Battery or alternator? Need to get this fixed today!

[fyton2v]

Ok...

I jumped the truck this morning and it started right up. I used a voltage meter to measure voltage.

When the car is off the voltage out of the battery reads 12.8. With the engine running voltage at the posts = 14.2.

So.. the battery is not taking a charge? It's a diehard from Sears that was tested good (by Sears) 2 weeks ago (see previous thread).

What else could it be if not the battery? That rhymed.

 

[trucruiser]

It look like the alternator is doing it job if you are getting 14.2 at the battery with it running, i would say its the battery a dead cell or you are having a voltage drain somewhere..

 

[soggy60]

From experience w/ Die Hards....

pay too much for a crap battery with a great warranty . . .

I'd swap about every 16 months....free of course....

 

[fyton2v]

What are the chances of a voltage drain on a stock truck with no lights or accesories running?

I'm prepping myself for an argument with Sears. The battery is still under warranty.

 

[dfmorse]

fyton;
First off, how many miles on truck? How long has the battery been in use?

The number that u have for voltage indicate a great system. That said, it is possible the have a tested battery that still will not hold a charge. It is also possible to have a current leak somewhere in the vehicle, i.e., something draining the battery with the engine not running. I have this problem with my '94, but it is not really serious. I have come to the conclusion that my alternator, which is hard wired to the battery, is the possible drain. [alternator diodes]

Here's a test that may help.
After running around town, shut the cruiser down and remove the positive lead to the battery right at the +post. This will leave the battery totally isolated from the alternator and the vehicle electrics. Measure the battery voltage which will read around 12.6 vDC. Record the date, time and voltage on paper so that u don't forget same.

The next morning check the voltage again; hook up the battery and try starting the cruiser.

If it starts like normal this will indicate that the battery is "probably" ok. If it does not roar to life, then battery is suspect.

If Sears will give u a new battery, great. However, u could have a start contact [worn] problem; an alternator brush/ diode problem.

...

 

[Jim_Chow]

I would test the battery under a load. Just because it's putting out 12v+ doesn't mean much. Even a nearly dead battery could give this reading.

 

[fyton2v]

The battery is around 2 years old. The truck is a 2000 with 80K miles.

I was wrong about the 12.8 reading... it's acutally 12.6 with the engine off. So in this situation, running at 12.6 with what I thought is/was a mostly dead battery (the lights in the car still work) what does that tell me?

If the battery has a current output of 12.6v the engine should crank?

 

[trucruiser]

What are the chances of a voltage drain on a stock truck with no lights or accesories running?

I'm prepping myself for an argument with Sears. The battery is still under warranty.

Low probability without any mods.

 

[EdsCruisin]

I recommend you ask for a draw test. Before I had my starter contacts replaced, I had them run a draw test to see if anything was pulling power from the battery when the vehicle was shut down. I had a new battery and it would not start. I'm not sure of the exact procedure, but a draw test should be doable by most mechanics.

A 12v battery may not have enough amps to start the engine, but plenty to run light bulbs and such. It is deceiving.

This leads to a question I was considering - has anybody put an ammeter on their LC? What would be a good model and where would you put it?

Ed

 

[fyton2v]

Sears insists the battery is good. They think I have an electrical problem. Something is stealing power. Damn it.

I'm going to the mechanic.

 

[cary]

Sears insists the battery is good. They think I have an electrical problem. Something is stealing power. Damn it.

I'm going to the mechanic.

Even though you are a condom, I'll help.

Checking the voltage with no load, tells you nothing about the actual condition of the battery (as others have stated). So unless you run an actual load test, don't believe the battery is good.

An easy way to see if the battery is going bad is after you shut the truck off, turn the headlights on, high beams, for 10 minutes, then try to start the truck. This will take the top charge off. If it won't turn over, the battery is bad. If it does, the battery is at least in decent condition.

Did it pass that test, well I'll be, Sears may be right for once. At this point you could also pull the battery and go to Pep boys and ask them to check it.

Ok, so now we are sure the battery is ok, what next. You need to measure current draw. Usually the way to do this is to pull the ground cable and then bridge the connection with your voltmeter set to measure ampage. Make sure everything is off when you do this, anything over 5-15amps of draw when you do this will burn up most volt meters. Look online to see what the draw should be (it will be in milamps, about 100-200mA total). If it is more than this you have a problem somewhere drawing current and you have to start looking, pulling fuses one at a time, etc, to find it.

