jsc1648

This message appeared on the DIC when I started my 06 MN6 yesterday. I watched the voltage on the DIC and it would go from 13.3 to 13.7 volts. I could swear this is lower than usual. When I would lug it from a start it would drop down to the mid 12s though. Any ideas? Sound like an alternator issue. BTW, I have had a dead battery after 3 days of sitting. I usually keep it on a tender.

Thanks...

jnx911

Unfortunately you will need to see the dealer.

jsc1648

Took it in today and they diagnosed the problem as a horn issue. "The horns blew a fuse that are somehow connected to the alternator." Sounds pretty fishy to me. They replaced both horns and the fuse and are ready to send me on my way. Why should I believe this? I do know now why it wasn't honking while locking the doors. I never even thought to make sure the horn was working. Sounds kinda dangerous.

The only exposure to water this thing has ever had is from washing it. I feel like I'm destined for another trip to the dealer. But it's possible the horn was defective, blew a fuse and that trips the service charging system light.

1955 BelAir

I am getting the same 'service charging system' warning. Does not happen until the car has been running for 15-20 min, and up to running temp.

I will take it to the dealer next week and see what they tell me.

jsc1648

Does your horn work? I really don't use my horn, so I hadn't noticed it wasn't working.

Jeff

TXSTICK

Had that same problem in when I had my 02 and brought it to the dealer. They said everything was fine. Two days later the car was dead, no power at all. Turns out the battery shorted inside. when you put down your windows with the headlights on, do the lights dim? That is what I saw first. I would have the battery load checked.

jsc1648

Just to be safe, I think I'm going to buy an optima. Any recommendations as to which one to get and from where. Thanks,

Jeff

Aaron Pfadt

Hey all, I just confirmed the (or one possible) diagnosis of the 'Service Charging System' message. On my car, the horn did not work and a little digging around determined that it was the Horn fuse in the fuse box in the engine compartment. It is a 15 AMP fuse that is for Alternator Sensing/Horn. It is mini-fuse 2 for those that are interested.

So, check that before heading to the dealer. It might save some grief

-Aaron

jsc1648

I wonder if we had defective fuses or horns or what.... They replaced my horns as well as the fuse. Mine is an 06 with a VIN in the 20,000 range. You?
Jeff

KillerVette

i checked the fuse and it seems ok? should i change it anyway?

SomeoneTakeTheWheel

Check for loose nuts on the starter. That's what happened to me. The mechanic said "We used to see this all the time on the C5's, thought they'd have it fixed by now."

Yeah, me too.

Bill Curlee

I’ve done a LOT of C5 charging and battery drain investigating and troubleshooting and just started to branch out to C6. There not that much different. Here’s some info. Your C6 should be able to sit idle for over a MONTH without having any battery or starting issues. When the car is OFF, the BCM and module memory circuits go into a SLEEP MODE and the current draw off the battery is only 20-25 milliamps. It’s a Very small output.

Something is causing you C6 to either:

1. Something is not allowing the BCM/PCM to enter the sleep mode and reduce the current draw on the battery.

2. Something is either being left on when it should be off OR not shutting down when the engine is OFF.

3. Your battery is defective and not able to support the small long time current draw. Fully charging the battery and taking it to AutoZone, NAPA or Advance and having them fully test it will prove or eliminate that as the issue.

Some of the things to check:

Aftermarket accessories are very common to stay on and draw excessive current.

The interior lights can be set to stay on which will kill the battery in short order.

To measure the current draw, attach a DC AMP meter (able to read 10 AMPS DC) in series between the negative battery terminal and the negative cable.

When you first connect it the current draw will be high (approx 5-6 amps and it will/should drop off to the sleep current value within 5-10 min.

(If you do something to bring it out of sleep mode, (open the door bring the FOB near the car etc) it will take another 5-6 min to reenter the sleep mode.

See what you current draw is.

Normal charging voltage is 14.1 - 14.6. Depending on battery temp and charge status, it can be higher or lower 13.5 isn’t out of spec and I’ve seen it a few times on normally functioning cars.

You can see charging system fault during first crank but it should go out in short order. If it stays ON then theres a charging issue.

The BATT Terminal on the back of the alternator is the OUTPUT of the alternator. That wire goes to the main terminal on the starter solenoid and from there goes up to the battery positive terminal. If the connection at the solenoid is loose/corroded/damaged, you will have charging system issues. I have in the past, ran a test jumper wire from the POS Terminal on the BATTERY terminal to the BATT on the back of the alternator. If that improves charging voltage, the connection at the starter or wiring between is at fault.




BC

mack morrow jr

Keep in mind that the horn is a high energy pulling item.The cig lighter, horn and headlights are among the heaviest pull on batteries. I have a red top Optima and have had no issues. I may would go yellow if I did a lot of accessory running while the engine is off like playing the stereo while waxing or cleaning the car with the engine off.Yellow top is a bit more expensive and known primarily for reserve power . I never use any accessories when the engine is off so did not feel the yellow would bebefit me.

RDKING

Bill thanks for coming over to the C6 Section.

Tom's '07 Monty

I had the same problem. Horns went wild while parked in garage and no one home. Horns eventually stopped. A few hours later I came home. Car started and ran ok but service charging system light came on. Went to the dealer...horns had shorted out. Replaced horns, light gone no more problem. Service manager said they have had this problem on a few other C6s.

dgrant3830

The PCM monitors the frequency of the alternator therefore allowing the firmware to command the alternator to output more or less juice as needed. This monitoring is done at the Horn/Sense fuse. If that fuse is blown for any reason, the system won't work and you will get the Service Charging System message. ALSO, if there is any noise induced at that point, it will cause problems as well. A good example is changing spark plugs...some plugs will generate more noise and result in this monitoring point picking it up and messing with the alternator charging output.

fairystacie

THANKS so much! I saw this post and it was exactly what you said!

The Clevite Kid

If you are resurrecting such an old thread, we might as well include this one on the same subject:

http://forums.corvetteforum.com/c6-t...ng-system.html

My contributions are in posts 44, 52, 55, and 58.

Rikk427

I've had this happen to my 05 a couple times. Both times I loosened the wires on the starter solenoid, wiggled them back and fourth a bunch to try and rub off any corrosion then re tightened and its started charging correctly right after. I should probably take the starter off and replace the solenoid or replace the entire starter but at least I know what the problem is and I wont have to take it to the stealership.

Ratchet Thunderbolt

Nice post!