Battery light came on after replacing the alternator

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wintersilke
Posts: 32
Joined: Tue May 24, 2005 5:05 am

Battery light came on after replacing the alternator

Post by wintersilke »

2005 Vibe with 194k miles

Had to get a jump start today and drove to the part shop to test what they could. Battery tested fine but the 5 month old alternator didn't pass. Guy said that the error msg. said the voltage regulator wasn't working. I got a new alternator as it was under warranty and installed it.

Several hours later, the battery light comes on. I drive back to the part store and the alternator and battery test fine. I try to start the car to test the starter and it won't start. A jump from the store and it starts right up.

The positive terminal was nearly beoken off so I knew the contact was poor. I replaced the terminal, get a jump, and drive home. At home I replace the terminal. Car starts but idles really low; around 500 rpm. Voltage across the terminals is only showing 12.7V at that idle speed. Daytime running lights now won't turn on either.

I'll check the fuses when its daylight. I put the battery on a trickle charger so I hopefully have enough juice in the morning to take the kids to school.

Any ideas what I should pursue next if there is a problem?
jolt
Posts: 945
Joined: Sun Mar 02, 2014 2:07 am
Location: Twin Cities, Minnesota

Re: Battery light came on after replacing the alternator

Post by jolt »

Put an amp meter on it and check the amperage output as shown below. You can have voltage but if you don't have amps, you have no power.

INSPECT CHARGING CIRCUIT WITH LOAD
(a)With the engine running at 2,000 rpm, turn on the high beam headlights and place the heater blower switch at ”HI”.
(b)Check the reading on the ammeter. Standard amperage: 30 A or more


Also make sure all your connections are good. Don't be afraid to bend the terminals around at the end of the cables. If the terminal fails off, you had a bad connection and replace that cable.

Have the battery load tested https://www.youtube.com/watch?v=PjDcagchyl0
and check each battery cell with a hydrometer. https://www.youtube.com/watch?v=SRcOqfL6GqQ
Derf
Posts: 529
Joined: Mon Feb 04, 2013 5:19 pm
Location: NW Ohio
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Re: Battery light came on after replacing the alternator

Post by Derf »

Might be a ground terminal on the engine block/frame. Although you corrected the issue with the positive battery terminal, at the battery. The negative strap could have an issue. I believe the alternator and battery have different ground points, an interruption or bad terminal mount could prevent charging the battery, which might also explain the failed alternator.
2005 #10,524 Neptune Vibe "Bandit" Auto, Moon & Tunes 235k :D
1991 Pontiac Bonneville 3.8L "Granny's Whip" 142k (33nd Anniversary :o )
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calivibes55
Posts: 11
Joined: Sat Aug 29, 2015 9:13 pm

Re: Battery light came on after replacing the alternator

Post by calivibes55 »

The low idle is most likely being caused by your ECM "relearning" your car's idle curve, which happens when the battery is disconnected. This is normal - 20 minutes of acceleration/deceleration driving around town will fix it and it should return to normal. If it feels like the car might stall out run the air conditioner until the process completes, the extra load on the engine will prevent it from stalling out.
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