If this doesn't work, then your fxxxed as you have a problem that a Trojan and Bruin couldn't solve.

 

[mobi-arc]

Just a quick addition...shadetree mechanic's method would be to use a test light instead of a volt-meter. If there's enough current to illuminate the bulb, it's too much draw and needs attention to see what parasitic load is pulling current with the vehicle off.

Scott

Even though you are a condom, I'll help.

Checking the voltage with no load, tells you nothing about the actual condition of the battery (as others have stated). So unless you run an actual load test, don't believe the battery is good.

An easy way to see if the battery is going bad is after you shut the truck off, turn the headlights on, high beams, for 10 minutes, then try to start the truck. This will take the top charge off. If it won't turn over, the battery is bad. If it does, the battery is at least in decent condition.

Did it pass that test, well I'll be, Sears may be right for once. At this point you could also pull the battery and go to Pep boys and ask them to check it.

Ok, so now we are sure the battery is ok, what next. You need to measure current draw. Usually the way to do this is to pull the ground cable and then bridge the connection with your voltmeter set to measure ampage. Make sure everything is off when you do this, anything over 5-15amps of draw when you do this will burn up most volt meters. Look online to see what the draw should be (it will be in milamps, about 100-200mA total). If it is more than this you have a problem somewhere drawing current and you have to start looking, pulling fuses one at a time, etc, to find it.

If this doesn't work, then your fxxxed as you have a problem that a Trojan and Bruin couldn't solve.

 

[fyton2v]

My mechanic called. He said everything checked out fine. Good battery and no unwanted draw. WTF?

I think I'm going to buy a new battery. That way if it breaks again I know something is wrong with my truck and not a stupid DieEasy battery.

Cary,
Thanks for the good info and the laugh.

 

[cary]

It sounds like you need to follow up some of the other posts and check that all your connections are good and tight. I agree that it could still be your battery, it wouldn't be the first time one tests okay and then fails, the fact that charging it and then trying to start the truck hints at that. There have been some threads on the 80 forum about batteries, basically get the duralast or Costco battery, they are significantly cheaper than the Die hard and work fine. I started using Cheap batteries when I lived in Oregon, a $100 would last 5 years, a cheap one $30, 4 years. I know the costco one I bought last year set me back $40 and has a 7 year warranty.

Keep an eye on when the truck won't start, is it only when cold, how long does it have to sit, etc. Out of curiosity, have you replaced your starter contacts? This isn't a normal failure mode for them, but I have seen starter cylinoids go bad where they will work if you give them a lot of power but not with the normal current.


You know, you better not let your alumini association find out you are trying to work on your car, I heard they take diplomas back for that. Of course if you tell them you have a UCLA grad doing the grunt work, they will excuse you.


BTW, for those that don't know, the UCLA USC rivalry is probably one of the friendliest rivalry's in the country. Both schools have a lot of respect for each other, and the largest number of graduate students at UCLA come from USC and vice versa (at least it was that way 15 years ago). I think the thing that both schools have in common is they hate Cal (and I live in Cal country).

 

[fyton2v]

I've never replaced the starter contacts. I still live in SoCal so weather isn't a factor.

At this point here is the only thing I know for certain. Both times this issue has happened the battery was very low and needed charging.

I'm going to be kicked out of my alumni club just for talking to you.

 

[cary]

At this point here is the only thing I know for certain. Both times this issue has happened the battery was very low and needed charging.

That narrows it down. It would then only be a bad battery or excessive draw. The cheaper to try is the new battery first, as the draw could be intermentant. Is it possible you left a dome light on, didn't close the door all the way or something like that?

 

[fyton2v]

Is it possible you left a dome light on, didn't close the door all the way or something like that?

It's my wife's daily driver. Anything is possible , but doing it 2 times in 2 weeks would be very out of the ordinary.

 

[cary]

I don't know if the 100 is like the 80, but I know on my 80 if you don't close the door 100% the dome light will stay on until it is (even overnight). This is different than most newer cars that shut it off after 5-10 minutes.

 

[hoser]

The 100 will shut off it's dome light if left on after a certain amount of time.

 

[fyton2v]

Just a quick update for closure...

Since my mechanic couldn't find anything wrong, yet the battery died again (even though it tested out fine) I decided to replace the battery just for grins.

With the new batt my truck has been up and running for over 3 weeks now.

Conclusion: Never buy a DieHard battery.