hello all,

had a weird situation the other day. was driving home late and the battery pretty much died. left the car overnight and came back the next day to jump it. it would take a charge but would die shortly going down the road. after an overnight trickle, it would be at 13v then drain to about 9 when the car would just die out. one would figure that it was the alternator but read on...

fast forward to today. ive since replaced the battery with a fresh one and a new reman alternator. the car is consistant at 10.5-11 @ the dic and if i have the headlights on w/ the highbeams, the window switches depressed down, the radio and ac on, ill get the "low voltage" light on the dic and it will be around 9.8v. even when i turn it off with the car running at 9.8v, if i put the key in and turn the dic to voltage, it will report 11.0-11.3 volts. im getting a constant 10.8-11v across the terminals. the only places i have not checked are the connections at the starter. all of the battery terminals are torqued to 11ft/lb and the alternator bolts are tight as well.

nothing major installed in the last 8 mos. car has a 383 and a procharger. before anyone mentions, the belt is somewhat new and is intact and not slipping.

i checked the fuse box both under hood and footwell and the obvious fuses (bcm pcm etc) are not blown or any issues withstanding.

any ideas?

 

Have you looked at the battery cable to the solenoid connection? That's where the car gets its power from.

 

Sounds like the alternator is not charging to me......just a thought.

 

where is this solenoid?

 

Its attached to the starter. Remember that the battery connection there is electrically hot.

 

ok guys, heres an update....

battery is still dying.

when i hook up to the post with the ohm meter, im getting 12v at the battery.

when i ground the black side to the alternator casing and the red side to the pos side of the battery, im getting 12v.

when i hook the red side up to the plug on the back of the alternator and ground to the alternator casing, i get .2v(which is correct from what ive read).

whats the best way to see if the alternator(which was recently replaced with a reman) is good? obviously the battery is taking a charge from my trickle charger and not from the alternator. when i took the car to the parts store, the guy couldnt get a reading from the alternator(dont know why).

the circuit goes batt-> starter-> alternator right?

thanks again.

 

Sounds like you got the wrong alternator then.... take it back.

 

C5 Alternator info -

POST #5 http://forums.corvetteforum.com/c5-t...eck-first.html

POST #8 http://forums.corvetteforum.com/c5-g...lp-please.html

And more Info http://forums.corvetteforum.com/c5-t...e-experts.html

 

When you get this solved please share. I'm experiencing very similar situations. I've got new alternator, still have problems. One time it is reading 13.6 on DIC. Crank and run the car two hours later its as if the alternator is not functioning at all.

 

another update...

replaced the alternator, no luck. i had the guys at the parts store check it there so i know it was good, sure enough, its putting out 14v.

its as if the alternator doesnt get the signal to start charging. i believe this is signaled by the 3 wires on the voltage regulator, the only prong on the top of the alternator.

can anyone comment on where these wires go or where i could check the end of the circuits at? from what i can physically see, they go into the loom that the fuel injectors go into and back underneath the cowl.

fwiw, i did clean the 2 grounds in the engine bay per bills post.

edit: also, the dic is mirroring the physical voltage at the battery, so its not like the dic is off or something. whatever voltage is at the battery is also at the alternator, so i belive that circuit is not damaged.

 

Battery Cables: I had a similar problem. Battery would not start the car after sitting just a few hours even if it was on the batter tender. Noticed though that if jiggled the negative battery cable the car would start and the battery would charge properly. Replaced both cables and no problems since.

 

Someone found a fuse between the alternator and the battery cable at the starter, down close to the starter. You might want to look there.. I"ve never seen it but heard here in the forrm its there.

 

well,

i dont know that there is anything wrong from the battery to the alternator because the alternator is reading the same voltage as the battery, as in they are tied together. its the return path from the alternator. i know the alternator is on the same circuit but its the activation of the alternator.

 

Another tidbit is that the PCM controls the charging of the alternator. Pull your codes and see if anything is showing there.

 

I think I might be experiencing the same behavior. My car died on Saturday. I took the alternator and battery to be tested. Both tested fine and I had the battery charged. I reinstalled both, car ran but the voltage was around 11.2-11.7 on my DIC. I drove around for about 30 miles, when my voltage popped up to 13.2-13.3 and has stayed there. I wasn't able to find anything wrong with my cables, but you can't see much of them. Does anybody have a picture of what our harness looks like?

 

tech: i dont man, sorry


does anyone know how to diagnose or what pin assignments are on the voltage regulator (the one plug on the alternator) so i can test for voltage or the "signal" telling the alternator to start charging? mine has 3 wires and they are all different colors. im sure i can test voltage there to see if the pcm is communicating with the alternator. codes wont tell me anything other than its not seeing it.

thanks to all that have helped so far!

 

Send a PM to Bill Curlee. He's the electrical expert here.

 

well guys, heres the scenario...

after much time changing out all of the different components of the c5 charging sytem, i got frustrated and bit the dealer service bullet. at $100/hr X 2, it turns out that my battery cable going from the battery was melted by the passenger side header. the car has slp mid length headers and apparently the cable became loose and just melted, hendering the ability for the alternator to charge.

i dont know that i 100% trust this, but i did buy a new cable kit from gm and will pick up the car tomorrow and do the install. fun part is that the passenger side header has to come out to get to the wire.

this got me to thinking though, how was i able to see the battery voltage at the alternator lug? if the cable wasnt intact, the voltage should be lower going to the alternator, just the same as coming from the alternator? unless the voltage that i was seeing was from power coming off of a different circuit but at the alternator, if that makes sense..

either way, i dont know if this is going to work but they obviously theyve put their eyeballs on the cable that i didnt see.

ill respond with updates after i get it swapped out. thanks to all that have participated thus far.

 

another update.

it is confirmed. the battery cables at the starter are indeed fried. there are 2 wires there, one coming from the alternator and one coming from the battery. the ones coming from the alternator are toast, severed in two.

 

We did have the same problem! Was the total repair bill? Did they replace the battery cable?