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70 AMX alternator help |
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Cookie 
AMC Apprentice 
Joined: Mar/17/2020 Location: Sanford, NC Status: Offline Points: 67 |
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 Topic: 70 AMX alternator helpPosted: Apr/01/2020 at 7:27pm |
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ORIGINAL ISSUE:
So I was having starting issues and replaced the battery, spark plugs and wires and got it running. NEW PROBLEM: I think the alternator is shot because I have no increased voltage at the battery when the car is running. REAL PROBLEM: This car is new to me and I don’t know everything that was done before, the electrical system is pretty out of whack.(no gauges work and there is random wires disconnected all about) Now the main issue I am having is something I noticed that does not look right to me. The way the alternator is wired up seems odd. And on top of it all I have no idea what type of alternator it is to try and research more. Any help or direction will be greatly appreciated.    In this one, the green arrows show a black and a red straight from the battery and into the passenger side firewall. Haven’t found out where they go yet. The blue arrow is a connection from the battery to the back side of the alternator, shown in the first picture. Focusing more on the blue arrow and the alternator at this point, is that wired correctly? And does anyone have an idea on what type of alternator this is?
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1970390amx
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Joined: Jul/11/2008 Location: colorado Status: Offline Points: 3314 |
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Posted: Apr/01/2020 at 7:43pm |
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It looks like a general motors alternator, some are sold as a one wire alternator for easy installation. They dont work all that great,esp. at idle. Are there more than one wire going to the alternator?
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1970 390 4speed Bittersweet shadow mask AMX
1970 Amx missing most everything, or in a box |
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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: Apr/01/2020 at 7:50pm |
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Yikes, direct from alternator to battery? Unsafe as heck.
Someone yanked out the original system and put in what looks like a Delco alternator. Again hard to tell from the pics, but may be wired as a tractor or some industrial equipment with a single wire.
Ugh, I hate that when people who don't know how to fix things toss on one of those wired that way because they don't want to bother doing it right. IF it's Delco and if it's wired that way, bypassing any system voltage sensing and wired "single wire", then you may have to rev it as high as 2,000 RPM before it kicks anything out because they removed the excitation circuit - meaning it won't start charging at idle, it has to be rev'd first. It's a hack. Period. The way to check GM alternators with internal regulators no matter how they are wired is by using a small screwdriver through the D-shaped hole and grounding the regulator tab that's inside the alternator. That should cause it to charge at max output. If that doesn't do it, then the alternator has problems. If that does it, the regulator is bad. In any case, wiring output direct to battery with no safety like a fusible link, etc. can lead to problems - like wiring melting, etc. |
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Cookie
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Joined: Mar/17/2020 Location: Sanford, NC Status: Offline Points: 67 |
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Posted: Apr/01/2020 at 8:03pm |
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Billd,
“ In any case, wiring output direct to battery with no safety like a fusible link, etc. can lead to problems - like wiring melting, etc. ” This is exactly what I was thinking. So if I rip this guy out, what are your recommendations on the way ahead? Is going with the GM route the best? I already reviewed your other posts about the install, seems straight forward, I just don’t know what from “stock” capabilities I have at my use, and what has been changed.
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Cookie
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Joined: Mar/17/2020 Location: Sanford, NC Status: Offline Points: 67 |
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Posted: Apr/01/2020 at 8:05pm |
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And I just confirmed the only wire going to the alternator is the red one directly from the + side on the battery
Edited by Cookie - Apr/01/2020 at 8:08pm |
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Mopar_guy
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Joined: Jun/07/2009 Location: Ohio Status: Offline Points: 4828 |
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Posted: Apr/02/2020 at 8:07am |
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Yes it's a GM 1 wire. It can be fixed most likely. If you stay with that, I would put a 120 or 130 amp fuse on that red output wire to protect the car. Seeing what you're posting, for now get that one fixed and put a fuse in it and keep moving forward. That will help make it drivable again without a lot of hassle. I personally don't like those but for what you have there's nothing wrong with using it.
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mbwicz
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Posted: Apr/02/2020 at 8:54am |
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If you do want to replace the alternator, you should go to an aftermarket vendor. Ask for one that is converted for a 1 wire application. If you go to NAPA (or whatever local auto parts store), they will give you a factory GM alternator that will require additional wires, as described by BillD above.
It has been a common thing to have a '1 wire' alternator for the aftermarket crowd (street rod, show car) because they are easier to install and have less wires to look 'cluttered'. So look for powermaster or someone like that (or search at Jegs/summit) for a 1-wire GM/Delco alternator. And pick up an inline fuse, as suggested, at the same time. Bad things happen when wires melt. Once you get the car running/driving see how things go. If you continue to have electrical gremlins, it may be best to rewire the car with an aftermarket harness (since you aren't stock anyway). But get it running and see how things go. Mike |
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1970 AMX, one step forward, one step back. Both steps cost time and money.
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6PakBee
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Posted: Apr/02/2020 at 10:11am |
There are few things more frustrating than working on a car's electrical system that "Tommy Tinker" has had his hands on. You have to get a TSM with the electrical schematic and go through it wire by wire. This systematic approach is critical. The "poke and hope" approach typically only leads to more frustration. I feel for you as I have been there, and done that, more times than I want to admit. Good luck. |
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Roger Gazur
1969 'B' Scheme SC/Rambler 1970 RWB 4-spd Machine 1970 Sonic Silver auto AMX All project cars. Forum Cockroach |
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Cookie
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Joined: Mar/17/2020 Location: Sanford, NC Status: Offline Points: 67 |
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Posted: Apr/02/2020 at 4:08pm |
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Good advice from everyone above, can’t thank you guys enough.
I may try and get this one working using some research I’ve found on “fixing” the aftermarket GM 1 wires. If not then I’m going to get a new one. (Probably stick with 1 wire for the time being) But before anything I’m going to put a fuse in-line on that wire going to the battery. And just so I am tracking correctly, that wire is an output from the alternator to charge the battery correct?
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Trader
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Posted: Apr/02/2020 at 4:28pm |
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The one wire charges the battery and supplies power to the vehicle when running. It's other jobs are to also supply power to the alternator exciter and internal voltage regulator.
The other connection is the case to ground on the engine - that has to be good! A properly functioning one wire or any alternator should be reading 14.2 to 14.4 VDC when the vehicle is running - at any RPM.
Edited by Trader - Apr/02/2020 at 4:31pm |
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Cookie wrote: