Voltage Issues

1995 Monte Z34, 3.4DOHC
My car has developed voltage issues. Some sytems are running on less than battery voltage while others are running at 13.6 volts as expected. I
haven't done any diagnosis yet other than figuring out that my alternator is putting out proper voltage and that only some sytems are effected. I checked the voltages at the I/P fuse block, some systems running at 13.6VDC while others are running at 12.2VDC (at time of testing, sometimes this voltage drops to less than 10VDC).
When engine is cold, everything operates normally. After a 5 - 10 minutes of running the voltage drops.
Just looking for opinions on where to start. Maybe someone experienced a similar problem. Maybe listing what systems are effected and checking to see if they have a common ground or voltage source that is causing an issue?
Steve
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Steve any symptoms here with any accessories or electrical issues? I don't think grounds are a problem unless the ground in question was the one you were using with your voltmeter. Some volktage drop in small wired circuits is normal, but 2 volts is high, I have never investigated, routinely, circuits in the dash or fuse panel like you seem to be doing, I would like to try it on my 98 Lumina. See if you can isolate the circuits that drop to 10v and see if there is a common voltage source. Also how about harness connectors after the engine was reinstalled, particularly from the main harness to the fire wall or fuse block, not pcm, this I believe is seperate.

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Here are the circuits that are running at the lower voltage (from the I/P fuse block only):
12 - 5A Anit Theft 15 - 15A HVAC #1 21 - 15A Air Bag #1 24 - 15A HVAC #2 29 - 25A Wiper 30 - 10A Turn Signal 33 - 20A Power Locks 38 - 10A Radio 39 - 10A I/P Electronics, Ingition Feed
At time of testing, the "high" voltage was 14VDC and the "low" voltage was about 10.5VDC. The circuits listed above were all at 10.5VDC and the rest were at 14VDC.
Now to see what they have in common.
Steve

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They all lead me to the left side under hood electrical panel. What I found when I got there was a rather large voltage drop between the remote battery stud and the fuses. I disassembled the stud, cleaned it all up with LPS contact cleaner, put it back together and coated the whole thing with dielectric grease. All seems to be back to normal.
Steve

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"Steve Mackie" wrote:

I would check all of your grounds for starters. Every one you can find in effect areas.
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I would check the battery in your meter or try another one. Also what are you using for a ground? Same one for all checks? Check and reseat the connectors and check all grounds.

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Also your battery may be bad allowing a lot of electrical noise in the system which will give erratic dc readings....

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