Idle variation, unknown cause
Thread Starter
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Lead Driver
Joined: Mar 2004
Posts: 5,372
Likes: 108
From: Northern Indiana
I just wish I could find it. I don't have any clue. The check valves in the HPOP is the only thing I could think of. But it makes a whole lot of no sense to me.
Elder User
Joined: Sep 2011
Posts: 979
Likes: 4
From: Vancouver
You need to check the alternator for ac voltage output. The "full wave bridge rectifier" inside the alternator cannot handle the kind of current that melted that screwdriver. I would bet some of the 6 diodes are no longer acting like diodes, i.e. they are allowing alternating current to flow into a direct current system that is not designed for it. Find a multimeter and use the A.C. scale to check from a positive terminal to ground. Report back! You may have damaged the wire windings inside the alternator or blown out the voltage regulator which cannot handle the surges of voltage change.
Elder User
Joined: Sep 2011
Posts: 979
Likes: 4
From: Vancouver
Also, if that were my truck, I would not drive it until that alt. is checked out or replaced. You can fry all the important electronics with an alt. putting out unregulated voltage, or AC voltage.
Thread Starter
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Lead Driver
Joined: Mar 2004
Posts: 5,372
Likes: 108
From: Northern Indiana
You need to check the alternator for ac voltage output. The "full wave bridge rectifier" inside the alternator cannot handle the kind of current that melted that screwdriver. I would bet some of the 6 diodes are no longer acting like diodes, i.e. they are allowing alternating current to flow into a direct current system that is not designed for it. Find a multimeter and use the A.C. scale to check from a positive terminal to ground. Report back! You may have damaged the wire windings inside the alternator or blown out the voltage regulator which cannot handle the surges of voltage change.
I did test from the negative battery cable to the cable coming of the alternator in the d/c setting and was getting 14.6V.
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Lead Driver
Joined: Mar 2004
Posts: 5,372
Likes: 108
From: Northern Indiana
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Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
Looks like you found a problem 
As your rpms increase, so does the AC/interference, which can cause all kinds of things to act strangely.
I'd replace the alternator. The findings coincide with the mode of injury, so that increases the likelihood that this is the "main" problem
As your rpms increase, so does the AC/interference, which can cause all kinds of things to act strangely.
I'd replace the alternator. The findings coincide with the mode of injury, so that increases the likelihood that this is the "main" problem
Thread Starter
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Lead Driver
Joined: Mar 2004
Posts: 5,372
Likes: 108
From: Northern Indiana
Looks like you found a problem
As your rpms increase, so does the AC/interference, which can cause all kinds of things to act strangely.
I'd replace the alternator. The findings coincide with the mode of injury, so that increases the likelihood that this is the "main" problem
As your rpms increase, so does the AC/interference, which can cause all kinds of things to act strangely.
I'd replace the alternator. The findings coincide with the mode of injury, so that increases the likelihood that this is the "main" problem
Am I missing something? Test you sent me said below .5V. Am I brain dead or even at 2,000rpm reading am I still below that?
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
I glanced at your pics and thought the scale was showing .5 and 1.3
Well, that is NOT the case apparently. Glad you questioned it, sorry.
I'm remoted into a computer, tackling a virus on it at the moment and bounced back to check my email.
Doesn't meant the alternator is okay, just that Ripple isn't your problem
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
There are some alternator gurus on here (not me), hopefully they will chime in?
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Lead Driver
Joined: Mar 2004
Posts: 5,372
Likes: 108
From: Northern Indiana
Are you convinced that the alternator is the issue? I thought while running 14.6 was what the alternator and batteries were supposed to show?
Post Fiend
Joined: Mar 2015
Posts: 5,277
Likes: 32
From: Blairsville, Pennsylvania
In my experiences, 14.2v, 14.3v tops, once it crosses 14.5 and heads upwards to 15v, it's trouble.
That's why I'd like to hear from some guys who know these beast-er-nators better.