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best electrical question EVER

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Old Nov 14, 2020 | 09:08 AM
  #1  
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best electrical question EVER

1990 e 250 4.9 new alt new battery excellent wiring. while engine is running and nothing no lights or heater or any drain everything is great. turn things on engine runs like crap miss fires bucks and acts stupid. no AC ripple from alt. 14.4 stays constant. today i was replacing idler pully and started engine with no alternator belt to hear the difference in sound from bad pully bearing. this is when i found out that i could run any and all accessories without causing a misfire. voltage was 11.5ish of course belt back on and ran engine with accessories on and back to misfires and crap. there is a capacitor on the coil pack to reduce noise that i have not checked or replaced but that's it. crazy
 
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Old Nov 14, 2020 | 12:17 PM
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Why did you replace alternator? Was the issue there with your old alternator as well?
 
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Old Nov 14, 2020 | 01:27 PM
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Originally Posted by jtab
Why did you replace alternator? Was the issue there with your old alternator as well?
good question , the old one had an external voltage regulator that got damaged when i was changing the engine. the new one has internal and is a better alternator.
 
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Old Nov 15, 2020 | 01:20 AM
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I would have to say you just proved that it is a problem with you alternator, or in the hook up? You say no ripple on output? How did you read this? What did you do with the old external voltage regulator and wiring? IS the new alternator a one wire? OR 3g upgrade? Or ?? If you have no issues without the alternator running and issues when its running I say it's in that factor someplace.
 
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Old Nov 15, 2020 | 10:10 AM
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Originally Posted by OhioFordFarm
I would have to say you just proved that it is a problem with you alternator, or in the hook up? You say no ripple on output? How did you read this? What did you do with the old external voltage regulator and wiring? IS the new alternator a one wire? OR 3g upgrade? Or ?? If you have no issues without the alternator running and issues when its running I say it's in that factor someplace.
i think it is the alternator also. the original had an external voltage reg that got damaged hen i changed engines. this new one came from an alternator shop they ordered it for me it is a 130 amp unit with internal reg. i went back to the shop and had them test for a bad diode and they hooked up their tester and had me turn on everything i could then brought up rpms to around 2000 i have done the same test at home with a fluke on AC and get 0 ac volts.
 
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Old Nov 16, 2020 | 10:11 AM
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Sounds like something is going to ground that is causing your poor engine performance.
As you turn on each accessory is there a specific point where the engine runs bad? Did the bench test show the new alternator was good? Is everything plugged back in after the engine swap? Kind of a can of worms!
 
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Old Nov 16, 2020 | 12:23 PM
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update went back to alternator shop with alternator in hand .when they tried to test it they cloud not get the belt tight enough under load so now they are tearing it apart.
 
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Old Nov 16, 2020 | 12:58 PM
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Too may times over the years I have installed a "new" starter or alternator only to find it did not work. Usually a remanufactured.
So recently did an alternator for a friend (PITA) and before I left the auto parts store (NAPA) I requested them to bench test it. Guy was a bit of a dick about it saying "why? It's brand new" so I told him because it's better to know before I install their "life time guarantee" than later... It bench tested fine and I said Thank You. Was in a Honda.

Never leave the store without bench testing the new one!
 
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