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Altenator wont charge battery

Tiny
STORMJONES
  • MEMBER
  • 1991 FORD MUSTANG
  • 185,000 MILES
So I just replaced the alternator in my 5.0 mustang but it still won't charge the battery does anyone know what it could be? Wiring?
Tuesday, March 13th, 2012 AT 9:47 PM

40 Replies

Tiny
SATURNTECH9
  • MECHANIC
  • 30,870 POSTS
Most likely its a bad voltage regulator do you have a multimeter to do some testing?
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Tuesday, March 13th, 2012 AT 9:53 PM
Tiny
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Yes I do I just don't know where that is
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Tuesday, March 13th, 2012 AT 10:05 PM
Tiny
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Get a meter and we will do some testing.
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Tuesday, March 13th, 2012 AT 10:20 PM
Tiny
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Okay I have the test light but I just did a t5 swap in it and don't remember if I hooked a ground back up that was connected to a transmission bolt. Is there a ground there?
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Tuesday, March 13th, 2012 AT 11:36 PM
Tiny
SATURNTECH9
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Not sure if there is one there or not hook the test light to the postive battery cable. Then touch the case of the alternator see if the test light lights brightly. Your really going to need a multimeter so we can figure this out.
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Wednesday, March 14th, 2012 AT 12:18 AM
Tiny
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I have a multi meter and it says its holding about 12 to 13 volts after putting another ground on it.
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Wednesday, March 14th, 2012 AT 2:03 AM
Tiny
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So its charging at idle at that voltage?Also if you turn on the headlights blower fan on high etc whats the voltage?That car the voltage should be higher.
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Wednesday, March 14th, 2012 AT 2:20 AM
Tiny
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The volts will go around 10 when the lights are on
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Wednesday, March 14th, 2012 AT 2:37 AM
Tiny
RASMATAZ
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See charging system EWD below-start testing-For me sounds like the IVR @ 10volts lights On and engine running
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Wednesday, March 14th, 2012 AT 4:45 AM
Tiny
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What is that ivr you are talking about?
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Wednesday, March 14th, 2012 AT 2:56 PM
Tiny
SATURNTECH9
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He is talking about the internal voltage regulator. Lets see if we have power at the yellow wire with a white stripe and the two black wires with orange stripes at the alternator. Let me know what you find.
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Wednesday, March 14th, 2012 AT 5:02 PM
Tiny
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What would that be if I'm not getting power to them. I'm at work I get off at and will check when I get home.
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Wednesday, March 14th, 2012 AT 6:01 PM
Tiny
SATURNTECH9
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If you look at the wire diagram those wires are feed by fusable links so if there wasnt power you woud most likely have a fuseable link blown. Also did you have your old alternator tested out of the car?Did you have your new alternator tested before you left the store?
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Wednesday, March 14th, 2012 AT 6:07 PM
Tiny
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Now where would the fuses be inside the car where the fuse block is or in the line?
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Wednesday, March 14th, 2012 AT 9:35 PM
Tiny
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Look at the picture its at the starter relay
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Wednesday, March 14th, 2012 AT 9:38 PM
Tiny
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Okay thank you I'm going to check it as soon as I get off work.
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Wednesday, March 14th, 2012 AT 9:48 PM
Tiny
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There fused wires not fuses see if you have power first and we will go from there.
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Wednesday, March 14th, 2012 AT 10:03 PM
Tiny
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Okay I had to rewire the alternator case the replacement I got was a hard wire type plug. It goes from 2 black with orange stripes into 1 would it be possible if I got them mixed up wouldit not charge?
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Thursday, March 15th, 2012 AT 1:41 AM
Tiny
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It shows in the diagram two seperate feeds there both constant power feeds so if the two black with orange stripes were mixed up it should still charge Do you have three power feeds going into the alternator?Do all three wires have battery voltage going to them?
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Thursday, March 15th, 2012 AT 2:05 AM
Tiny
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I checked the volts going through the battery and it is 12.53 and I don't have anything but.008 on the casing of the alternator so it must not be getting anything. Idk where the fusible link is but I know where the starter selinoid is. I can't find any wire that goes to the alt. All I see is a yellow one that goes into the inside of the car.
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Thursday, March 15th, 2012 AT 2:56 AM

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