Here's the situation, I've been having my battery and brake light come on if the car is running at low rpms and with the lights on or even at high rpms by simply turning the defroster on.
Now normally, battery and brake light on would indicate an alternator going bad and this would be your "oh sh** moment where you'd go scrambling to your local shop for an alternator since you have at best, two weeks. This is where I tell you this initially happened 3 months ago. Yeah, got me too! I even bought a new alternator that's been sitting in the car since I have not had to use it. I had the car checked out at Sears since they had replaced my battery 3 months before this. They even gave me another new battery just in case and checked the alternator system and....nothing! I even got one of those grounding kits and still nothing. Light still comes on, its like I'm doing a roll call and its like " yeah, I'm still here". Aggravating to say the least.

What's this about? By the way, the alternator is 2 yrs old.

 

Is the GND strap from battery to chassis and engine good? 12V wire from battery to fuse box good?

Any work done on the car just before this happened?

 

Well, the initial problem had been the rpms dropping when slowing down to the point where it would almost stall and this would ofcourse cause the brake and battery light to come on . Cleaned out the IAC valve and TB- this fixed the rpms but that was it...

The battery wires are in good condition...both of them..

 

Good fuel rail pressure and no ECU codes otherwise? After your work, did you disconnect power to reset the ECU?

 

Give us some real information. How old is the battery. What is the voltage when supposedly charging at tickover.

 

Reset the ECU right after the cleaning. Fuel rail pressure? Would this throw off a code?- The car is running perfectly fine otherwise..

 

Battery is three months old, the one replaced before that by Sears just for the heck of it was maybe 6 months old. They replaced it just to make sure it wasn't the battery

Voltage- Now, its a fairly new battery that was tested under the conditions I mentioned and battery was confirmed to be o.k and nothing has changed since then so I would assume this is o.k. Only thing they mentioned was that they noticed a slight discharge on the system (thus the battery/ brake lights).

I'm curious, where are you headed with the voltage thing? I dont have any dimming lights or anything like that at all...

 

Low fuel pressure would not throw a code. Is the idle speed correct? 650+/-50 RPM in neutral for auto and 575+/-50 RPM for manual tranny.

 

Because without knowing the voltage while the motor is running we have no idea what the alternator is doing. Knowledge = Power, you know... replacing a 6 month old battery "just to make sure" is the act of a dumbass with more money than brains, glad I am not an owner of stock in Sears... there are simple cheap devices for testing batteries.

 

yeah man. Idle speed is good right about 625 (its a manual)...

 

thats funny man! I'll get some readings as soon as I get off from work and post then...any other thoughts in the mean time?

 

well. i reviewed the symptoms one more time.
and i put them together with my own experiences with Sears(tm) automotive products.
and I conclude that whatever Sears might think, your alternator is toast.

 

hmm, I just got the voltage readings and while the motor's running its at 14.8V at the battery....

 

Battery and Brake Light on at the same time means low voltage or a bad alternator. Ive had one put out correct voltage while idling and the fluster and and the light at different rpms. If yours is only doing this on low rpms I would recheck the obvious. The slack in your alternator belt, the ground on your battery, and corrision at the terminal clip on the alternator. I am willing to bet money on the alternator despite your readings. You sound like you know what your doing, youve done your basic troubleshooting, and you have a new alternator. What are you waiting for?

 

I have checked everything else with the exception of the terminal clip at the alternator. I'll check that.

what am I waiting for? I hate not knowing exactly what it is; a bad alternator is not supposed to last 3 months.... Mainly though- its too cold and I dont want to go out and do this then have that darned light come on again I mean, who has had a bad alternator last months? Seriously?

Anyway, what's that old adage-if it walks like a duck....I'll suck up and just change the alternator during the week. I'll post back and let you know how it goes...thanks guys..

 

Im not sure where exactly you got your alternator from but regular autoparts stores offer lifetime warranty on thier alternators and thier starters. Its not uncommon for remanufacured alternators to die after only a few months They usually replaced only the failed diode or regulator inside the alternator and then respray / resell it. Other tests you can preform are pulling you positive battery terminal while the car is running and your dummy light is on. The car should continue to run fine of the power of the alternator if its starts to cough or die its just more evidence for your case.

 

The alternator on it now was installed by a local mech when I was in a bit of a hurry so....

