Tslice

Okay, I have a question about a problem I'm having. I'm not sure, but I believe the digital volt meter readout has never shown the batteries volts to be over 13. But never low enough to get under 11.6 while running (therefore overriding the coolant temp readout), so I never got concerned.

As of a few nights ago, however, it now regularly dips below 11.6v while driving. With the radio on, dash lights bright, head lights on bright, and using the brakes, it is hard to be above 11.5v while going 45mph. The most the volt readout will get to now is 12.5v and thats with no accessories on, in the day, going 50-60mph. Even though it can dip all the way down to 10.7 or so while driving at night with all the stuff going, the car hasn't died while driving, yet. So I know the alternator is doing something (but obviously not keeping up).

I checked the battery water level, just barely low, so I topped off with a little distilled. I went ahead and clipped my battery charger to the battery and charged it on the 6 amp mode overnight. The HIGHEST I've been able
to get it to charge to is 12.5v with the battery charger overnight. Now, keep in mind, this is
with the vettes positive and negative wires still bolted onto the battery terminals. Is this what is
preventing the battery from charging up to say 14v+?? Should I disconnect the wires from the
terminals before attempting to charge it fully???


I went to autozone today to have them test the
battery and the alternator on the car. The guy said his reader said the battery wasn’t good, but that was because the voltage was only at 11.5v. He said I'd need to have the battery fully charged in order to test the battery and the alternator on the car. Is this true? What should I do? Should I try disconnecting the pos. and neg. wires while the battery is still in the car, and see if the battery charges fully and if the problem goes away?? Or should I just remove the battery and the alternator and bring them inside the store to be tested??

What type of problem does this sound like? I was going to do the test where you pull the negative wire off the battery while the cars running and see if the car dies. But I didn't want to f*** anything up. Does anyone know if that would f*** anything up???
Sorry for all the words. I'm just looking for some good advice is all..

84VetteMan205hp

my 84 has been at 10v for the last year and no problems, when i fist got this battery in june the volts were up at 14v but other that that is stays at 10

Tslice

Like, your saying, it is actually at 10v verified by a actual volt meter? Or you mean just the digital display in the dash says it is 10v, but its just an inaccurate reading, and the ACTUAL battery voltage is higher?? Because 10v is a dead battery :P


Anyways, I still haven't fixed my problem, or even diagnosed it fully. First things first, I'm going to clean the terminals with toothbrush, water and baking soda first. Then I'm going to harbor freight to buy this: http://www.harborfreight.com/100-amp...ter-90636.html and then go from there.

Anyone got any advise? My rear end was recently hit, and we fixed it, but I saw that there is a ground for the antenna on the drivers rear of the car . Could this be it??

hitmanpty

The battery. is only use to start the car.. after you start the car. the alternator take over. giving the necesary juice for the car to work.

one you start the car you can take out the battery, and the engine keep runing. if you disconect the battery with the engine running and the engine stop. you have to check your alternator.


you know. I just read some where that is not save to disconect your battery when the engine is running.. so I prefer for you not to do it

Tslice

Haha yea I was going to say, thats not good on the car!! It's funny because most of the mechanical people im friends with have said just to pull the cable from the battery. So it's definitely common knowledge. Just not safe on cars with ECU's.

It started snowing here pretty bad, so its holding me off for now. But I'm going to try cleaning my battery terminals and wires, first. Then I'm going to test the battery and charging system with a reader.

But for now I'm going to be driving my 740 turbo instead, and putting a bible on the hood of the vette to ward off evil gremlins.

Cliff Harris

For a quick check of your battery and charging system, turn on the ignition without starting the engine and check the voltmeter. You are now reading battery voltage. Start the car. You are now reading the alternator voltage.

Keep in mind that there are some voltage drops along the way (like inside the ignition switch, for example). The voltmeter itself may not be accurate.

The alternator output voltage is controlled by the voltage regulator inside the alternator. It also limits the output current. You can replace just the voltage regulator if you think it's bad. There are also several rectifier diodes inside the alternator, some or all of which can go bad. A dirty connection will also affect the output voltage, especially during times when a lot of current is being drawn.

I had an intermittent voltmeter light coming on a while back and I took the alternator apart and put it back together without replacing anything and it has worked fine ever since. I suspect a poor connection somewhere.

Tslice

Right on! That's what I'm looking for. Is there any material around that can assist me in taking off my alternator, taking it apart, and putting it back on? I've done a couple alternators in the past, but never one on a vette.

XILd86z51

First and foremost, please do not pull the negative battery cable with the car running. The alternator uses the load of the battery to regulate some sort of electric voodoo. This "voodoo" will not mix with the bible you placed on the hood and will damage your eternal soul.

