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69gladiator
AMC Apprentice Joined: Sep/15/2013 Location: stratford,ct Status: Offline Points: 242 |
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Posted: Dec/03/2022 at 9:39pm |
I have an 82 Cherokee with a 258 engine. I have had problems with the alternator (Delco) not charging unless I gun the motor. I thought that a bad engine ground was the culprit because it was so bad that the starter wouldn’t turn over. The ground issue was repaired and the engine turns over great. Some mechanic friends thought the poor ground may have contributed to frying the alternator. I replaced the alternator and the problem still persists. The wiring at the alternator appears ok. It seems like it’s behaving like a one wire hot rod set up. I’m stumped
Edited by 69gladiator - Dec/03/2022 at 10:08pm |
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rgsauger
AMC Nut Joined: Aug/17/2014 Location: Houston,TX Status: Offline Points: 311 |
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Belt tight? External or internal voltage regulator?
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Heavy 488
AMC Addicted Joined: Apr/27/2019 Location: In the Status: Offline Points: 3553 |
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Delco in that era is internal. Not getting triggered on.
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Mr_Roboto
AMC Apprentice Joined: Jun/12/2022 Location: Wisconsin Status: Offline Points: 221 |
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Few thoughts here:
1-A Chilton's/Haynes probably has a formalized procedure to test the wiring. 2-That aside, there are typically 3 connections to a 10SI Alternator. There's a field line, the power line and the sense line. The field line powers the coils, the power line is the output and the sense line runs through the gauge cluster (the light bulb, usually a resistor in parallel in case the bulb burns out) and to the alternator. 3-The field should see full voltage (I believe at all times) and be the thicker of the wires in the harness. The sense should see full voltage if disconnected from the alternator when the key is on. The power wire should see full voltage. 4-There may be some form of fuse, fusible link or other issue with the wiring. The field or perhaps (less likely IMO) the sense sounds like a good place to check in this case because it's "behaving like a 1 wire alternator." That means that the residual magnetism is possibly kicking on the alternator at higher RPMs. 5-Check the alternator voltage with a meter from the stud on the back to the ground. If it looks good check from the battery post to engine ground. If that looks good check from the hot to the negative post. If one of those drops voltage check its respective circuit. My money is on the field wire and a fusible link honestly. I will say I had an odd case once on my Astro with a CS130 (similar wiring system) where the dash light or wiring to the alternator shorted to ground. The light for the alternator stayed on even when the connector was unplugged and the alternator wouldn't ever kick on. May not be common but giving some food for thought. Went through 3 remans before I figured that one out! I guess we should also ask if you've added a bunch of load to this setup. If you're trying to hit an 8 pill CB amp or a 2KW stereo with EFI and some gnarly E-fans you may need to upgrade...............
Edited by Mr_Roboto - Dec/04/2022 at 10:45pm |
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FSJunkie
AMC Addicted Joined: Jan/09/2011 Location: Flagstaff, AZ Status: Offline Points: 4742 |
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If the alternator warning light DOES NOT turn on when you turn the ignition key to "run", that tells me everything I need to know.
You need to feed power to an alternator first before it generates power. The power feed to the alternator goes through the dash warning light. If the bulb burns out, the socket doesn't make contact, or anything else happens to create a break in that circuit, the alternator will not begin charging unless you rev the piss out of the engine. This is because the alternator rotor holds a slight amount of residual magnetism left over from the last time it operated that can sometimes generate enough power in the stator to power up the alternator by itself. Nearly all cars have some kind of backup power feed to the alternator should that bulb burn out or anything else go wrong in that circuit. AMC had a resistor on the wiring harness that ensured the alternator would always receive power...until about 1980 when they eliminated the wire. So...yeah...no backup. Without the backup, it goes like this: 1. Dash light burns out or the contacts corrode. In either case: no power feed to the alternator. 2. You do not have a warning light to tell you there is a problem, so you just keep on driving until your batter is dead OR you happen to rev the alternator high enough and it has enough residual magnetism to fire itself up. Stupid. Just stupid. I couldn't believe it until my own 1980's AMC's did it. I studied the wiring diagrams and confirmed it. Then I tested the harness and double confirmed it. It was one of the stupider things that AMC, a company that usually had smart engineering, did. |
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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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69gladiator
AMC Apprentice Joined: Sep/15/2013 Location: stratford,ct Status: Offline Points: 242 |
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I don't believe the later model FSJs had an alternator light only an ammeter. My 69 Gladiator does, It appears after looking at the wiring diagram that the brown wire from the alternator ends up at the ammeter .Could the ammeter be bad in the instrument cluster ammeter? I've got another cluster
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Mr_Roboto
AMC Apprentice Joined: Jun/12/2022 Location: Wisconsin Status: Offline Points: 221 |
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It may well be. That said, I'd probably start with metering stuff which is a lot easier than tossing a cluster in probably.
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Online Points: 6668 |
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Have you verified that the alternator is indeed charging the battery? There should be about 14V at the battery terminals with the engine running. You want about 12.6V between the battery terminals with the engine off. From the first post, I gather you are getting something out of the alternator, but you need to rev up the engine to start the alternator up. If you read some of the material billd has posted about alternators, you will see that different alternators have different stall speeds. i.e. they need to be above a certain RPM before they "start up". If you determine that your battery is being kept charged, I wouldn't worry all that much about having to rev the engine to get the alternator to start. It sounds like you solved the slow crank problem and the alternator was not the fault.
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69 Javelin SST BBO 390 T10
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69gladiator
AMC Apprentice Joined: Sep/15/2013 Location: stratford,ct Status: Offline Points: 242 |
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I have put a meter on the battery after I gun the engine and the alternator is putting out 14.2 volts . When I first got the truck my son drove around our section of town for a hour with the headlights on but never bumped the rpms and he killed the battery. I can live with charging issue but it would be nice if it worked.
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Trader
AMC Addicted Joined: May/15/2018 Location: Ontario Status: Offline Points: 6881 |
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Have you had the battery load tested? It could be a bad battery that just won't take a full charge.
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