Are these voltage readings normal?

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Jul 12, 2008 | 10:03 AM

#21

knkali

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From: Northern Calif

our cars are telling us something. There is a problem and it is not your battery. We are not charging at idle. There should be 5v from the pcm to the alt at idle at the L terminal. in my case i have 5 at the pcm but when we plug into the alt the voltage drops to 1.3 so the L terminal is not switching on the alt as it should. If you are stuck in traffic on a hot day, you could run the battery down enough to cause the car to go into limp mode. I think the thing is when we drive the car we get enough juice back into the battery to get by. If i let my car set for say 5 minutes with the ac on and the cooling fans kick in the volts will drop to 11.7 ish.

If the rev extreme alt somehow can bypass this with the higher output then I am all over it but I think the problem is in the switching by the L terminal not the alt output.

Last edited by knkali; Jul 12, 2008 at 10:27 AM.

Jul 12, 2008 | 10:53 AM

#22

Joe_G

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From: St. Louis, MO

St. Jude Donor '08

Quote:

Originally Posted by knkali

Hmm.. I don't really have this problem, my car run enough voltage all the time, except first thing after you start it if you don't rev it a little to get the charging system working it'll stay low. The instant you give it gas the volts go up to 14 or 13.8 and stay there. With a full electrical load at my 750 idle mine will get to 12.5 but soon as I take off it's ok.

My car will do the chime at odd times though when I'm cruising, every time I look it'll have normal volts and the service charging system message goes away quickly. I have to say this problem started when I had a underdrive pulley on a year ago but don't know if that is coincidence or not. It's this odd cruising dinging I'd like to get rid of. I'll try flashing it and see what it does.

Thanks much for the tip!

Jul 12, 2008 | 11:07 AM

#23

knkali

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From: Northern Calif

ok you have been advised. I sincerely hope yours is OK. Mine went to 12.5 to then it will go to 12 then 11.9 but it takes some idle time. The average stop light I am fine too--we will see... If you havent done this start it blip the throttle to get your volts charging then let it idle with the ac on lights too and come back in 15 minutes. If you still have 12.5 then you are good to go. Although 12.5 with your idle and a ud pulley sounds very reasonable.

Last edited by knkali; Jul 12, 2008 at 01:28 PM.

Jul 12, 2008 | 07:29 PM

#24

knkali

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From: Northern Calif

ordered.
Thanks
will keep everyone posted

Jul 13, 2008 | 02:19 PM

#25

knkali

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From: Northern Calif

Tracy,
I forgot to mention that when they loaded the new PCM the "open L terminal circuit" message was displayed on there Tech 2 display. I wonder if a bad alt would cause this?

yeah, my wheels are turning all weekend about this.

Jul 17, 2008 | 09:51 AM

#26

knkali

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From: Northern Calif

goes in this morning

Jul 23, 2008 | 10:38 PM

#27

Joe_G

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From: St. Louis, MO

St. Jude Donor '08

Hmmm...this information is new to me...I wonder if this has something to do with the service charging system messages we are getting? Maybe our cars can't do some of the load shed or idle adjustments and thus are throwing the code?

http://forums.corvetteforum.com/show...71&postcount=2