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Starts and completely dies |
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Hayes89
AMC Apprentice Joined: Oct/06/2017 Location: Long beach Status: Offline Points: 59 |
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Great information bud thank you I'm going to try all of that out as soon as I get back home. It sounds easy enough 😉
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6670 |
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If I read your first post correctly, the battery quickly discharges while the car is running. A shorted winding in the alternator could produce this symptom. A failed regulator wouldn't cause the battery to discharge that quickly, IMO. A quick way to verify a failed alternator is to disconnect the alternator output wire (the heavy gauge cable) and tie it off so it doesn't contact the body of the car. With a fully charged battery, the car should run for some time. This assumes that the batteries you are using are in good condition. I would recommend getting at least one of them load tested just to be sure.
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69 Javelin SST BBO 390 T10
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Hayes89
AMC Apprentice Joined: Oct/06/2017 Location: Long beach Status: Offline Points: 59 |
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So that would be the thick power cable coming from the starter solenoid to the alternator correct? So I have another red wire on it I think it's for the alternator bulb light
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bigbad69
Supporter of TheAMCForum Joined: Jul/02/2007 Location: Ottawa, Ont. Status: Offline Points: 6670 |
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Yes, the battery + and alternator output go to the solenoid input. I don't have a wiring diagram for 72, so I don't know exactly what that third wire is for. Leave it connected as it is unlikely to be the cause of your problem. I will quote myself:
Does the battery discharge with the engine off? That is a clue.
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69 Javelin SST BBO 390 T10
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Regamble1969
AMC Apprentice Joined: Dec/01/2021 Location: Boise Idaho Status: Offline Points: 204 |
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I pretty much agree with this. Like I said, one time 20+ years ago and I wasn't the tech on the car so my memory of that particular case is a bit foggy. And that's my understatement of the day. What bigbad69 and I are pretty much getting at is to break it down in small diagnostic pieces. 1. Doe the battery drain in the car with the key off? A. Yes - there is a huge drain on the non-switched side of the electrical system. This could still be the primary wire on the alternator. Disconnect it and check again. B. No - move to next step. 2. Does the battery drain in the car with the key in the run position but not started? A. Yes - there is a huge draw on the switched side of the electrical system. (Highly unlikely scenario but simple to test so do it anyway). B. No - move to the next step. 3. Does the battery drain with the car running but the alternator disconnected? A. Yes - something on the VR circuit. (Grossly and wildly unlikely... but not impossible) B. No - the alternator likely has a shorted winding or metal contact somehow. Bad alternator. These are the steps I would take and questions I would try to answer. Bigbad69 also mentioned getting a battery load tested, which would be a good idea if you can. It's always good to know what you're starting with.
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