Re: HOW TO TROUBLESHOOT ALT/VR
[Re: frank]
#1430414
05/04/13 08:47 PM
05/04/13 08:47 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Set the throttle on fast idle. Take off the green wire field terminal connector off of the alt field male spade terminal & ground the alt spade terminal (not the wire you removed from it) for 3 seconds max & if this full fielding makes the alt max charge then all is good in the 'hood except for (1) the green wire from the alt to the reg "you checked it" (2) reg ain't grounded "I'm thinking it is" (3) reg is fried. I believe you said the alt/reg are both getting switched 12V on the blue wire. Have all bulbs/accessories OFF when full fielding & I like to run an 8 ga or larger jumper from the alt to the batt when doing this. A bit picky but that's me. Holler how it goes.
live every 24 hour block of time like it's your last day on earth
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Re: HOW TO TROUBLESHOOT ALT/VR
[Re: frank]
#1430416
05/04/13 09:12 PM
05/04/13 09:12 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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Check the voltage at the alt "batt" stud. Just to be sure jump from the green wire spade to the batt neg post rather than to the alt case but so far it's looking like the alt is bad. Might jump fire from the batt positive post to the blue wire spade field terminal on the alt just to be sure the field is getting fed full voltage
live every 24 hour block of time like it's your last day on earth
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Re: HOW TO TROUBLESHOOT ALT/VR
[Re: frank]
#1430418
05/04/13 09:40 PM
05/04/13 09:40 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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"For future reference" The 8 ga wire was to go from the alt "batt" stud to the battery positive post just so the full voltage when full fielding would go directly from the alt to the batt rather than the circular route thru the problematic bulkhead but no big deal. yes the alt is putting out. If the green wire from the alt field to the reg side terminal has continuity and the reg is grounded then yes the reg is fried. The blue wire at the alt was hot since full fielding it by grounding the green terminal made it charge & we're assuming that the blue wire at the reg top terminal has fire at the same time
live every 24 hour block of time like it's your last day on earth
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Re: HOW TO TROUBLESHOOT ALT/VR
[Re: RapidRobert]
#1430421
05/04/13 10:43 PM
05/04/13 10:43 PM
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Joined: May 2003
Posts: 6,569 Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,569
Downtown Roebuck Ont
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Before you dash off to the parts store, clean up the area where the regulator bolts to the firewall or better yet, run a ground wire to the regulator just to rule out a bad regulator ground as the problem. Another obscure cause might be a bad ammeter connection. My father had a 75 Gran Fury when I was growing up that would fail to charge after replacing alternators and regulators. He blamed the "new fangled" electronic regulators as the culprit and switched it back to the mechanical style regulator and it never gave another minutes trouble. Fast forward a few years and one day when he was into the dash to change something, found that the ammeter connection was IIRC just a push on friction connection and it was as green as grass. Cleaned it up and the electronic regulator worked fine. The only thing we could figure was that the regulator saw the resistance from the green corroded connection as a full charged battery and never turned on the alternator. Kevin
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Re: HOW TO TROUBLESHOOT ALT/VR
[Re: RapidRobert]
#1430422
05/05/13 12:23 AM
05/05/13 12:23 AM
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Joined: Feb 2003
Posts: 2,138 tucson az
frank
OP
top fuel
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OP
top fuel
Joined: Feb 2003
Posts: 2,138
tucson az
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Quote:
was it the reg?
No. Put a new one on and same gig.
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Re: HOW TO TROUBLESHOOT ALT/VR
[Re: frank]
#1430423
05/05/13 04:20 AM
05/05/13 04:20 AM
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Joined: Jul 2008
Posts: 610 Boise
Moparteacher
mopar
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mopar
Joined: Jul 2008
Posts: 610
Boise
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Have you tested the battery? A faulty battery may not take a charge and will confuse the VR which monitors battery voltage. Have the battery properly tested after it is at least 50%charged with a disconnected standing charge of 12.2V or higher. Confirm your battery connections are clean and secure. Confirm the VR and alternator is grounded with clean, secure fasteners. Bypass the dash-mounted ammeter by running a heavy jumper wire from the alternator positive post to the battery positive post and then check high idle voltage, 13.2V-14.8V give or take a 1/10th. Confirm continuity on the green field wire between the VR and the alternator with an ohm-meter while both ends are unplugged. Should be less than .5 ohms. Wiggle the wire harness while testing to check for concealed breaks in the wire.
FYI: Your VR supplies a ground for the alternator field. It's a cycling switch. When the green field wire is grounded through the VR the alternator's magnetic field grows and produces an increase in voltage output. It connects and disconnects the ground rapidly to regulate the strength of the field. The VR monitors battery voltage that's coming through the ignition switch to determine the duty cycle of the grounding of the alternator field. When you full-field the alternator your duty-cycle is 100% and the alternator produces maximum output in voltage and heat.
The power for the field also comes through the ignition switch.
The alternator output goes to the ammeter in the cluster to swing the needle and then goes to the battery usually by way of the post on the starter relay. From there the current is distributed to the battery, starter solenoid, and fuse box for further distribution. You can check this wire by either by bypassing it or performing a voltage drop test.
You can perform a voltage drop test on any positive or negative circuit when current is flowing, or supposed to be flowing. With the engine at high idle, turn headlights on to load the alternator. Connect a digital voltmeter (don't use one with a swinging needle, analog) between the battery positive post and the alternator output post. DVOM common lead (black) on the battery positive and red lead on the alternator positive post (positive to positive). The voltage drop should read no greater than .5V. (half a volt). You can do the same with the ground. Alternator case to battery negative post (ground to ground), again expect a low number of .1V to .3V. High numbers, above .5V, mean there is an open or high resistance in the circuit. Older cars may see as high as .8V and be OK.
Let us know what you find.
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Re: HOW TO TROUBLESHOOT ALT/VR
[Re: RapidRobert]
#1430428
05/07/13 11:49 PM
05/07/13 11:49 PM
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Joined: Feb 2003
Posts: 2,138 tucson az
frank
OP
top fuel
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OP
top fuel
Joined: Feb 2003
Posts: 2,138
tucson az
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I'll try the original mechanical regulator tomorrow. BTW I bypassed the amp gauge this last test. Same results
Last edited by frank; 05/07/13 11:51 PM.
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