Ammeter pegs

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Jul 13, 2017 | 01:14 AM

tbm3fan

Thread Starter

Cargo Master

Joined: Jul 2006

Posts: 3,014

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From: Concord, CA

Ammeter pegs

Today the moment I started the truck the corner of my eye caught the ammeter pegging all the way over to the positive side and sit there awhile. Have never seen that before and generally know that if the ammeter did that continually I would be severely over charging the battery. Nonetheless, it has got to mean something.

First chance I get will be to check voltage at the battery with my multimeter with the engine off and then running. The wiring harness in the engine is fairly new, the voltage regulator is a made in USA Motorcraft electronic, the battery is one year old and always disconnected when the truck is sitting.

Jul 13, 2017 | 11:45 AM

Crop Duster

Logistics Pro

Joined: May 2015

Posts: 4,474

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From: Tri Cities, TN

Can't believe no one has taken a guess at this. So I'll go first. My first thought would be the battery is getting weak. I would try a different battery to see if it changes anything. Or the starter is pulling way more amperage than it should. I think as long as the charge rate drops off after a short time the voltage regulator is probably OK.

Jul 13, 2017 | 11:54 AM

daveengelson

Lead Driver

Joined: Aug 2003

Posts: 6,305

Likes: 18

From: Boulder Creek, Ca

Quote:

Originally Posted by tbm3fan

Not an authority: If the truck has set for any length of time, or working on the truck leaving the ignition on for extended period of time I find the alt will peg to the positive side but usually within a minute or so begin to move to the center. If the multimeter confirms current thru circuit is correct then I suggest check wire insulation and connections to insure circuit is not grounding out, especially at the gauges. I installed a fuse inline with the circuit, also purchased the block but never got around to installing since the fuse has done the job over the past 15 years. Anyhow, food for thought?

Jul 13, 2017 | 08:09 PM

66v8baby

Fleet Mechanic

Joined: Sep 2016

Posts: 1,459

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From: Southern Maryland

Quote:

Originally Posted by Crop Duster

Both of these are plausible causes. The ammeter is indicating a large inrush of current. The question is does it only peg out when the starter is engaged, or does it stay pegged for a little while after it has started? If it's only while the starter is engaged, the problem is either with the starter or the wiring to it. If it stays on longer, drive it around long enough to build the battery back up. It might just start working normally. Or you could take your battery in to a parts store that can check it's health.

Jul 13, 2017 | 11:11 PM

SuperSabre

Laughing Gas

Joined: Dec 2010

Posts: 1,091

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From: Tucson, Arizona

I had my amp meter peg on full charge a few years ago. Problem was the old non-electronic voltage regulator. Points inside it were sticking. Replaced voltage regulator with modern electronic version and problem was solved.

Jul 15, 2017 | 04:57 PM

tbm3fan

Thread Starter

Cargo Master

Joined: Jul 2006

Posts: 3,014

Likes: 91

From: Concord, CA

Ok, got to the engine last night. Immediately on starting the multimeter read 14.0 volts. Once into idle the mater read 14.1 volts the entire time at any rpm. If lights were turned on it dropped to 14.0 volts. The gauge came down to center but does react a lot slower than the multimeter. Think I'll stand pat with it for awhile.

Jul 17, 2017 | 07:36 PM

spurredon

FTE Legend

Joined: Jun 2004

Posts: 32,044

Likes: 2,430

From: Upstate NY

Are you having any other electrical issues such as battery drain like there may be a short somewhere or is everything else fine just the meter reads high? A burnt out voltage regulator can cause these problems. I just learn this on my truck a few weeks ago. After a lot of messing around, since last Fall before I put it away for winter I had been chasing trouble. Finally found a bad burnt trace on the voltage regulator.