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robdover
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Jul 17, 2009, 1:15 AM
Post #1 of 22
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Charging System Mystery
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I have a 1996 Chevy 1/2 ton Pickup with a 4.3 V6. after a couple of hard starts, I had to get a jump start the other day. Ive been reading 12.5V on the voltmeter with the engine running for quite some time now; replacing the serpentine drive belt didnt make a difference. I read 12V on the battery with my multi-meter with the engine off, and 12.5 V with the engine on. I pulled the battery and the alternator, took both to Advance auto parts for testing, and they shoed 14V 150A when bench testing my alternator. My batter tested 12V but only half the CCA required. They charged the batery for me for free, but when I reinstalled the alternator and battery, Im geting the same results, 12V on the battery with the engine off and 12.5V with the engine on; wunning the AC here in Hotlanta drops my voltage down to 11.5, thus draining the battery, and it is already somewhat hard to start. Any Ideas of where to look next?
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Hammer Time
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Jul 17, 2009, 2:18 AM
Post #2 of 22
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Re: Charging System Mystery
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Test for power at the main terminal of the alternator with the key OFF. If you have no power there, then your fusible link is burned out
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robdover
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Jul 17, 2009, 6:32 AM
Post #3 of 22
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Re: Charging System Mystery
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Thanks, but no luck there; any other Ideas?
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Hammer Time
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Jul 17, 2009, 7:50 AM
Post #4 of 22
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Re: Charging System Mystery
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What do you mean "no luck"? What did you find?
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jul 17, 2009, 7:58 AM)
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robdover
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Jul 17, 2009, 9:09 AM
Post #5 of 22
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Re: Charging System Mystery
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The fusible link is good, Im stil just getting 11.5-12.5V off the alternator, even though I had it bench tested and put out 14V 150A on the bench
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robdover
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Jul 17, 2009, 9:10 AM
Post #6 of 22
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Re: Charging System Mystery
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I might have better luck convincing my wife to let me buy that 78 Vette
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Hammer Time
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Jul 17, 2009, 9:31 AM
Post #7 of 22
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Re: Charging System Mystery
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What is the voltage at the main terminal of the alternator with the key off?
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robdover
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Jul 18, 2009, 1:52 AM
Post #8 of 22
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Re: Charging System Mystery
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12.5V at the main terminal of the alternator with the key off. The extra 1/2 V from what I said in previous posts is from the new battery my wife and father in law said would solve everything. I dropped $80 to prove them wrong.
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Hammer Time
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Jul 18, 2009, 2:36 AM
Post #9 of 22
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Re: Charging System Mystery
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Check for power at the brown wire of the alternator plug with the key ON.
If you don't find power, check the "gauges" #4 fuse at the instrument panel fuse box.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Jul 18, 2009, 2:39 AM)
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robdover
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Jul 18, 2009, 12:28 PM
Post #10 of 22
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Re: Charging System Mystery
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The little brown wire's continuity checks good- 12V at the terminal (ON). no fuses are blown in the instrument panel or in the fuse-relay center under the hood.
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Hammer Time
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Jul 18, 2009, 12:56 PM
Post #11 of 22
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Re: Charging System Mystery
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Well, that eliminates everything but the alternator. All I can say is something had to have been tested incorrectly.
Here is the wiring diagram
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robdover
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Jul 19, 2009, 2:39 AM
Post #12 of 22
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Re: Charging System Mystery
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AS afraid of that as I was, I am equally relieved. That was my original suspect, but when it bench tested good, and the battery checked ok, I was told by family that they have had a Battery Bench tested and it checked good when it wasn't. Thanks for your hel and the diagram.
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Sidom
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Jul 19, 2009, 4:41 AM
Post #13 of 22
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Re: Charging System Mystery
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The only other suggestion I would have is, if you have access to a different battery, swap them & rerun your tests....
