[PeteC]

Car is a Nissan Sentra B15, 2001, with a 1.8L engine.

Last Thursday I was driving home from work when the batter and hand-brake lights lit up. The car was driving ok, but I played safe and didn't drive it on Friday.

On Saturday, after checking out this forum, I changed the alternator. O'Reilly said that it checked out OK and so did the battery, but we changed it anyway.

Battery was showing about 13.5V, alternator was putting out about 14.2V.

Went for a test drive - all OK. Went to pick up son from college, and after about 25 miles the airbag light started flashing, together with the 'O/D Off' light. Car didn't want to go more than 60mph, and got slower and slower, until it stalled altogether about 2 miles from home.

Towed it home, and checked the battery - about 11.5V. Jump started it, and it was fine.

On Sunday I thought it was the grounds, so I hunted down all the grounds in the engine compartment, took them off and ground off any corrosion until I had bright shiny metal on each of the mounting point, the tail and the bolt (found 5 grounds - one near the battery, connecting battery->chassis->engine (a big one), two on the rocker cover (little connections), one by the alternator to the front of the engine, and one behind the washer bottle. FSM didn't indicate any others.

Went for a test drive. At one point, accelerating hard, the battery and hand-brake lights flashed on for a millisecond. Got 9 miles, and had the same situation again; airbag light and 'O/D Off' light started flashing, engine lost all power (luckily I was pulling into my garage when it happened). Checked battery, it was about 11.6V. Left it for an hour or so, and battery was up to 12.3V (dunno why). I was able to start it for the 10ft drive to the end of the garage.

There are no check-engine lights on. Even so, I put a code reader on it to verify - there are no codes being tripped.

I did think it may be the battery (despite Oreilly saying it was good) - but if so, surely the car would still drive once it was moving, because the alternator would be supplying the current? Or am I wrong? Don't want to throw another $100 at it unless it will cure the issue.

I'm at a loss. Any ideas on what it could be, or what else I can check?

Thanks in advance,

Pete.

 

[i68k]

if your battery was at 13.5V, it is probably bad, unless that was a typo of course what was the amperage that they tested? if your alternator is generating <1V, usually its bad, or needs to be rebuilt/replaced. the battery shouldnt fluctuated that much in short time, unless its being used or charging or something.

however, if your battery&alternator are supplying some power, then your ecu should be storing some codes as well. so i wouldnt leave that out of the question, but the ecu will only lose codes if it loses power during operation or it failed.

 

[PeteC]

Thanks for replying. Here are the exact voltages (didn't give them before, as my notes were at home). I don't have any amperages, though.

When measuring 'No Load', I had the engine running, but all car electrics off. 'Full Load' - Car fan on 4, lights on, rear window heater on, car stereo on.

I measured the battery by putting a meter on positive and negative terminals. I measured the alternator by putting the positive probe on the positive connector on the alternator (covered by the red rubber), and the negative on the negative side of the battery.

Before new alternator installed:
-----------------------------------
Battery
Full Load 13.83 No Load 13.76 Car switched off 13.87
Alternator
Full Load 13.02 No Load 13.96 Car switched off 14.12

After new alternator installed:
----------------------------------
Battery
Full Load 14.14 No Load 14.34 Car switched off 12.94
Alternator
Full Load 14.33 No load 14.46 Off (No notes on this one)


Does this give any more help? I can get the battery tested again at a different place this evening - is there anything special I should ask them?

Thanks!

Pete.

 

[ten-sec Spec]

sounds like you have an ignition hot with the terminals shorting somewhere... is there a penny stuck in your cigarette lighter or something of that nature?

 

[PeteC]

Hmm... Didn't think of a short in the system.

I've just checked both cigarette lighters - nothing in either. If there were a hot circuit, how could I check for it? All I can think of is to check resistance when the ignition is off - should be infinite, and if it's zero there's a short somewhere. Any other common areas for shorts to happen in this car?

Thanks!

Pete.

p.s I've just thought... if there is a short somewhere, would that actually stop the car? I'd expect it to drain the battery, but surely the alternator supplies all the electricity when you're driving? I may be wrong... I often am...

 

[ten-sec Spec]

you'd have to test each circuit individually with a multimeter.
i just thought of a penny in the lighter because i had one jump into there from my ashtray once and it blew the fuse. if someone had replaced the fuse with a piece of wire (i've seen it done) it could short out when ignition is on.

try idling your engine and disconnecting the battery while it is running and you will have you answer of whether the alternator is enough to power it alone.

