stupendousman

Hi,

For the past few months my battery light has been coming on intermittently, but never stays on consistently. Yesterday as I was driving in to work, the dash electronics started acting strange, the speedometer stopped working, several warning lights started turning on, and if I had the lights on and windshield wipers going, the engine would start to run a little rough. Got to work, turned the car off, tried to restart it, wouldn't start. Let it sit for a few hours, started up fine. Checked the battery voltage, it was fine. Drove it home last night, no battery lights, no strange dash behavior, engine was fine. Drove it in this morning, intermittent battery light again, but dash was fine.

I've had the battery charged at a parts store, they checked it out, said it was fine and that the alternator looked to be working fine too.

If I measure the battery voltage, it checks out at around 12-12.5V when the car is turned off. When the car is on, it jumps to around ~13V, and it will charge the battery up, so I'm assuming the alternator is working fine too.

Anyone else experienced anything like this? My co-worker and I think it sounds like spotty connection somewhere with the alternator...I'm guessing the wiring harness that connects to the alternator. I've re-seated the connector, but haven't tested it since.

Any other thoughts?

Thanks for any input!
Drew

lazlong

Sounds like a bad ground. Check and/or replace grounds as needed. Start with the one going from the block to the radiator support. There's one from battery negative going towards the fender and one under each fender (just remove the inner fender).

Hondaguy83

Looks like your alternator is showings sign of going out soon

stupendousman

Hey guys,

Thanks for the input. Sorry for the delay, I didn't realize anyone had responded

lazlong - I've checked the block to radiator ground and it seems solid. I'll try to check the ones under the fenders.

Hondaguy83 - I've had it tested at an auto parts store, and they said it looks just fine. Not that they couldn't be wrong....I just had it replace a little over a year and a half ago, so I'm hoping that it's not the alternator. Will an alternator begin to go out intermittently like that? The last time my alternator went bad it just went, no signs. I'm not familiar enough with alternators to know if they only go catastrophically or will go in small steps. Guy at the parts store said it sounded more like the alternator wasn't being communicated with properly.

Looking at the wiring diagram it looks like there are some wires that go to the under dash fuse box, I believe to the MCU, and there are some that go to the PCM...any idea where the PCM is, or where the MCU is? I'd like to just double check those connections too and make sure they're solid.

Thanks again!
Drew

MadMechanic

Im willing to bet money its your alt. If you can jump your battery to start and disconect the neg side of your battery. if it stays running that means that your alt is good and still charging the system.
If it dies instantly then your alt it bad.


good luck

stupendousman

Hey MadMechanic,

That's the strange thing...I don't have to get a jump to start. If/when my car dies, if I let it sit for a few hours, I can start it up again...usually with a little difficulty the first time, but then after that it will start up no problems. Seems to me that if the alternator was totally bad, I would need a jump, and would continue to need a jump until I fixed the alternator.

I've also read that disconnecting your negative battery terminal while running can be bad because it removes the battery load from the charging system and can ramp up the alternator output voltage, thus frying a lot of your electronics. I have no way of verifying if that's true or not, but at this point, I really don't want to take the risk of frying my whole electrical system

This problem I'm seeing seems to only begin after I've been driving for at least 15-20 minutes...which makes me wonder if it's heat related somehow? I dunno...just typing out loud.

alphalanos

yes dont disconnect your cable while the car is running thats an old school trick on old cars. new cars can get seriously messed up doing that. have u checked the belts to make sure they arent slipping or something when it heats up. I think I would take it to an actual shop to get a better test done.

stupendousman

Hey alphalanos,

Thanks for confirming that for me. I wasn't sure, but it sure sounded right. I'd rather err on the side of caution rather than fry my electrical system

I checked the belts while the engine was cold, but I didn't think to check while the engine was warm (and not running of course )

I'd rather not take it to a shop if I can get away with it...money's pretty tight right now, and the problem is so intermittent I don't know that they'd be able to do a whole lot for me.

Is there some sort of test that a garage can do that an auto parts store can't? They had some kind of testing apparatus that checked the battery and the alternator, both of which checked out.

Thanks!

EM2abe

how did they check your alternator? did they put it in a huge machine that makes it spin and all that good stuff?

i ask because i am pretty sure its your alternator going out. those are the exact symtoms that my car had when my alternator died. i just had it rebuilt for $70 and put it back in there.

jmvtec05

Had this same problem 1 1/2 months ago..Replaced alternator....problem fixed..em2abe is right on the money^

bairdandrew77

It really sounds like it's the alternator. Doesn't Autozone do free alternator tests?

stupendousman

bairdandrew77 - Yes, they do. I've had them test it as well as Advanced Auto Parts, both time battery and alternator check out.

EM2abe - They just checked it with a little handheld tester, couple of clips on the battery, one clamp on the battery cable.

Of course, now the really frustrating thing is that it's completely stopped having problems for the moment. We've had some cooler weather come in, so maybe that has something to do with it? I just wish it would go out catastrophically (without damaging anything else, of course!) so I would know for sure. It's a lot of trouble to go through only to find out it's not the problem. Everyone's right, it totally sounds like the alternator, but I would hate to do all that work and then have the problem crop back up again.

I did have a thought yesterday that I still need to try out, and it makes great sense...This summer my brother-in-law and I changed my compressor, which of course in my car, means you have to loosen and move the alternator. So maybe the tightener bolt is just a tad too loose and the belt slips on occasion. Seems plausible to me. I'll get under there this weekend and give it a go.

Thanks everyone for the input!
Drew

EM2abe

take your car in to autozone or oreilleys. they'll do a real test on it. but personally, i say dont waste your time and just get it rebuilt. that way you have a brand new alt. pretty much. and you wont have those specific problems. good luck.

MadMechanic

you will not fry your electronics on the newer cars. I do this for a living/everyday. Im 100% sure.

EternalHour

He has clearly said several times he had the alternator tested...Put a multi-meter in your car, if it starts acting up again pull over and immediately test the voltage on the battery. If it tests at <12v then your alternator should be fine, if not, it is probably bad. Could be the belt but I have doubts a minor slip would cause the battery to drain. Check the teeth on the belt, if it has been slipping significantly you should be able to tell.

alphalanos

Ive also had autozone test an alternator and say it was fine, then have a garage say it was bad. replaced alternator and problem was gone. Could it have been a bad connection? possibly, but im not totally convinced about autozone testing

eviee1973

You can purchase a digital voltage indictator which plugs into you cigarette lighter socket to give you an indication of voltage fluctuations, and system charging status. Bought one for less than $20.

REAL TIME

iTrader: (5)

Your alternator is bad reading at 13 volts when running. It must read above 14 volts. Replace alternator and don't get no refurb alt. you get what you pay for.