The typical automotive lead / acid battery produces 2.1 volts per cell, containing 6 cells (thus the six holes you filled with distilled water), equalling 12.6 volts. If your battery charger gets you to 12.5, you are doing well...so far. The alternator has to produce a voltage higher than that to charge the battery. At or about 14.7 is your goal.

I think that obtaining a voltage meter is your next step. Voltage drop over the battery should be about 12.6v. While the car is cranking, it should not drop below 9.6v. Why 9.6? I don't know, that is what I was taught. If those check out good, test the voltage drop across the alternator. Should be around that 14.7v. (last I checked, mine was 14.3v) Then check the battery again with the car running. There should be no more than a very insignificant difference.

Without being familiar with your car, I would say:

If battery voltage sits about 12.6 and doesn't dip below 9.6 cranking, battery is good.

If voltage drop across alternator and battery are about 14.7 with car running and dash is showing less, dash seems to be malfunctioning or there is a gremlin inhabiting your vehicle. Replace bible on hood.

If voltage drop across alternator and battery is significantly less than 14.7v (i.e. 12.x or less), alternator may be delinquent or preparing to start a union. It may need to be let go and replaced with a more conforming individual.

If voltage drop across alternator is about 14.7v and across battery is much less, you would seem to have wiring / corrosion issues. Clean contacts at alternator, battery and ground and check resistance (ohms).

I am not sure of your existing electrical knowledge (I am no wizard), and didn't mean to insult you if you knew all of this. If it were my car, these are the next steps I would take. If I had a legal department, they would tell me to say that "Prior results do not guarantee a similar outcome." Hope this is helpful as I had fun writing it -Jason

gerardvg

Test the battery with ignition off it should have at least 12.6 volts, then start the car it should be around 13.5 to 14 volts depending on accessory loading. Also note battery's come in varying reserve capacity's you need one to suit your cars electrical load.

The alternator will try and keep the battery between mid 12 volts to mid 13 volts, you should notice a jump in voltage when the car starts. It will be higher at first and then the alternator will cycle the charging as it is charged up.

Also if the battery is being overcharged 14.5+ volts for a long time it will kill it the same as deeply cycling (draining) the battery boiling of the water and buckling the lead plates if quickly drained.

Once a battery cannot maintain 12 volts it will make the alternator seem like it is not charging much.

It is normal for the battery voltage to be around 11.8 to 13.5 during driving depending on the accessory load volts and rpm, with a/c and lights on at long idle especially below 600rpm it may be around 11.8volts and will rise during acceleration to mid 13 volts that is an indication of the capacity of your alternator at various rpm's.

So in short check your battery engine off and if it drops in charge overnight due to internal discharge or a high accessory load, check your alternator performance the volts before starting and the volt rise when you have started your engine.

I get a new company car every 3 years and even brand new cars regularly need a new battery after just one year (crappy cheap ones the car makers tend to use)

Letting a car sit for days or a week at a time will greatly reduce its life span, same for even rapidly discharging a new battery just once greatly decreases its life expectancy.And how well it will maintain electrical loads.

In short the voltage is related to battery acid level (in specific gravity) charge state and alternator charging capacity.

GQ-ROD

On my 84 i had installed a new maxx walmart battery ( good warranty )

My volt guage was reading 15.6 volts and as low as 11.5 volts.

I don't trust stock guage readings so i tested the battery and the alternator with a dvm.

I knew it was the alternator that was bad since i just bought the battery but new batteries can be over charged and individual cells ruined.

I tested it with my DVM and it showed irregular voltage output from the alternator.

Replaced it with an advance auto parts alternator,( got coupon for 50.00 next purchase of 100 or more ).

Guage now shows 13.00 volts min and as high as 13.5 so this is good.

However remember that you will lose 1 volt to resistance in the stock wiring, so my alternator is actually putting out 13.5 to 14.5 which is normal when tested with the dvm.

A simple battery test is have someone start the car while you have your dvm leads attached to the battery if it shows less than 9 volts or less while the engine is cranking the battery is bad !

To test the alternator attach your dvm leads to the battery, it should show 13.0 to 14.5 volts at idle, if it does not it's going bad or is already due for replacement.

Autozone's machine may not reveal that your alternator is bad, they have gone with new machines in order to test alternators for their lifetime warranty coverage which they have denied in the past even though my alternator was INDEED bad. Went to anther autozone and after speaking with a manager they replaced it so watch out for this.

DinoBob

What year is the car?

DinoBob

Duh. It says in the subject. Check the terminal block behind the battery for tight, clean connections.

