Battery light

Tiny
JAY DERR
  • MEMBER
  • 2008 PONTIAC G5
  • 2.2L
  • 4 CYL
  • AUTOMATIC
  • 75,000 MILES
Recently we replaced the engine (2.2l ecotech), from another 2008 Pontiac G5 with the original engine that blew a had gasket. All went well with the changing of the engines. All components, (air conditioning, alternator, starter), were re-attached to the new engine in orderly fashion, and the harness reconnected. We double checked all connections and grounds. It fired up easily, and ran smoothly. While test driving, suddenly the battery light came on, and the car soon stopped running. We replaced the alternator with the one from the original engine and installed a new battery fully charged. Still the battery light came. The car ran perfectly until the battery drained. We had the alternator tested, and it was putting out 12.4 amps, not great, but the tech assured us that it should still function. We installed a new belt, a new cooling fan relay, changed the crank and cooling sensors. Still the battery light comes on soon after the car begins operating. Do you have any ideas on what the problem is? What we may have, or have not done to cause this to happen. What frustrates us most, is that the engine runs perfectly, so long as the battery has sufficient life.
Tuesday, December 5th, 2017 AT 1:04 PM

8 Replies

Tiny
CARADIODOC
  • MECHANIC
  • 34,330 POSTS
Are you sure that is 12.4 amps and not 12.4 volts? Either one is totally unacceptable. A good, fully-charged battery will read 12.6 volts. It can be expected to be drawn down to 12.4 volts or less when the charging system is not working and the battery has to supply all the current to run the car.

12.4 amps is not likely to be what the generator is developing. Under a brief full-load output current test, you are going to get very close to the unit's maximum current it was designed to develop, one third of that, or 0.0 amps. When one of the six internal diodes fails, you will only be able to get exactly one third of the maximum current. To get 12 amps would mean you have a 36 amp generator with a bad diode. That is not possible because the smallest AC generators today are good for around 90 amps. If you car has daytime head lights that you cannot turn off, 12.4 amps is not enough to run those, the fuel pump, and all the computers on the car. The battery will have to do that until it runs out. That will be in as little as a half hour.

There is a way to get less charging current but more than 0.0 amps. That is with a badly-slipping drive belt, but that would set up a horrendous belt squeal. If you have weak or intermittent power steering assist at the same time, a good suspect is the crankshaft pulley. On a lot of engines that pulley is a cast ring glued to the center hub. That bond often lets go, then the drive pulley slips, usually with no noise, then the belt-driven accessories run too slowly.
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Tuesday, December 5th, 2017 AT 1:49 PM
Tiny
JAY DERR
  • MEMBER
  • 4 POSTS
Thank you for your quick response, and yes I am sorry, 12.4 volts. I will check to see that the belt is, in fact working properly. What puzzles me, is the fact that the old engine, before the head-gasket leak, ran perfectly fine, where the electrical and electronic gear is concerned. So being that the problem, which was fixed, by installing the newer engine, had nothing to do with it. Why it suddenly fails with this newer, way less traveled engine? It is truly a mystery to me, because I am not all that familiar with the newer computer run vehicles.
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Tuesday, December 5th, 2017 AT 4:04 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Can we check to make sure the ground strap from the engine block to the frame is intact tight and clean connections? Also I would check the positive battery cable for internal corrosion.

Here is a wiring diagram and a guide to help us do some checking

https://www.2carpros.com/articles/how-to-check-wiring

Check out the alternator diagrams (Below)

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Thursday, December 7th, 2017 AT 7:22 PM
Tiny
JAY DERR
  • MEMBER
  • 4 POSTS
Thanks again. You guys are great. I did check the pulley, as suggested, and it seemed in good order.I will check that, and ty for the "wiring check thing. I will let you know the results.
Thanks again.
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Thursday, December 7th, 2017 AT 7:31 PM
Tiny
JAY DERR
  • MEMBER
  • 4 POSTS
I was sent a how to install the alternator in a 2008 g5 2.2.L eco-tech engine. I followed the clear video instructions, and installed it accordingly. The video shows only the two small wires, (orange and grey, with the plug in on the end), and the near by power lead going to the post. Here is a diagram of the manner in which the video instructed to install it.
However, there seems to be a short ground wire, that seems to also connect from that post, to the engine. I inquired to the mechanic who sent me the how-to vid, and he said that it should not be necessary, to ground that post out, because the alternator is bolted to the engine block, which should provide the ground. Under his advice, I removed it, and still seem to be facing the same no charge to the system problem. Was that additional ground from the power-lead post to the engine block actually a necessary factor?
Also, is there a fuse-link or something in that power-lead line somewhere, that may be the reason that the system isn't providing a charge from the alternator? This thing is driving us nuts, because everything worked perfectly fine, electrically, before that engine was replaced. Is it possible that we may have accidently switched the power lead to the alternator, with the one from the air conditioning unit, just below it?(I say we, but' he' is more true, and I am saying so, for him to read later.)Proximity, and the diagram of the harness seems to indicate that it is correct, but. Hey any straw is worth a grab, when you are grabbing at straws like we have been. Once again. Thanks for your time.
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Thursday, December 14th, 2017 AT 7:59 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 54,137 POSTS
Hello,

The alternator should not need a ground wire I think you hit it on the money with a main power fuse being blown here is a wiring and fuse panel diagram to help you test to confirm the failure and get it fixed.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the diagrams (Below)

Please let us know what you find. We are interested to see what it is.

Cheers, Ken
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Sunday, December 17th, 2017 AT 4:20 PM
Tiny
ROBERT ROSS2
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When you replaced the engine all of these connections were removed so you will want to check them. It happened to me 1,000 miles from home. here is a video I made about it:

https://youtu.be/hH4AUaNBt9I
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Tuesday, August 20th, 2019 AT 12:06 PM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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Thanks for the video look beautiful where you are BTW. Excellent addition to this thread! Please feel free to help out whenever you are on the site :)
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Tuesday, August 20th, 2019 AT 3:24 PM

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