intermittant battery light

Harleywood

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First off Hello to everyone. New member here and first time Pontiac owner. Hoping for a few answers and help. I'm pretty mechanical so big words don't bother me. :) I bought this car for my 17 yr old daughter. First car for her.
2002 Sunfire coupe, 113k miles. 2.2L I ran the vin decoder and it didn't mention ecotec with engine identifier. Manufactured at the Fugigawa or Fugisaka Japan Plant. Don't speak Japanese so it's one of those two cities or one that sounds similar. :) Car had new front struts, rear shocks, brakes. All installed within the past year before I bought it on May 21, 2014. Alternator was replaced a week before I bought it. Coolant is clean and clear no leaks. No oil leaks or consumption or smoking. Had current emissions test sticker in April 2014 and passed. Car runs and drives great. A/C is ice cold and all electronics work. No power windows, old school cranks. Sunroof was working at test drive but quit working as soon as I got it home but that's another issue for a later date since it's closed.

Problem is an intermittent battery light. Came on when she was out driving and ran battery down to 6 volts and died. Would jump and run until you pulled off the cables. Put new battery in, car ran but battery light stayed on for the 5 mile drive home. Sat for three hours before restarting and battery light was off. Took to auto zone anyway, OBD hooked up showed alternator code but figured that was old since it was just replaced and hadn't reset yet and the battery light was off at time of OBD test anyway. Battery light stayed off for a week and came on again last night two miles from home. Drove 7 more miles to destination with light on. Parked and sat for 4 hours. Went to start light came back on but went off as soon as I left the parking lot. Made the 9 mile trip back home no problems and light has stayed off today after about 15 more miles of driving.

Light was off when the following tests were run.......

Digital meter at battery with car not running 12.6 volts. Meter reading at battery with car running at idle 14.3 volts. Meter reading at battery at idle with all accessories on, a/c at max cool and fan speed high, radio on, lights on high beam and wipers on high, meter reading was 13.2 volts. It was dropping slowly over about two minutes down to 12.5v with everything running at idle. If I'd had the patience to stand in the hot sun any longer I figured it would have just kept dropping. Did not run continuity test since alternator charge was obviously reaching the battery. The wiring harness from alternator to battery had been repaired with butt splices and all looked in good shape. I pulled, yanked and jiggled the repaired wires with car running and battery light didn't come back on while doing so. Repaired wires must be ok with no short circuits? Pulled, yanked and jiggled wire harness connector to top of alternator as well as the red power wire at alternator with engine running and light stayed off. Serpentine belt is brand new with good tension pulley and tight with no slippage. Battery terminals are clean with no corrosion just a little greasy grim. Nothing to serious that would cause problems. I'm stumped. My only conclusion would be the alternator is not the right size for the vehicle since the voltage was steadily dropping with all accessories on over time. Although at the rate it was dropping it would have taken a hour or two to bring the voltage down to a critical state. Or it could be a re manufactured alternator the previous owner installed instead of a new one and the windings have bad spots. Any agreements with my findings or are there other tests I could run or other solutions from someone with more knowledge than me? I welcome any suggestions or ideas. The car drives and runs and handles great and I'm hoping it's nothing costly and an easy fix. Would like to get this issue solved so as not to worry when my daughter is on the road alone.
 
sounds like the alternator was a bad rebuild, replace it.
 
That's what I'm thinking also. Would like to get the meter on it when the light is on just to be 100% sure. I'm 6'4" and my big hands are going to make routing the belt back on that transverse mounted 2.2 a chore. The removal looks easy. Everything right there in front and on top. My main concern was the computer or ecm and not knowing if that had any control over the charging system. I'm an old school shade tree mechanic. First car was a 1965 Impala hardtop. 283 power pack with a 2 speed glide. So If it doesn't have points or a rotor I'm lost. Thanks for the reply!
 
the computer depends on the proper voltage coming out of the alternator, the computer itself does not control the alternator voltage or at least not yet.
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Thanks again for the response. I wish I would have a gotten the receipt for the alternator when she had it replaced. Pretty sure she used a garage since she told me it cost about $350 for the replacement. Maybe I could have had it replaced again for free or paid the difference for a new one instead of a rebuilt one. I'll spring the 200 bucks for a new one and replace it myself. Relieved to be informed the computer has nothing to do with it. That replacement I'm sure would have cost more than I paid for the car. Thanks again for you help!

Do you now anything about sunroofs? It worked fine when I test drove it. Opened and closed completely no problems. When I got home I tried to open it and it moved about and inch or two and stopped. Tried to close it and it closed but not quite all the way. It sticks up about a 1/4 inch above the roof line in the rear. It has rained since then. Not a little rain but a hard thunderstorm with sideways blowing rain and about 2-3 inches in a couple of hours. I sat in the car with sunshade open checking for leaks during the storm. Ran my finger all the way around the sunroof and all was dry. Bad charging system/alternator or weak voltage wouldn't affect the operation would it?

When I try to open the glass you can hear the motor running but the glass doesn't move. Motor runs constantly until I press the button again then stops. When I try to close it motor runs but only when I have the button depressed. Motor stops running when I release the button. I there a manual way to close it all the way without removing the headliner. I've noticed four torx head screws that appear to hold the glass to the track. If I remove these screws can I remove the glass to gain access to the track to check for an obstruction and to check the operation of the track with the glass removed? Really would like to get it working again but have been told by a few non mechanically inclined friends that sunroof repairs are costly, upwards of $1500 bucks and that's about what I paid for the car so that's not going to be an option. Just really concerned about getting it closed all the way. When you shut the drivers door with all the windows up the positive air pressure created in the cabin is relieved out of the sunroof glass where it's not completely closed in the rear. Over time I think this may cause a leak from the constant flexing of the track assembly each time the doors are closed. Suggestions, ideas? Or should I just change to full coverage insurance and a hammer? LOL
 
Thanks for the reply. Looks like I'll be dropping the headliner. :(
 
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