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robdover
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Jul 19, 2009, 10:45 AM
Post #14 of 22
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Re: Charging System Mystery
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Thanks, guess I'll try that. A new battery and alternator have yet to yield any results. I've got an 02 Chevy Trailblazer that has a good battery I can use.
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robdover
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Jul 21, 2009, 10:02 AM
Post #16 of 22
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Re: Charging System Mystery
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Thanks for the tip; I crawled underneath, where I had been before to check the Black wire on the solenoid (from the battery) and for voltage there, and found that the other wire (purple) was still tight on its post, but the post had broken loose. They use a piece of black plastic on the front of the solenoid to hold the terminals in place. I pulled the starter, removed the soleniod and headed back out to the auto parts store where they sold me a replacement that ended up not being the same size- much larger for $50. I ended up dropping another $35 to get a new starter and solenoid, just like the one I put on 3 1/2 years ago. Its still starting, but a new starter, new battery, new alternator, new belt, having checked the system with a known good battery, and having checked all wiring in the charging system for continuity havent gotten me anywhere. I still read 12V on the battery with the engine on or off. Any other ideas?
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Sidom
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Jul 21, 2009, 4:58 PM
Post #17 of 22
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Re: Charging System Mystery
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That is strange..... This is a pretty basic system. There is not a whole lot to it. The few problems like you are experiencing I've ran across was loose connections at the starter. Like HT said either something was tested wrong or there is excess resistance in one of the few circuits (either power or ground) that's all there could be. If you are familar with doing a voltage drop test I would start there...... maybe throw a temporary ground on the alternator case (body & engine) for good measure.
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Hammer Time
Ultimate Carjunky
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Jul 21, 2009, 8:59 PM
Post #18 of 22
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Re: Charging System Mystery
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I'd also try running a jumper wire from the output pole of the alternator to the + side of the battery to double check the fusible link.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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rodjen700
Novice
Jul 22, 2009, 2:13 AM
Post #19 of 22
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Re: Charging System Mystery
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Hello,
I am amateur-electician, but I can say that if your batery is good as look to me, your VOLTAGE REGULATOR is dead as duck. Maybe 1 cell in car batery is dead-shortcut, but examine is it bubbling-making air in all cells. If one make no gas/air/bubbles yuor batery is passed away.
n.b. All measuring on car is more reliable vith analog instruments/ personal experience/ exept detachable resistors.
Best regards and Best vishes to succes.
M.P.
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Hammer Time
Ultimate Carjunky
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Jul 22, 2009, 2:23 AM
Post #20 of 22
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Re: Charging System Mystery
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Hello,
I am amateur-electician, but I can say that if your batery is good as look to me, your VOLTAGE REGULATOR is dead as duck. Maybe 1 cell in car batery is dead-shortcut, but examine is it bubbling-making air in all cells. If one make no gas/air/bubbles yuor batery is passed away.
n.b. All measuring on car is more reliable vith analog instruments/ personal experience/ exept detachable resistors.
Best regards and Best vishes to succes.
M.P.
First off, if read the whole thread before answering, you would know that the battery has already been changed. 2nd, the voltage regulator is part of the alternator and has already been changed at least once also.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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robdover
User
Jul 22, 2009, 4:21 AM
Post #21 of 22
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Re: Charging System Mystery
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My Radio Shack Digital Multi-meter suits me fine. Mystery solved. I think I had a bad alternator in the beginning, and a almost shot battery as a result. I tried a jumper for the fusible link, and didnt get any results there, but made another with some aligator clips and found that although the wire itself has no problems, the side terminal on the alternator (brown wire) was not making good contact in the plastic plug. Thanks for all your help; think I need to give credit to hammer time for pointing me in the right direction earlier.
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Hammer Time
Ultimate Carjunky
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Jul 22, 2009, 4:49 AM
Post #22 of 22
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Re: Charging System Mystery
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Glad to hear you got it solved. Thanks for posting the fix.
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