 

[PeteC]

try idling your engine and disconnecting the battery while it is running and you will have you answer of whether the alternator is enough to power it alone.

Yes - disconnected the live terminal when it was idling, and the car continued to run quite happily (left it on for about 10 minutes). Alternator was pushing out 14.2V, even when I turned on the lights, rear screen, blower, air con and radio.

I'm happy to test each individual circuit if I need to (otherwise I've got a massive ornament in the garage). How would I do that? I'm OK with electrics in general, just not on cars.

 

[PeteC]

No evidence of any live shorts that I can find yet...

Yesterday I monitored voltage while I was driving the car (I made a connector for the cigarette lighter to my multimeter).

Starting off I was getting a solid 14.2V, but after about 4 miles it started showing me battery voltage only - 12.8V, which then gradually dropped as I was driving.

I expect the alternator to give a solid 14.2V at all times - correct? If so, then it looks like the two pin connector on the alternator is inconsistent, and only making occasional connection.

So, it looks like todays job may be to nip off that connector and replace it with a couple of spade wire connectors.

 

[ten-sec Spec]

hmmmmmm

nothing's ever easy...

 

[i68k]

did you ever replace your battery? the battery can deny the charge coming from the alternator and give you a dropping voltage while driving. the alternator should give you a fairly constant voltage, but the voltage of the system as a whole depends on the battery releasing that charge. remember, the battery is 12v to the alternator 2-3v increase, the battery is the majority of your voltage readings.

in post #3
you can see your voltages got better after your new alternator, but your voltages are fluctuating when the car is off. with your new alternator, youre getting 14.34 motor on, and 12.94 motor off, which is only a 1.4v increase. so it may be that the battery is gradually eating ~.5v, unless of course you have other wiring/connection/short/grounding issues somewhere.

btw, you dont need to check voltage at the alternator just check it at the battery terminals, with motor off and on of course.

 

[jacjm]

did you ever resolve this issue ??

 

[PeteC]

Sorry! For some reason I didn't get any more notifications of this thread!

Anyway; Yes, I solved it.

It wasn't the battery. I swapped it with the battery out of my Subaru (6 mtgs old), and the symptoms didn't change; a good score in the garage (14.2V), but when driving it the battery would run down.

It wasn't the connector. I did remove the connector and replace it with spades, but the problem reoccurred.

So, what was it?

The (insert cuss words here) O'Reilly alternator.

The brown connector housing was broken. Push it to the left (and this is the housing, not the connector), and it works. It will even stay there for a bit. Push it to the right, and it stopped working.

So, I pulled it out, took it back and replaced it. However, the replacement alternator was giving out far too much voltage - nearly 16V - causing the car to show a charging issue (with very bright lights!).

Took that back for a replacement. Had them bench-test the replacement in the shop - all looked good - and put it in. Drove it for a few days with my Heath-Robinson multimeter set up, and all the voltages look great. Problem solved!

So, at the end of it I know two things;

1. Always get an alternator checked. Even if it's straight from the store.
2. How to change an alternator in less than an hour. I've had the practice....

 

[jacjm]

good for you!!,,,and thanks for posting the answer to this, so that it may help others,,,too many times people on forums like this fix THEIR problem, but never post back with the "final fix".

 

[ten-sec Spec]

interesting to hear. I recently had a defective alternator from autozone... no symptoms like you describe just noises that were wayyyyyy wrong

 

[NolightOff]

Hi,
I recently had an issue with my alternator and am writing this in case it helps someone out as this forum has been great in helping me as well.

My issue was: While driving home at night my lights were real dim an then the airbag light started flashing and the Overdrive started to turn off.

Barely made it home, checked the battery with the voltmeter and it clearly wasn't charging so no brainer right? Need a new alternator huh?

Well I ordered a new one as I've had bad experiences with rebuilt ones in the past and put it in. Start the car and still not charging!! Ugh :/

Then I found a wiring diagram online and the plug that goes to the alternator. (The one with 2 wires) 1 green wire and one yellow/red wire.
Well, the yellow and red wire needed to have power to it, verified by a test light and it had nothing. Checked all the fuses and since they were all good I figured the wire was cut somewhere. I traced it from the relay/fuse box in the engine bay to about the middle of the bottom of the front bumper where I ford it to have corroded and broke. Patched it up and problem fixed. 50 cents worth of wire and sodder.

In conclusion, you replaced your battery and your alternator and still not charging: check the wires, check the fuses and the connection to the alternator.