1985 Chevrolet Silverado charging

Tiny
BUBBAKEG
  • MEMBER
  • 1985 CHEVROLET SILVERADO
  • 7.4L
  • V8
  • 2WD
  • AUTOMATIC
  • 74,000 MILES
Hello im having a charging problem with my truck the alternator is putting out 12 volts and so is the battery I replaced the alternator 3 times and its still not charging right I replaced the battery and same thing if I take off the pos battery when its running it shows the alternator is then putting out 15 volts but as soon as I hook it back up it then shows only 8 volts and if I turn the head lights on it drops as low as 6 volts the alternator I bought is a cheap one and says its suppose to put out 63 amps im thinking the the original alternator that was on the truck was bigger and putting out more amps I guess my question is is it possibe that this alternator just aint big enough thank you
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Saturday, September 13th, 2014 AT 2:16 PM

10 Replies

Tiny
HMAC300
  • EXPERT
Check items in pic these are on the starter and I'd bet on eof them is burnt up and not sending power they should have the same on like 12volts on both sides. They are available at auto parts. If you look on alternator it will be stamped or etched as to how many amps it has on the case by where you bolt it in.
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Saturday, September 13th, 2014 AT 3:30 PM
Tiny
BUBBAKEG
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Thank you the alternator that is on it now the new one is a 63 amp and according to Chevrolet dealer it came out with a 78 amp alternator so there is a 15 amp diff but would that 15 amp difference be enough to cause this thank again
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Saturday, September 13th, 2014 AT 4:54 PM
Tiny
BUBBAKEG
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Also I took the positive cable off the battery and I used one of those meter things lol and it was showing 12 amps coming up to the battery cable
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Saturday, September 13th, 2014 AT 5:01 PM
Tiny
HMAC300
  • EXPERT
The 15 amp difference isn't goin g to make a big difference unless you have a lot of power items like seats rear defogger etc and or maybe pulling a trailer. Just check what I said becais e those fusible links won't send power to alternator to make it work if they are burnt and I thin they may be.
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Sunday, September 14th, 2014 AT 8:10 AM
Tiny
BUBBAKEG
  • MEMBER
I checked all the fusible links they all look good I checked all fuses there good the other day I turned on the headlight and the radio went off I turned the lights off and it came back on that's a new one lol. Also the other day when we was checking everything with the volt meter we was starting the engine checking things and of course turning it off to check stuff again and had no problems starting it up. So I started home which is about 4 miles I stopped for gas and it wouldn't start like the battery was dead so I got a jump and it fired right up got home and shut it off and nothing acted like the battery was dead again so the next morning I went to put a charge on the battery thinking it was dead when I hooked it up it was 100% charged so I went to start it and it fired right up lol
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Monday, September 15th, 2014 AT 5:55 PM
Tiny
HMAC300
  • EXPERT
Ant LOOK at a fusible link you have to use either a test light or volt meter to see if power is going through it. Should be same voltage on both sides I'd bet this is your problem cause it's not charging.
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Tuesday, September 16th, 2014 AT 5:58 AM
Tiny
BUBBAKEG
  • MEMBER
Ok this is strange it started missing so I put a new cap and rotor on it with new spark plug wires runs great and its charging again what does a tune up have to do with the charging system I drove it and it went straight up to 14 volts even with the head lights on stays at 14 volts where it should be lol
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Wednesday, October 1st, 2014 AT 11:43 AM
Tiny
HMAC300
  • EXPERT
Hard telling it cold be a wiring issue because of age.
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Wednesday, October 1st, 2014 AT 12:03 PM
Tiny
BUBBAKEG
  • MEMBER
I unplugged the alternator and tested the 2 terminals on the alternator there is a number 1 and 2. Number 1 which the red wire goes two im getting nothing and the number 2. Brown wire goes to its shows 0.01 if I bring up the rpm it goes as high as 0.50 so I plugged it back in you can hear the alternator kicking is so I tested them plugged in and the red wire #2 its showing 12.3 volts. The brown wire #1 12.8 volts now with that unplugged should I be getting something from both those terminals on the alternator itself
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Friday, October 3rd, 2014 AT 5:43 PM
Tiny
HMAC300
  • EXPERT
The brown wire does have power and it shuts the light out. I still think there is afusible link problem. There may be two that run off of the starter but onemore in the harness running down the intake to the alternator. If you can't find it have a pro look at it. And make sure your battery is in good shape even if it is new, doesnt' mean it's good. Autoparts can test it. But I really think you have short in system causing your problem due to age. Either that or your fusible links are hanging on by one or two strands and don't let the power go through them like it shold and causes this.
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Saturday, October 4th, 2014 AT 5:38 AM

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