Tslice

Update:

Did the test with my DMM after charging the battery while the terminals were hooked up. I am unsure how to charge corvette battery (mine is side post version) with the clips on my schumacher smart charger charger WITHOUT having the cables bolted in. I assume I just unbolt them, take the pos and neg cables off the bolts, and then screw the bolts on without the pos and neg cables and then clip the charger onto the bolts?? I dunno. This is my first vehicle I've ever had with side posts...

Anyways..I charged the battery for 1.5 hours and it went from 9.9volts to 12.8 as tested with my DMM. When turned over the battery dipped to 9.8 volts and then went back up to 11.88 volts. While idling I could not get the battery to get above that. While driving I couldn't get the inside display to go above 12.1 volts. And that was with NO accessories on. I found that the inside dash readout is between .3 and .5 volts below what the DMM reads at the battery.

Also, when I hit the brakes, the inside readout will go from 12.1 to 11.5 or less rapidly. With the heater turned on the same thing happens. When the windows get rolled down almost the same loss occurs. Meaning the vehicle can be drived in the daytime with no accessories, but add nighttime onto the equation and you get residual loss. Is this the alternator going bad, connections, or is this due to a short?

GQ-ROD

Check all your connections to ensure they are not corroded or dirty.

But my bet is the alternator is slowly dying !!

The dvm should show a minimum of 12.5 when the battery is fully charged, but more importantly a minimum of 13.0 to 13.5 volts at idle to know the alternator is truly working.

Shouldn't cost more than 95.00 and is easy to replace and gives you peace of mind.

GQ-ROD

Correct !

leesvet

Heres what to do...you are thinkin right.

Go to the battery box and look for a post behind the battery that has several red wires on it. IF you have this, take all those off and clean each with a wire brush until shiney and re-attach. The harness wires are more important than the battery cables as far as performance. Do the same for the wires on the pos side of the battery. One is for the alt voltage regulator that comes from the alt plug in to harness. Next,. unplug the harness connector to the alt and wire brush that to clean the contacts. Take the cable OFF the alt and clean that as well.


If you DO clean all these contacts, you WILL see improvement.
The system is managed by the voltage regulator and how well it detects the drain or load against the system. The dirtier that connection gets, the less it charges because its not reading the voltage regulator accurately.

Tslice

Thanks! I'm going to try and find those connections and clean them! I really need to get that Helms manual for this car. Is anyone around here selling it?

Also I checked all my fuses with my test light and 4 seem to be bad those are:

3 - INST
10 - FP
5 - CRANK
3 - HATCH AUTO'

the # represents the blade fuse #

Would this affect my problem at all, and what effect has not having these fuses working done??

leesvet

possibly. most fuses do more than what the tag says..
The electrical harness of a Corvette is the nervous system of the car. It can cause engine misfiring,. poor performance, no start, sluggishness, any symptom you can think of. Because the system is managed by resistence and constant voltage (5v reference volts) to control systems...these wires and contacts absolutely must stay clean. They don;t over time and that is the single most common reason for poor performance from anything under the hood. Alt, injectors, a/c...everything.

You can buy used sets of the factory manauls (2 books) on fleabay for about $75. I bought a used set that was like a used book from college classes...all kinds of useful notes in the back and along the page spaces.
There are even some there on CD. There is a link around here somewhere for new sets that will be more expensive but new. The older books had the exact color coding as the wires in your car. Newer books are all B&W with words to describe the colors..? makes less than no sense...had to have been "outsourced" like they say when they don;t wanna say they sent it to China for reproduction.

off topic briefly....
Typical flag waving big American corporation that cries for the news cameras but "outsources" all their work...overseas to keep their bottom line in order. Can you say...red-apple? Yep...the hero to the country that Steve Jobs appeared to be, was the biggest customer China ever had in the last couple decades.

You'll see the word "gage" in your FSM when you read it...

Tslice

I guess most people never really think of the scope of things when it comes to how much electrical connections make a difference in their cars. I speak for myself when I say I never really think of that. But owning this vette is getting me to think that way. I'd like to clean up every connection that I can. Would having the FSM help me greatly in finding these connections and cleaning them?

Also, I replaced the four fuses I mentioned, and they still don't work, leading me to believe it is a relay. Is there a relay, by chance, that controls all four of those fuses? Also, I have no idea where the relays are located. Can somebody help me out?

leesvet

THAT is exactly what the FSM will do for you. Detailed description of the part, location, mounting and access. The electrical book shows wire, parts location, and everything needed for elec diagnosis with just a meter & test lite. Most often the FSM will save the owner at least what the book cost...in the first month. We waste 75% of the parts (cash) that we throw at the car because we did not accurately diagnose the problem. The FSM fixes that right up front.