Whitecloud

Ok, could it be the alternator. Can the alternator drain a battery? If so, can I check it with a voltmeter or something, and how do I do that? The battery is three years old and has no power. It will not even start the car after I have run the car awhile. It may be the battery is completely shot? Would like to trouble shoot as much as possible. Any help will be greatly appreciated. Oh yeah it's an 88 coupe.

Sidenote: With the help of this forum I just flushed the radiator fluid, changed both hoses, thermostat, serpentine belt, and refilled. Thanks for all your advice and help along the way. I am a horrible mechanic, but I love working on the Vette, especially with the help I receive from the forum. Just one more job and we'll be ready for summer. WC

emcopet

Go to a good auto parts store, They will test your battery for free and also see if your alternator is charging. I live in Arizona and 3 years is about normal there. The battery plates swell up and touch each other which causes a short. On the west end of the country there is Kragens, auto zone and a lot more. It is either not holding a charge or the alternator is not charging. There are other possibilities yet but this is where to start. Good luck

vetteoz

What are you engine volts on dash showing when engine running?

pletzvet

It could be your battery or it could be that something is drawing a large amount of current in any number of possible places. Yes, you can take the battery to a service centre and have it tested and you can do the same with your alternator (or you can have both tests done in the car, if you can reliably and safely drive the car to the service centre). Alternatively, you can put a charger on the battery (disconnect a battery terminal in your car) - and if the battery takes a charge and holds a charge then you can begin to look for whatever is draining the battery when it is connected. A digital volt meter would be a good investment if you don't have one...

I don't know if your car has sport seats and all the associated toggle switches??? If it does, these toggle switches are known to get dirty and in some cases the switch mechanism falls apart inside and causes a short circuit. Interestingly - this short circuit (which is protected by a mini circuit breaker in my '85) will kill a fully charged battery in less than 3 hours...I know!

good luck - there is always a solution!

C4boy

As mentioned already, test your battery. You'll have to fully charge it before it can be tested. If you can't drive the car, take your charged battery to any service station or parts store and have them load test it. If the battery tests ok then you need to get a good digital ammeter and do a parasitic draw test to see what's draining the battery. Do you have a service manual? Also, even if the battery is bad, you may have something drawing current when the car is off which is what killed it, like pletzvet was explaining.

Whitecloud

I will charge the battery tonight and see if it holds a charge. Then I will drive it to NAPA and have them check the battery and alternator. Then go from there. I'm sure I'll have more questions when I get back. Thanks for the responses.
What do I set the voltmeter on to get my reading. I know it's a dumb question, but as I have said earlier, I am a rookie/wannabe mechanic. Just learnin.

jfb

You should measure the leakage current by removing the neg battery cable and connecting an ammeter between the neg cable and the neg battery post. After the courtesy lights time out, switch down the full scale current on your ammeter and measure the leakage current. GM says leakage should not exceed 50 milliamps. My 87 draws 27 ma. and causes me no problems. The alternator can indeed have leakage current that discharges your battery and a parts place can test for that.
It would be unusual for a battery to self discharge overnight and that cannot be found in a short test, you have to charge the battery up and measure its voltage the next day. The state of charge can be determined by measuring the battery voltage at its terminals. 12.0 volts and below, discharged, charge your battery up with a charger at least overnight. 12.9 volts and higher, fully charged and linear in between.

GREGGPENN

No chance we're talking about the starter here? What's it do? Click, turn over slow, just dim the lights, what?

Whitecloud

I am charging the battery and at 1:00 in the A.M. it is only at 75% and not moving up. If the battery doesn't take a full charge I'm sure that means I need a new one, but could something have caused it to go bad. How do I check for that? I will still get the alternator checked and let you guys know whats up.

Pres712

On my '86 the interior light timer went bad and they stayed on. When I park the car in the garage I never check to see if they go out. One day I had to turn around and go back in the garage and they were still on. Fixed the timer and no more dead battery. Just a thought for you.

jfb

Measure the leakage current, excess leakage current will discharge your battery. Also, letting a discharged battery sit without charging it back up right away causes sulfated plates and this decreases the amp-hour capacity of your battery. Essentially you have a small motorcycle battery which won't supply starter motor current (100+ amps). Also, you cannot charge a battery up very much by jumping a dead battery and letting the engine run for 20 minutes thinking that will charge the battery up. Batteries should always be charged up at least overnight with a battery charger. I recommend you replace your battery AND measure the leakage current. If you don't have a test meter, a VOM, voltmeter, ohmeter, milliammeter, then go to your nearest Harbor Freight and buy one, they sell a digital VOM for $8 and yesterday I got a coupon in the mail for them on sale at $1.99, they are pretty decent meters too.

pcolt94

I can't comment on your specific battery charger but a good battery that is just somewhat discharged should be charged in 2-3 hours (ave).

Aside from a bad battery connection, it sounds like the battery is low if it is cranking slow.

All the leakage information is great. But if you can't start it a short time after you had it running, then it is not charging or the battery is no good. Most of the time a current leakage problem is an overnight situation and may pull the battery down in 5 or 10 hours.

I am lucky to get 3 years out of a battery I have. After 2 years in a hot climate (Orlando) it's only a matter of time till I am getting a new battery. At 3 years the battery definitely may be not good and won't hole a charge.

If you can get it started again, measure the battery voltage when it is running. If you get between 13-14.5 volts, chances are your alternator is charging OK. I would question anything below 13 volts. 14 volts is your real target number and what you looking for.

Complete you profile so we can see where you live and have all the information.

cvett44

Check your cigarette lighter. I had the same frustration on one car, could not figure it out and finally found out there was a penny in the cigarette lighter. Check it out. That is what happened to me.

turbotim23

Have a shop check your charging system first before looking at voltage drains in the car and yes a bad diode in your alternator can drain a battery over time if left sitting for a long time. It happened to me once. Good Luck Tim

rsovine

My 84 is doing the same thing. I replaced the battery and it still goes down. I replaced the alternator and it helped for about six months keeping the gauge up around 14 volts but then it started again last month. It cranks up ok but reads around 9 volts then will charge to 12 and not any more unless I rev the engine. I am ready to pull my hair out on it!

I hope you find out so others may learn.

Whitecloud

So far so good, I charged the battery and took it to NAPA, the guy did a load test and said it was turning out 400 cranking amps for a 550 amp battery. He told me the alternator was producing 13.9 volts which according to this post should be fine.
What do you think about the 400 amps, should I go ahead and replace the battery anyway or is that enough for the summer? Would you do any more tests or wait a week and see how it holds up?

C4boy

You need to do a parasitic draw test using a good digital multimeter and your service manual to find out what is drawing the current which is draining your battery. Wait a week to see what happens and you're going to be back here complaining about another dead battery.

Everyone can give you a 101 different components that will draw excessive current, but until you do the test you're only guessing.

emcopet

I am an old old mechanic. I always eliminate the obvious and then get technical. 400 amps is probably good for a 3 year old battery. The next simple test I would make is to disconnect the one terminal of the battery overnight and see if it is good in the morning. If it is then there are many reasons why there is a drain on the battery. You don,t need to get too technical right now. You did say you were a novice right. Everybody here will get you going. Good luck.

drjimmy

This is perfect to elminate wether it is a drain issue.

If you find it is a drain issue, hook up the ammeter like others have suggested and start pulling fuses until the drain goes down to narrow your search. Then comes the fun part.