Voltmeter or Charging?
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Junior User
Joined: Jul 2004
Posts: 86
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From: NE Kansas
Voltmeter or Charging?
My voltmeter drops very low on a cold start, then slowly builds to just under halfway and finally makes one quick jump to the where it should be. The whole thing lasts less than 30 seconds. Not long enough to get a multi-meter on anything.
Post Fiend
Joined: Mar 2007
Posts: 9,010
Likes: 5
From: Johnson City, TN.
That is because the glow plugs are still heating even after the light goes off. When you see it jump to where it should be is when the GP's shut off. Usually the lights get brighter at this point also.
Postmaster
Joined: Feb 2004
Posts: 3,266
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From: Levittown
With new batts you should not drop below 11.8/12v at startup.
I would test voltage before/during/after the cold start.
You will be able to see if the alt is weak. A 100% working
alt cannot push 14v with the gp's on. Its a huge load.
Bill
I would test voltage before/during/after the cold start.
You will be able to see if the alt is weak. A 100% working
alt cannot push 14v with the gp's on. Its a huge load.
Bill
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Junior User
Joined: Jul 2004
Posts: 86
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From: NE Kansas
Thanks for the specs Madvan. I'll run some diagnostics tomorrow. I had to make some leads for my multi-meter that would reach the cab first.
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From: The boonies by Dallas OR
Make sure both batteries are working. When I bought my truck it had 6 month old batteries, but it was hard to start cold plus the voltage really sagged when the plugs were on.
Almost a year later I was working on the electrical system and I noticed that the hood light didn't come back on when I hooked back up the negative lead on the drivers side. I found that the positive was very high resistance, so only one battery was doing all the work. I cleaned up the lead, and it starts MUCH better with MUCH less light dimming.
Almost a year later I was working on the electrical system and I noticed that the hood light didn't come back on when I hooked back up the negative lead on the drivers side. I found that the positive was very high resistance, so only one battery was doing all the work. I cleaned up the lead, and it starts MUCH better with MUCH less light dimming.