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Eagle Alternator Excitation Question |
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FSJunkie 
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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 Topic: Eagle Alternator Excitation QuestionPosted: Aug/18/2018 at 2:45am |
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Do Eagles have any way to feed power to the number 1 terminal of the alternator other than through the alternator warning light? Power must be fed to this terminal for the alternator field to excite and cause the alternator to begin charging. If the bulb fails, the alternator will not charge. Most earlier AMC's have a resistance wire in their wiring harness to supply the excitation voltage to the number 1 terminal if the light fails to conduct (burned out). I see no mention of Eagles having this backup feature in the service manual and no indication of it existing in the wiring diagram. |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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vinny
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Joined: Jan/05/2012 Location: Calgary Status: Offline Points: 2837 |
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Posted: Aug/20/2018 at 7:58pm |
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I don't know about original equipment but some people parallel in a resistor when changing over to the GM alternator. The alternator light in my car has been fine for as long as I have owned it so I'm not going to worry about it.
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FSJunkie
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Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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Posted: Aug/21/2018 at 3:45am |
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My Hornet came with a 10SI as original equipment and it has a resistor wire in parallel with the indicator light in case the light fails. Earlier AMC's with Motorola alternators have a resistor parallel with the light too. It's a backup safety. I'd be surprised if Eagles don't have some kind of backup feed for the alternator excitation. The alternator will stop charging if the light fails! I don't know. I have the entire dash and interior torn apart right now to decontaminate it of nuclear fallout (products of mouse infestation), so I'll surely find out soon enough. |
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1955 Packard
1966 Marlin 1972 Wagoneer 1973 Ambassador 1977 Hornet 1982 Concord D/L 1984 Eagle Limited |
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vinny
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Joined: Jan/05/2012 Location: Calgary Status: Offline Points: 2837 |
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Posted: Aug/21/2018 at 5:47am |
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Some years back I bought a 66 Chev truck that had been sitting for years in a field with rust holes in the floor. There was nothing left of the seat except wire and the heating ducts were packed full of the seat material. Gopher crap was up to an inch deep on the floor but no damage to the panel or wiring. It took a lot of hosing to get all that crap and 22 shells cleaned out. Apparently in previous years when the truck was running the guy would drive around with dog on the hood pointing and he would shoot gophers. In the end they got their revenge.
I put a 10si in that truck to do away with the regulator but did not parallel in a resistor. I put a CS130 which supposedly should have a resistor in the Rambler and it has been working fine without it for about three or four years now. If I get some spare time maybe I'll wire them in. Good luck with your clean up project. |
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Fluffy73
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Joined: Nov/21/2007 Location: Castlegar, BC Status: Offline Points: 3059 |
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Posted: Aug/21/2018 at 2:38pm |
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I thought 10SI's were self-exciting?
The one in my old SX/4 used to need a quick stab of throttle before it would start charging. If you started it warm without touching the gas at all, and the engine began running at curb idle, it would not charge until you gave it 1,500 rpm or so. Interestingly enough, I learned this through the use of a voltmeter. At no time did the light on the dash come on to indicate this. |
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I am genetically incapable of being Politically Correct.
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Aug/21/2018 at 6:43pm |
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NO GM never made such a system.
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Aug/21/2018 at 6:55pm |
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No, "most earlier AMCs" do NOT have a resistance wire in their harness to supply the excitation voltage...... It's the IGNITION feed that does this and this was added only in the mid-1960s. The very first alternator systems used by AMC used the light, and a separate resistor mounted on the fender. It was literally a ceramic resistor like an ignition ballast resistor, about 75 ohms. I have a NOS one, still in the box. Then AMC went to a replacement regulator that got rid of that resistor and took the feed from the ignition system in case of bulb failure. And no, there's the bulb and that's it. Drivers are supposed to turn the key on and watch for the oil pressure AND alt light to come on then crank to start it and if the light doesn't come on, they are to go in for service.. Seriously. It's rare the bulbs ever burn out, I've not replaced one in decades, never had one go bad in my own car, because there's no load, they are on only when the engine isn't running and the key is on, or if the alt doesn't charge. So it's used something like a fraction of a percent of the time the driver is in the car - not much time to burn it out.
No GM alternator is "self-exciting". Most will kick with a high rev IF the excitation circuit is dead, but it's not by design at all, not in any way, shape or form. As I've preached here for a decade, GM never released a "one-wire" system nor any that "self excite", that's done by third parties or people who don't know any better. It's the regulator that some companies put in them to make them that way - but it's not a GM design. |
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billd
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Forum Administrator Joined: Jun/27/2007 Location: Iowa Status: Offline Points: 30894 |
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Posted: Aug/21/2018 at 7:02pm |
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So how often does a light fail? RARE, and I mean RARE. The driver is supposed to check the lights when starting the car. I'm serious. They are to see if it comes on or not prior to starting. A bad bulb is EXTREMELY rare as a problem with charging, can't say I've seen that happen in the last 4 decades.
The system won't stop charging, but it WILL take a smack of about 1500-2000 RPM to kick it in. So all is not lost - it will kick in after it spins up FAST enough to let the teeny teeny bit of residual magnetism left in the rotor causes enough output to feed the rotor via the output of the alternator. AMC did NOT have a parallel resistor with the Motorola systems. Sorry, no, they did not - Motorola systems were excited by the current through the bulb into the regulator, or, the IGNITION feed. You can go see that in the wiring diagrams. Check from about 65 or so and later into 74 - - NO resistor. None. Only the VERY early Motorola systems had a resistor - the TVR series of regulator had three connections and used a resistor on the fender. Once they changed to the R2 series, they took away that resistor and used the bulb via the orange wire, and the backup system was the IGNITION feed. There was no parallel resistor in the days of Motorola, and the backup was not a resistor at all but was the feed to the ignition COIL. (via YELLOW wire) Edited by billd - Aug/21/2018 at 7:08pm |
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purple72Gremlin
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Charter Member Joined: Jul/01/2007 Location: Illinois Status: Offline Points: 16611 |
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Posted: Aug/21/2018 at 7:42pm |
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billd
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Posted: Aug/21/2018 at 8:00pm |
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Exactly right, Tom - it's the bulb check phase. Any equipment operator is supposed to pay attention, but these days, driving has been dumbed down soooooo much.
The early owner manuals for some cars even mentioned bulb check etc. Today, the computer does this for you - hey, dummy, you have a burned out bulb! But people who don't pay attention will complain - the car isn't working right, it won't charge. Well, did the light come on when you turned the key on? Dunno, I never look at the dash, I finish putting on my makeup when pulling out of my garage.
Bottom line - learn the car, do the bulb check and if the bulb does NOT come on when you turn the key on, it's supposed to go to the dealer (well, years ago) - today, fix the bulb! |
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Fluffy73 wrote: