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Old 04-11-2012, 11:26 AM
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A quick voltmeter question

I have a 96' silverado.
Recently I had a strange electrical problem that I havent figured out. Got in the truck to leave from work, turned the key and it was flat dead. No response from the key. No dash lights or anything. So I left the key on, and popped the hood, so someone could jump me. Went back to turn the key off and grab jumpers, and the dash lights and dome light were now on.

So I hit the key and everything went back dead again. I eventually monkeyed with it and got it running. It didnt want to run good for about 30sec then cleared up and I drove it home. Got it home and checked the bat voltage with truck off, and it was 13.00v. Checked the voltage at the junction terminal on drivers inner fender. It was 12.6v. I didnt have a replacement wire, so I added another battery cable from the top battery post over to that junction terminal. And now have 12.88v.

Anyways, my question is, what should my dash voltmeter read typically. Ever since ive owned this truck (10yrs) its RARELY ever read 14v. Usually below it. Either halfway past 12, or 3/4way past 12. And never above 14v.

Its only recently occured to me that this might be a problem, and might need a new alt. Im gonna check output of alt here afterwhile. Just curious in the meantime of what my voltmeter should typically read. I assum 14v nearly all the time.

Another thing last night, I popped the hood checked the tranny fluid. While checking the tranny fluid, the truck just died. It didnt struggle, just flat died. This hasnt ever happened before. I hit the key and it fired right back up. ?

Im pretty sure, when I die and go to hell, this truck will be there waiting for me.

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Old 04-11-2012, 11:50 AM
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When running it should be about 14V. You initial problem sounds like a bad battery connection. I have seen similar issues several time
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Old 04-11-2012, 02:04 PM
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X2
Bad connections -- very common.
Also, the battery could be going bad. Get it load tested at one of the auto parts stores.

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Old 04-11-2012, 04:42 PM
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X3 on the batt posts/connections
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Old 04-11-2012, 09:29 PM
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I checked the batt while running. Its 14v. The batt connections look good. No corrosion. But I will remove them and clean them.
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Old 04-12-2012, 01:29 PM
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Usually, a bad connection can look OK.
Cleaning and testing is the best way to find a bad connection.
Granted, intermittent bad connections are very tricky to find.
Sometimes a battery cable will be defective and no amount cleaning will help unless you replace the terminal ends. This is not easily done without special tools. So replacement is the best move.
A load test of a suspect bad connection can be done by using a voltmeter connected across the connection. Apply the load, cranking the starter for example, and observe the voltage dropped across the connection or cable in test. This will give a reading of the IR drop aka voltage drop across the connection. Generally, no more than .5 volt should be present but more important is a consistent (non erratic) voltage reading.

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Old 04-12-2012, 01:38 PM
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Make sure you check both ends. A bad connection at the block for the ground is not uncommon
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