dch95

I just replaced a 72 month battery just 26 months after I bought it. It needed frequent jumpstarts and was also leaking at the positive post due to a crack and caused a LOT of corrosion. I was told when I changed it out that the old one was good and something was wrong with the car.

So when I put the battery in, I checked the voltage at idle with all accessories running (A/C, headlights, foglights, stereo turned up, etc.) and the voltage reading at the battery was 12.5. Thats what the battery read before I started the car. I could have swore that even at idle it shoud have read at least 13.25 volts. I then disconnect the negative terminal at idle and the stereo quit, the lights turned yellow and the engine idled rough. Revving up the engine seemed to help out but it was still kind of rough.

I followed the procedures outlined in my FSM and EVERYTHING it told me to do passed the test. Although it did not tell me to do so in one procedure, it said to check the belt which I will do tomorrow.

I guess the question is do you think that those two things I did 2 paragraphs above have any bearing on whether or not the alternator is on it,s way out or do you think that what the book told me is sufficient.

Daniel B. Martin

I expect to see voltage at the battery between a minimum of 13.2 volts to a maximum of 15 volts, depending on engine speed. A reading higher than 15 volts points to a bad voltage regulator. A reading lower than 13.2 could caused by any of several internal alternator defects or a wiring problem. A slipping drive belt usually announces itself with a shrill squeal at engine start-up.

Most auto parts stores offer a no-cost charging system test. This is done with an electronic tester and takes only two minutes. Even though the store employee may be an unskilled person the tester is idiot-proof and trustworthy.

dch95

The only thing that bothers me is that at initial start up, the voltage reads at 13.5 but it consistently drops as the engine get warm dropping below 12 volts at one time. I told the people that rebuild alternators/starters about this so hopefully they can figure it out. BTW I checked out the drive belt and got it within deflection but to no avail. Thanks for responding.

Daniel B. Martin

That's a bad sign.

dch95

Just got the alternator back and they said they could find anything wrong with it. Something else you might find interesting. I just tried something different. I turned off the lights and the voltage goes up above 13.2 but turn them on and drops to 12.5. But the FSM states to rev up to 1500rpms and when I do it goes back where it is supposed to be. Think that this is just how it is going to be?

Also the guy at the shop said that when you pull the negative terminal, that puts a strain on the system and it is not a good way to check out the system.

Something else I,ll say is that when the negative was disconnected, that is when I had a drop below 12 volts. I guess I was missleading in my prior post. Do you agree with the guy as far as that is not a good way to test the system? He had the best opportunity to put it too me but he did not do so.

Thanks again for replying back.

vmok

I think it's better to have a battery connected. In class, they told us the battery acts as a buffer to absorb voltage spikes and drops, and that by simply removing the battery, you could cause electrical problems elsewhere.

How many miles does your car have? What area is your car located? You may want to check the routing of the cables becase as heat goes up, so does resistance. You can try swapping the positive and negative cables. Also check for corosion around the negative/ground strap where it attaches to the body from the car. You may also want to check the ground/negative wire from the engine to the body as well. If you're in a particularly corrosive or hot environment, the wire inside the insulation (that you can't see) of some of these cables could be corroded and the cable bad without you knowing. You may also want to run a terminal brush through the inside of your battery cable connectors. Sometimes the metal is slightly pourous. Also, there obviously isn't a perfect match between the terminal and the cable. Those little imperfections can build up carbon deposits. How? Everytime you start the car or draw lots of power, these little imperfection may produce a small, maybe even invisible arch. Each time this happens, a small amount of carbon may form, eventually becoming and insulator between the terminal and cable. I've had this happen to a car, only to change the battery, and have it happen again a short time later and find out that it wasn't even the battery that was causing problems, but the cable connector/battery post.

You also mentioned as the car warms up, voltage drops, but that could be due to the slower idle causing the alternator to turn slower, and thus producing less output.

The leaking battery post is definitely bad. You mentioned that it was cracked. Keep an eye on this battery. If you see seepage coming out of the battery or fluid coming out not caused by a crack, it could be due to overcharging of the battery, causing the electrolyte to gas up. Contrary to popular belief, lots of freeway driving is harder on a battery city driving. Lots of freeway driving will cause the battery to charge. After it's the charge is full, the continued voltage applied to it from the alternator tends to cause a slightly 'boiling' of the liquid in the battery.

12 volts with all accessories running at idle doesn't sound too bad to me. Many cars have their headlights dim slightly at stop lights. It's been a long time since I took the classes, but if I remember correctly, you should be testing the alternator at speed and not at idle. I could be wrong on that though.

I've had several 4th gen Maximas, and in general, I've found the alternator of the Maximas just barely adequate at idle, and that with the lights on and all accessories, you may be drawing power off of the battery.

Hopefully that helps, at least a little. (Sorry Dan, just my $.02. You still da man!)

Daniel B. Martin

I agree.

I thought that cracked battery had been replaced. If not, get rid of it right away. There is no hope for a battery which has lost physical integrity.

Vmok is on the right track here. Please use an accurate voltmeter to measure voltage drops across every electrical connection. Don't neglect the ground side of the charging circuit. You may find excessive resistance in some unexpected place such as corrosion of a battery cable hidden under the insulation.

Thank you for posting. We need input from everyone! Sometimes I feel uncomfortable about people thinking I know it all, because that simply isn't true. I am a hobbyist, an amateur, a shade-tree mechanic just like many other Maxima.Org members.

dch95

Ok, makes sense to me.

Around 70,000 miles (odometer is broke) and I live in San Antonio.

I,ve heard a little bit of axle grease helps out in this situation.

Check!

Battery has been changed.

Correct about testing at speed. It passed that test.

Daaaaaaammm dude! You have wrote a mouthfull and have saved me from worrying any further! You too Dan. I wan,t to express my gratitude for you two helping me out and putting my mind at ease. Make it this way someday and I,ll buy you some REAL mexican food!

vmok

hehe... no problem.

re: the battery. keep an eye on the NEW battery. if it isn't cracked and appears to be leaking, especially around the vents, you may need to refill it with some distilled water. you don't want the battery to dry out, as the plates need to remain submerged. if it's just a little leaking, this could be caused by lots of freeway/highway driving where the battery charges to it's max then starts boiling slightly. if it's excessive, it could be the regulator as Dan mentioned.

it doesn't appear you live in a very corrosive area, but heat does tend to degrade the insulation on the cables/wires, making 'em not last as long. you can coat your battery terminals and with some axle grease, or there's this spray you can get (under $3.00 a can) at most auto parts stores that seals/protects the terminals.

finally, do clean the inside of the clamp that clamps around the battery post as well as the battery post it itself. not just with a regular brush, but with a terminal brush (with wire bristles.) I usually prefer to use the battery post conditioner which actually has 4 blades and scrapes away at the inside of the clamp with one end and scrapes away at the post at the other end. it should be less than $10 for that tool, and it's good to have around, but seems to work better with domestic cars (especially american cars that use that soft lead type clamp).

Don't worry, drive happy! (btw, my car has the original battery with 131,000+ miles, and it's beginnign to crank really slow, so it's about time for a new battery for me too!)

dch95

Dang dude! This is my 3rd battery! Oh well. Only paid 15 dollars for it......prorated price

Thanks again for your help.

vmok

lol... time to get that die hard gold with no-prorate for 3 years

-V