I'm not sure if I tried the pull the positive terminal yet although I pulled one of those a few weeks ago and the car ran fine. I'll try that before replacing the alternator to see what happens.

 

what are these voltages

(with the engine turned off)
1) between terminals with NO wires hooked up
2) between terminals with wires hooked
3) between power bus side on fuse block and chassis
4) between terminals with the engine at idle (or lowest running speed)

IMHO if alternator (&belt) and fuel rail checks out then there has to be something else causing voltage drain (ie - bad connection or paracitic short)

any electrical mods - amps, fogs?

 

(with the engine turned off)
1) between terminals with NO wires hooked up
2) between terminals with wires hooked 12v
3) between power bus side on fuse block and chassis -what is this exactly?
4) between terminals with the engine at idle (or lowest running speed) 14.8v

I'll check the other numbers soon as it stops snowing and I can clear the snow off the car (man i need a garage!) and post back in the morning ...

 

When your battery and brake light come on it means your charging/electrical system is running under 12 volts. My ex-gf had the same problem on her altima for 3-4 months before the alternator finally died on her. Get a multimeter and monitor the voltage during different conditions: start-up, low idle, etc. etc. and see what kind of voltages you are running.

 

Hey JB, if anything it looks like its overcharging. Almost 15v between the poles at the battery when running at idle and with those two idiot lights on. Only time I've noticed it lower is when the motor is off..

 

Is is a consistant voltage or is it erratic like jumping from 12volts to 15 to 13 etc.? What happens when you add load on to it like turning on your headlights, hitting the brakes, rolling up/down windows, etc? What's the voltage doing at higher revs?

 

Its fairly constant within about 0.5v in all situations. At higher revs the two lights arent on. They two idiot lights do come on briefly when I start to run the windows then stop and come back on when I get off the switch. Its weird.
Plus I just unhooked the positive cable again this morning with the motor running, lights on heat on high, just to make sure- she did not even skip a beat. Just kept on running until I got bored and put the positive back on a few minutes later..

 

Updated numbers. No Electrical mods save for a grounding kit

1) between terminals with NO wires hooked up 12.5v
2) between terminals with wires hooked 12.5v
3) between power bus side on fuse block and chassis
4) between terminals with the engine at idle (or lowest running speed) 14.8v

 

Same voltage that I have, goes up to 14.9-15.0 sometimes when driving, no dash lights on though.

 

Are you consistently at 14.8?

 

Just as a curiosity - check your grounding/grounding kit out. Had a similar problem - the idiot lights, drop in rpm - bad ground was the issue.

 

I've got so many aftermarket grounds lol, but which ground should I check?

 

with the motor running, yea..

 

this started before i put the grounding kit on. Actually I thought the kit my help with this issue but, no game..

 

How long have you been running like this, what's the highest it's peaked, any problems?

 

that's the weird thing, 3 months now. I thought with a bad alternator you'd have two weeks at best and as you can see, i've run most of the bad alternator tests and its passed- save for the high voltage.. 14.8 is the highest I've seen..

 

Are you measuring while driving, or while at idle? Do you have any in car electronics to measure voltage?

 

Not to come out of left field, but I have a similar problem. My car battery died two days ago after I left my lights one while I was at work. When I jump started the car (99 maxima SE), everything was fine except for the heater. The temperature could be adjusted and the modes changed, but the power setting went wild, it cycled through the settings: 0 (off), 1, 2, 3, 4, 0, 1, 2, 3, 4 at the rate of about 2 cycles per second. If I try to turn it off, it turns back on and does the same thing... it seems to think that that the "increase" button on the pannel is stuck. Any ideas on how to fix this?

 

this is all while parked- I tried a few different situations; lights off, lights on, lights on with heat on high. The idiot lights are off at higher rpms unless I do something like roll up the windows and even then its for a brief moment....

 

I bet you it peaks higher than 14.8 when driving. I'm going to have Tilley take a look at it this Saturday when I see him.

 

Had a similar issue with my old 626, the two idiot lights would come on quite consistently followed by funny wheeeeeeeeeeeee sound (which I believe was from a small relay). This lasted for a few months & I (like you) assumed it wasn't the alternator because everything else worked fine. Well, one day during a snow storm I was coming home from work out of town and it died...wasn't I pi$$ed!

 

Hows the car been so far?