon a time . . . I had a car that if driven daily, would operate just fine, but if I let it sit about a week, the battery would be dead.  I got a friend to warranty the battery, which also gave me a new "known quantity" in that area, but same thing.  I started unhooking the ground cable from the battery when I parked it and everything was good. 

 

One night, in an empty shop, I attached the cable to the battery post.  There was a faint spark.  I heard a faint "chingggg". I left it unplugged again, with the same result.  The only thing that made that type of sound was the alarm module under the front edge of the instrument panel.  I found it and unplugged it, battery drain issue solved (no more faint spark when attaching the cable, either).  No more other "chings" or sounds after that, but a solidly reliable electrical system.  In this case, the car was a 1980 Chrysler Newport, but the same thing could be happening on ANY vehicle with a chime module from that era.

 

NTX5467

[Guest Blackpack]

I had these exact same symptoms last summer on my 65 Thunderbird. I spent the entire summer tracing wiring, replacing batteries, replacing alternators, etc, etc. Then I decided to try and replace the voltage regulator. Not sure if you have one on your car, but that was the problem all along. Ended up being a $23.00 part