Electrical problem 72 XLT
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New User
Joined: Jan 2003
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From: North Seattle
Electrical problem 72 XLT
I am having a pulsing of lights and a slight whine at low idle. Truck starts and runs fine. I have the folowing new or rebuilt equipment.
New positive and negative battery cable
New Ford battery
New old-style large regulator
Rebuilt alternator
New starter
New fan belt
All wiring has been cleaned up with all new connectors
At night you can see the dash lights and headlights pulsing. Not a lot, just enough to notice. All the new parts are less than a month old. If I increase idle the pulse goes away. As my Ford ammeter guage does not work (who's does) I cannot tell if I am dipping into discharge territory. The slight whine makes me suspect the rebuilt alternator, but the pulsing of energy makes me feel that it would be a regulator issue. All connections are tight and battery terminals are secure and tight.
Anyone's thoughts before I start ripping it apart again?
George
Seattle
New positive and negative battery cable
New Ford battery
New old-style large regulator
Rebuilt alternator
New starter
New fan belt
All wiring has been cleaned up with all new connectors
At night you can see the dash lights and headlights pulsing. Not a lot, just enough to notice. All the new parts are less than a month old. If I increase idle the pulse goes away. As my Ford ammeter guage does not work (who's does) I cannot tell if I am dipping into discharge territory. The slight whine makes me suspect the rebuilt alternator, but the pulsing of energy makes me feel that it would be a regulator issue. All connections are tight and battery terminals are secure and tight.
Anyone's thoughts before I start ripping it apart again?
George
Seattle
Posting Guru
Joined: Jun 1999
Posts: 2,415
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From: Comox Valley, Canada
Electrical problem 72 XLT
This is my best guess 
The old style regulator is made up of relays and points....so maybe it just isnt regulating the voltage "fast" enough at idle.
The newer flat regulator is electronic....all that cool solid state stuff that "baffles" my mind It may work a little better....but I cant see running out and buying one just to fix a small light fluctuation problem at idle
Can you maybe turn up the idle a small bit??
The old style regulator is made up of relays and points....so maybe it just isnt regulating the voltage "fast" enough at idle.
The newer flat regulator is electronic....all that cool solid state stuff that "baffles" my mind
It may work a little better....but I cant see running out and buying one just to fix a small light fluctuation problem at idle Can you maybe turn up the idle a small bit??
Post Fiend
Joined: Apr 2002
Posts: 7,157
Likes: 1
From: Central Kali
Electrical problem 72 XLT
Get one of the solid state voltage regulators, short cover. I used the older style for decades and am still surprised that they worked. Install a voltmeter and you will know what is going on.
Install a voltmeter and you will know what is going on.
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Electrical problem 72 XLT
If everything is less than a month old, I'd take back that alternator and exchange it. They're not supposed to whine unless it's putting out some serious current. Maybe you popped a diode, that will make it whine too and cause your lights to flicker at idle. You can't see the flicker above idle cause it's flickering too fast to see. Batteries don't like to see that flickering voltage, it's an AC signal not being rectified by a shorted diode on that phase of the windings. Anyway, I'd exchange it under warranty.
Barry
Barry
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From: North Seattle
Electrical problem 72 XLT
Took the alternator off and had it tested at the parts store. They said it was dead. But then after trying 5 other alternators on the shelf which all also read as dead they sent me to another store. The other store tested the replacement alternator and it was putting out 13 volts. I took it home and hooked it up. Guess what, same pulsing lights at idle.
So, I drove the truck to the parts store and they put an analyzer on the truck while it was running. Battery read good, alternator read good and output from the old style regulator read good. It was sort of a pass/fail instrument and not one that would read a voltage surge though. There was no guage, just a digital read out.
They suggested that I might have a loose ground somewhere.
I had replaced the old regulator to be proactive. When I took the old one off I did notice that it was the new-style regulator that is less large than the old style. I am beginning to think I should go exchange the regulator for a new-style one.
Anyone's thoughts?
So, I drove the truck to the parts store and they put an analyzer on the truck while it was running. Battery read good, alternator read good and output from the old style regulator read good. It was sort of a pass/fail instrument and not one that would read a voltage surge though. There was no guage, just a digital read out.
They suggested that I might have a loose ground somewhere.
I had replaced the old regulator to be proactive. When I took the old one off I did notice that it was the new-style regulator that is less large than the old style. I am beginning to think I should go exchange the regulator for a new-style one.
Anyone's thoughts?
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Electrical problem 72 XLT
So do you have the same alt. on there that was whining?
Put a voltmeter across the battery and switch the function to read AC only to read any ripple voltage.
Barry
Put a voltmeter across the battery and switch the function to read AC only to read any ripple voltage.
Barry
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Joined: Jan 2003
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From: North Seattle
Electrical problem 72 XLT
No, new alternator. No whine. Just this pulsing at low idle.
I did check the ground strap and it seems to be fine. All the connections seem fine.
Only thing I have not replaced is the terminal that the alternator wire, battery wire, starter wire all attach to.
I do not have a voltmeter unfortunately.
Thanks
George
I did check the ground strap and it seems to be fine. All the connections seem fine.
Only thing I have not replaced is the terminal that the alternator wire, battery wire, starter wire all attach to.
I do not have a voltmeter unfortunately.
Thanks
George
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Thread Starter
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Joined: Jan 2003
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From: North Seattle
Electrical problem 72 XLT
Well, I got a voltmeter and it was showing about 14 volts to the battery with a definite pulse. Not a large one, but one none the less.
Took the old-style regulator off and exchanged for a new electronic (smaller) style regulator and pulse is now gone.
So much for sticking to original style parts eh!
Thanks for the help Gents!
George
Seattle
Took the old-style regulator off and exchanged for a new electronic (smaller) style regulator and pulse is now gone.
So much for sticking to original style parts eh!
Thanks for the help Gents!
George
Seattle
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New User
Joined: Jan 2003
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From: North Seattle
Electrical problem 72 XLT
Actually, it is an old dwell meter that I got from an auto parts store in the early 80's. Was tickled it still worked. I had forgotten that it had a volt meter on it.
Glad all is well, now I just have to figure out why my brand new front brake drum setup is pulling to the left.
George
Seattle
Glad all is well, now I just have to figure out why my brand new front brake drum setup is pulling to the left.
George
Seattle
Elder User
Joined: Jun 2002
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From: Elizabeth City, NC
Electrical problem 72 XLT
Working on Electronic's, anytime I get a problem that seems to be really weird I check the output of the power supply. AC ripple at the output of a DC power supply can cause some real head scratching faults!
Post Fiend
Joined: Apr 2002
Posts: 7,157
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From: Central Kali
Electrical problem 72 XLT
Glad you got it fixed. There are good deals on digital voltmeters out there for around $20. I got everything from a $5 Harbor Freight special to a $300 Fluke. I hate to get the Fluke greasy. 
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