I can't get my 2003 Saturn Ion alternator to charge the battery.

Car runs fine until the battery dies

When it is charged I've got ~12.2 V at the battery in the trunk

The battery is about 5 months old and tests good with a load tester.

I've got 12.2V at the under-hood post on the main fuse block

I've got 12.2V at the large red wire bolted to the battery

With the car on this voltage does not change. Never jumps up to 13.5~14V like it should

I've confirmed that the (possible) fuseable link wire from the Alternator to the starter is intact.

I pulled out the alternator and had it tested at the local parts nightmare. It tests good. I stood there and watched him do it after the first place i went to told me it was bad but then couldn't figure out how to actually connect it to the machine.

I've cleaned all the connections from the trunk, the starter, the alternator, the ECM, the pigtail for the field/regulator connection at the alternator.

As I understand it, when the key is on I should be getting 12v to the small red field wire on the regulator.

I do not have this voltage. I don't have *any* voltage at either of the 2 wires going into the side of the alternator.

I've confirmed that the small red wire has continuity through the harness up to the ECM. Once it goes into there and dissappears under the dash who knows.

The battery light is on when I turn on the key, goes out when I crank it and comes back on once it starts.

Just for testing purposes could I connect the field wire (the little red one in the side of the alternator) to a known good 12V and see if the alternator starts actually putting out 14v?

 

Have you checked to make sure theres no breaks or frays in the wire?

Is the post on the fuse box tightened enough?

I'm sure you could connect it to an outside source.
Check the battery cable from the box to the battery?

 

I see this was never followed up on but I am having the same issues with a 2004 Ion 3. The differences are, when referring to the 2 small red and grey wires that plug into the alternator and go to the ECM, is that with with key on I have 5 Volts the red wire and "0" volts at the grey wire. I understand that the EMC turns on the Alternator and turns it off if it senses a problem. When the car starts up battery light goes out for about 10 seconds and then comes back on. When it is running with Battery light on there now is only 1.8 volts on red wire and 1.7 on the grey wire. I have cleaned all grounds a and battery posts/connections. The alternator was removed and tested good. The continuity on all wires involved are good. I am starting to think this could be an ECM issue? Either it is bad or has a bad ground? It is grounded internally but the wiring has to be connect some where to ground as the ECM case is not grounded . What also occurred is after I put the alternator back on after testing it charged 14.4 volts for about 10 minutes in shop then quit charging so I then took it out for a drive a 2 mile loop. After driving about a half mile it started charging again this lasted about a mile and then it quit charging and then reverted back to just showing a charge for the 10 seconds after starting as it did before. Any help with this would really be appreciated.

 

I have a fsm for the L series and they use the same engine as your Ion. I will take some pictures of the diagnostic trees and see if that will help.

 

 

Hey thanks for the pictures ...these will help immensely! I am working on my grand daughters Ion and I am finding out that finding diagrams nowadays on these cars is challenging .

 

So it turned out to be the alternator.

I tried a new ECM and that made no change. I had two different replacement reman. alternators from OReilly tested out of the box and they tested good. Even went to an old school alternator shop and they threw it on their real test bench and it was cranking out 14.5 volts.

I went to an actual auto electric shop and had them take a look. They hooked it up to their terminal thing and could see the computer was sending the 5v to the small red wire but the regulator was not turning on. I had them pick up a new OEM-ish alternator from their supplier and that worked fine. The tech told me that they have seen this many times where the cheap remanufactured alternators just don't play well with the ECM.

Doesn't make any sense to me if it works on a bench but I don't care at this point. Lol. I'm just glad it's working again just in time for my daughter to commute to her new semester.

 

Oh and thanks to everyone for your help! The documents really helped as I was tracing all this crap down and confirmed the way I suspected it was SUPPOSED to work.

 

Jsneddon
Yes that ended up being the problem....I put a third alternator on it and it started working as it should...if the ECM receives signal that there is a problem with the alternator it grounds out the 5 volts needed to turn the alternator on.

 

Thanks for letting us know the final solution. 👍