Specializing in the 3g CSM
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PostPosted: Thu Oct 18, 2018 3:45 pm 

Joined: Thu Jul 07, 2016 5:44 am
Posts: 42
Hello again,

So my car has been sitting in my driveway for about a month due to a major boost/vacuum leak and me not having the time to dive into solving the issue. So today I went out to start it up and got no power whatsoever. I immediately connected my battery charger (cheap one) and began charging it. After about an hour I went to check on it and it had tripped an “open cell” code, however I bought this battery in April do I reset the charger and it immediately threw the full charge code. Checked the battery voltage and it said 12v or something very close to that (it fluctuated between 11.8-12.4v). However when I switch the headlights on nothing happens and when I turn the iginition nothing happens. What should I check first? I am going to pull the battery after work tomorrow and bring it to the store so they can test it there with their equipment. However, if the battery is fine I don’t really know where to look. Do these beautiful cars have a lot of electrical issues as they age? If so, can someone point me in the correct direction so I can get the thing running again and begin solving my boost/vacuum leak problem? Please I need help with this!

PostPosted: Fri Oct 19, 2018 9:52 am 
CSM Junkie
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Joined: Sat Sep 22, 2012 6:40 pm
Posts: 667
Location: Indianapolis, IN
It is an old car with, most likely, the original grounds. Check all the grounds and replace those that don't show full resistance.

1991 GVR4 1025/2000 (PTE 1200's, 16g, DSMLink v3, gm-maf, eagle/ross, .020 over, 272's, EVO VIII Wheels)
1992 GVR4 866/1000 (getting everything from above)

PostPosted: Fri Oct 19, 2018 6:16 pm 
The Silent Administrator
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Joined: Wed Dec 24, 2003 3:32 pm
Posts: 9413
Location: Ottawa, ON, Canada
Battery is 12.6 volts minimum standing voltage. If you have less than that and it is a true indicator of the state of charge of battery, then you are on the slippery side of the slope.

Taken from the battery university web page, this heads the nail on the head:

state-of-charge Average
specific gravity Open circuit voltage
100%1.265 2.10 6.32 8.43 12.65
75% 1.225 2.08 6.22 8.30 12.45
50% 1.190 2.04 6.12 8.16 12.24
25% 1.155 2.01 6.03 8.04 12.06
0% 1.120 1.98 5.95 7.72 11.89"

These are measured after 24 hours of rest, to let the battery normalize, but this can be an indicator of internal battery issues. You short one plate with another plate and you lose, 2.1V+ at 2 cells, being 4.2V of the 12.65V, leaving you off the chart and unable to start. Take the battery in to be tested on a capacitance tester - all the major chains should do this for free I suspect.

Other than the battery, you would be likely in the area of battery terminal cleanliness and as Thom said, checking your grounds. The battery cables should be checked for resistance too, as it would only get worse with a load on it.

If you connect a DVOM in series with your positive wire and the battery and hook the battery back into the equation (but do not have the key place at all!), see what kind of amp draw you get. Be sure to have a 10A model and keep a spare fuse around just in case you pop it! Be on the 10A setting not 1A and see what you get. If the draw is so small it doesn't accurately show on the 10A scale, then move to the 1A to get multiple decimal places for output.
We call this parasitic draw and anything from a failed diode in the alternator rectifier bridge, to a dome (those pesky door switches and sagging door hinges! or trunk or glove box light still on, to a module or ECU could be pulling in excess of what would be acceptable draw for most cars.
I vote 20-35 mA tops, anything more and you are looking at trouble or you own a corvette or a german vehicle that normally has a rather large battery anyways with a great RC rating.

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