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Confirm an alternator conclusion? |
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kensamc 
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Joined: Jul/29/2009 Location: Chicago Status: Offline Points: 393 |
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 Topic: Confirm an alternator conclusion?Posted: Nov/17/2009 at 2:21pm |
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This one is for my 86 Grand W with the 360 . IFSJA had several posts about charging gremlins.... followed everything to the letter and just last night got stranded with my 2 year old on board. They conclude that the fusible link is the weak link, BUT I had the prescribed jumper wire running from alternator to the positive post side of the solenoid on the fender. No shorts show by metering from positive to block with the neg terminal disconnected. If I disconnect the positive terminal with the engine running the alternator meters 15 volts. Once reconnected to the battery, it meters anywhere from 11.73 to 12.52 volts ... never higher. Already new battery, new alternator(rebuilt) and the jumper wire around the fusible link. This has to be an intermittent alternator, right ?? If I have to take the wife's car to work, she'll never let me forget it..... |
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1986 Jeep Corp Grand Wagoneer
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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: Nov/17/2009 at 2:39pm |
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Depending on exactly what you disconnected and when and run it, if there wasn't something amiss before, good chance there is now.
One should never run with anything disconnected, regardless of what you read on the self-help sites.
Diodes and regulators can be blown that way.........
Rebuilt alternator doesn't necessarily mean good..........
With the engine NOT running, what is battery voltage?
With the engine RUNNING and everything connected, what is the voltage at the battery?
GM alternators have a tab you can short to bypass the regulator (assuming GM alternator here) what do you get if you short that tab?
Ignore ANY advice on disconnecting wires and running it with things disconnected.................. and NEVER disconnect anything with the engine running......
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kensamc
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Posted: Nov/17/2009 at 2:49pm |
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Bill
Aside from fear of frying myself, I worried about disconnecting it for the alternator's sake as well, but was at my wits end. It is a 10si .... knew nothing of a tab to short on that ... This is my third battery since replacing the alternator. Now that it has been run down once, it metered 11.73 when I limped home. Also what it metered this morning after sitting all night. With the engine running and everything hooked up, this morning it read 12.23 The check for short was of course, with the engine off. Checked both between pos and block and between positive cable and battery terminal. I half assumed I may have lost the alternator when the last battery died, because I understand it is not the alternators job to fully charge a dead battery, but I managed a quick jumpstart and it metered 12.9 volts, and off I went. 11.73 is too low for the battery I know... 2 week old Diehard too Thanks for the prompt reply BTW |
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1986 Jeep Corp Grand Wagoneer
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kensamc
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Posted: Nov/17/2009 at 2:50pm |
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Not that it makes it a lot better to do, but my Dad was a car guy and a brilliant diagnostician .. wish he was still around...
And some of my bad troubleshooting habits came from the family tree ....
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1986 Jeep Corp Grand Wagoneer
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billd
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Posted: Nov/17/2009 at 9:49pm |
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The problem is that some old-skool troubleshooting came from the older technology - generators and alternators with dual circiuit regulators - cutout relays, etc.
Check out this image - there's a D-shaped hole. Inside that hole is a tab. Put a small screwdriver in there and ground the tab to "full-field" the alternator (touch tab and alternator case at same time) - it should hike the voltage up to 15-16volts. Don't hold it there and don't run lights or radio, etc. while doing this. If it doesn't whine and start charging heavy, there's an alternator issue. If it does, a regulator issue (or wiring issue).
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kensamc
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Posted: Nov/18/2009 at 8:22am |
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I can try that, though the alternator is awfully close to the exhaust... have a few burns to prove it so far ...
Does the fact that it went to 15 volts plus when disconnected from positive imply a problem already ? The info on IFSJA made sense after all I went through ; but having bypassed (actually augmented) the fusible link already there isn't much left but the alternator itself.... As you said, rebuilt doesn't mean good...
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1986 Jeep Corp Grand Wagoneer
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rockrash
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Joined: Dec/23/2009 Location: Georgia Status: Offline Points: 34 |
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Posted: Dec/26/2009 at 8:28am |
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A delco alternator can be pulled down by a short or poor ground in the system. Has your amp/voltage meter been jumping around on rough roads or perhaps when you put on your turn signals??? Check for loose or hanging wires....especially any butt splices that can have weight pulling on them. A wire that looks fine with a connector inline can cause the fault that you mention. Any local parts house can usually test your alternator....many go through a detailed test of diodes, regulator etc.
Pull it and have it tested.....but on a vehicle that old, chances are it is a wiring issue.
I have an ol' Blazer that gave me the same fits till i began securing wires and sealing connections. After that was done it seldom sees lower than 14v running lights, heat, and wipers.
Good luck.
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kensamc
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Posted: Jan/05/2010 at 1:50pm |
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AFter all the hunting and goofing, it proved to be the regulator in the alternator.
I did upgrade to the Powermaster 140 amp AND ran the secondary charging line as detailed on IFSJA. First time since I have owned the GW that it showed anything north of 13v on the voltmeter in the cab, and it meters at the battery at a beautiful 14.2. I honestly don't know, but assume that AMC cars used the same alternator at the end of their days ???? But probably not the fusible link.... Did or did not, I can say that a bigger , better alternator and the secondary charging line is a must for the late model Grand Wagoneers. Thanks all for kicking this around |
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1986 Jeep Corp Grand Wagoneer
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billd
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Posted: Jan/05/2010 at 2:18pm |
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AMC used Delco in the 80's, although they used others as well.
Depends on the options and if it was considered "heavy-duty" or not. Both of my Eagles, with A/C and all the trimmings, have Delco alternators factory on them. (and I'll rebuild them as well) The Jav will forever be Motorola, or at least as long as I own it. |
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poormansMACHINE
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Charter Member Joined: Jun/28/2007 Location: Shoemaker-Levy9 Status: Offline Points: 12302 |
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Posted: Jan/05/2010 at 7:12pm |
A fuse of some sort should be present be it a fusible link or a physical fuse. |
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kensamc wrote: