thevpops

Hello,


The Service Charging System has come up and gone a couple of times in last week (2011 C6 GS). I have in the meantime replace the battery and the alternator. It still gives me the message. Pretty disappointing. I'm thinking there is something in the fuse block. Any ideas or knowledge about this type of issue.


Thanks,


Jon

CadVette

Take a look at the cable and connections next. Make sure all the connectors are clean. I like to clean the connections with sand paper then put a dab of grease on them to prevent further corrosion. This process will make sure they are tight, clean and secure. Inspect the cables to make sure they are not rubbing on any surfaces or the insulation on them has not worn through somewhere. You can test your replacement alternator by putting a voltmeter across the battery terminals while it's running and verify that you are seeing over 14 volts. Beyond that you can test for battery drain with an ammeter on the negetive side of the battery cable and pull one fuse at a time until you can isolate the offending circuit.

brians98ss

Are you still seeing around 14V with the message on?

Are you running stock AC Delco spark plugs? It has been proven that aftermarket plugs can cause what you are seeing. Something about electronic interference. I occasionally have this message pop up and I am running NGK TR6 plugs.

thevpops

Can you please confirm that I could just as well measure the voltage from the alternator output. I expect I should read 14 volts if I measure the voltage potential between alternator and ground.

thevpops

I see 12 Volts (battery potential).


I have not changed the sparkplugs and have over 20,000 miles with my current ones, without problems. I can still try to check what type I have.

thevpops

As I asked CadVette, should I expect to read 14 volts at the alternator outlet peg?


It reads about 2 volts right now, when I run the engine (LS3 6.2L).

extrapilot

Running voltage should be at least 14, usually 14.7 at the alt. large lug.
At the battery while running, should read about .5 to .6 volts less, because of voltage loss thru the wiring.

CadVette

I compare the voltages at the battery. At rest you should have over 12.5 volts minium. When the car is running you should see the voltage jump to over 14 volts which would indicate the alternator is working correctly. If your getting 2 volts when it's running it sounds like the alternator. Going further, disconnect the battery and verify that it holds voltage without dropping. You may want to have a new GM alternator installed in it's place. Rockauto.com is a good source. Or have your original one rebuilt. You can buy a kit or find a shop around town that rebuilds them. Don't buy an alternator from your local parts store. They typicially only last one year due to cheap Chinese internal parts. Good luck.

thevpops

I had put in an O'Reilley $150 alternator last week. But I still did not get 14+ volts on the read out inside the car (on the DIC?). Only got the basic 12 Volts (or 11.5). I did not have my voltmeter then. Still, I promptly decided to take it back out, and returned it (on the basis that the pulley looked a way different). Still, it was puzzling -- did I then also get a bum alternator from O'Reilley?


Anyway, I just ordered the alternator from Chevrolet dealer, and will install it Wednesday. I have other problems with car I think (starting only when I jump it, even though I have new battery from last week), but I will make new observations on Wedsnesday once I install alternator. I doubt new alternator will resolve the no starting of course. Keeping battery on a low 2 amp charge for now, in case something is draining it. Thanks for help up to now.

thevpops

Just FYI -- I saw your suggestion about RockAuto.com.


I promptly now cancelled my alternator order with Chevrolet dealer ($670), and ordered it with RockAuto for $378 (includes the 2-day shipping service).


Thanks. That's a big saving, especially since I still expect to have to pay some amount to fully address all issues.

extrapilot

You are much better off getting a new one for sure.
Once you get the battery up to full charge, have that "Load Tested" to make absolutely sure it's good.
Most any parts store can handle this request usually free of charge.

tennblkc6

maybe I missed it but are you getting 14+ volts measured at the alternator lug while the engine is running?

thevpops

Measured only 2.16 volts when engine running.


I have a new GM alternator coming in tomorrow or Thursday. I may have further questions.


Thanks.

Z06FoEva

It sounds to me like you might have a wiring issue. With the car off measure the voltage at the post on the alternator and it should read battery voltage. If it does not read battery voltage then you have an issue between the alternator and junction box or battery. There is a fuse link on the alternator cable that may have gone bad. It's at the end of the alternator power cable that goes to the junction box. Hope that helps.

thevpops

Understood. I'll test that, and take a look at that too. I need all the trouble shooting tips. So, thanks.

Z06FoEva

If you test the post and it reads battery voltage with the engine off, then proceed to testing using the attached docs. It's a pretty simple system. Don't waste your time chasing your tail checking spark plugs and other nonsense. Troubleshoot the system properly and divide and conquer. Also, if you find that you are not getting the correct readings at the connector to the regulator you will need to check the output coming out of the PCM (located behind fender liner on passenger side wheel well). You will need to back probe the wires with the connector connected to PCM to take these measurements. I have attached the connector pin out view for your reference and the pins that you will need to test are highlighted. If the PCM output is good, then you most likely have a wiring issue between the PCM and regulator harness. You can confirm this by taking a resistance (OHM) reading of the circuit or do a voltage drop test across the circuit (should be less than 50mV). Good luck and stay patient. Electrical can be very frustrating but very gratifying when you get it figured out! Let me know if you need any more help.

cclive

I'm not at all convinced that it is the alternator, from the numbers you have given us. It sounds more like wiring.

thevpops

Right. I do expect some challenges after replacing alternator. I will probably have to follow the steps and documentation from Z06FoEva (message above).

thevpops

My battery is 100% OK. New alternator too.
When I separate the alternator cable from the alternator, and I measure at the eyelet, I get 12 volts approx. (engine not running).


When the engine is running, I get 5 to 6 volts at the alternator post, with the cable connected to the alternator.


When the engine is running, and I disconnect the cable, I get just under 2 volts at the post, again. Even though it's a new alternator (GM part).


Does some of what I'm saying exclude your fuse link theory? Any other thoughts.

thevpops

Hello, would you please see my note to Z06FoEva. Thanks. Kind of struggling here.