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Old 04-27-2007, 04:30 PM
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alternator gm

I have a 1982 fire bird that i stuck a 305 /700r4 into and left everything on the engine stock- distributor, coil, etc..is my alternator overcharging at high rpm's ??? At idle my gage reads 13. roughly and at 1200 rpm and over the gage reads 15 volts .Is there a large power drain somewhere or is the alternator done ...or is that normal for the voltage output to go up at higher rpm's

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Old 04-27-2007, 07:09 PM
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Doc here,

While 15 volts IS a tad high, This could be caused by a few things..

The Normal Charge "Window" is 13.95 to 14.4 Volts. Below and above that indicates a problem OR future problem.
  • 1 ) The First of which, Might be the regulator Diodes May be beginning to fail, and the saturation Cutoff point may be above 14.4 volts before it shuts off the regulator. This is easily solved with a rebuild kit..Costs about $15 Fazools and takes a few hours of your time.

  • 2 ) Another , is the Rectifier Diodes are failing or one or more is reverse Biased (leaking backward) And the net result is somewhat less than 14.4 volts DC, like 10 or 11 Volts DC and the rest is RAW AC, 3 or 4 VAC (which will do nothing for state of charge, or system Support BUT damage Electronics if allowed to progress)

The Panel Instrument is NOT as sophisticated as a multi meter OR DVOM, To it, Volts is Volts..don't care whether it's DC or AC volts..

So in fact if you do a volt check at the battery with a DVOM, Set for DCV, V X 20 or higher, you may only actually see 11 volts DC..Not enough to top off the battery, AND support the system. The rest is AC..not good for anything but Electronic Damage. A Rebuild Kit will cure this problem as well.
  • 3 ) ALSO, The panel meter May just be out of calibration, not linear in sweep, and reporting .6 volts high..

    You can verify this by just doing the voltage test I just described at the battery, With a DVOM, And be sure the load is off the system (nothing that consumes power like AC, Heater lights etc..) running At A WARM curb Idle (choke dead open,) about 3 to 5 minutes after start up (to allow the battery to top off the drain of starting..

    Compare the readings, The Battery should read 14.4, AND if the Panel meter reads differently, It may be out of calibration..IF both are high, it may be a regulator or remote sensing problem.
  • 4 ) OTHER problems can be, Poor bonding of the alternator Ground. Run a 10 gauge ground wire to the ground buss in the vehicle at or near the battery.
  • 5 ) It also could be, bad remote sensing..The Small red wire on the alternator plug may be located at a 12 volt source at the end of high drain item, causing the regulator to run longer than it needs to. Relocate this wire to the BIG RED wire on the Alternator..the output wire. This will Shorten up the On/OFF cycles of the regulator.

Be sure all your connections are TIGHT, well bonded (use star and lock washers, and burnish off all paint from connection/ground surfaces) and The wire is of proper gauge (10 ga on the output, and ground, 12 or 14 on the top plug wires)

IF you decide to rebuild the alternator, Post back , Let me know, I'll give you step by step instructions on how to do it..

Doc
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Old 04-29-2007, 01:30 AM
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dear doc

Thanks for the input i think I'll rebuild it and see where i stand at least I'll know from square one where the prob is coming from .....I Appreciate your offer SIR for the diagram and i thank u greatly for your advice not to mention your knowledge..
i am one of the apparently few who can still rebuild an (old)alternator(no disrespect intended sir) or should i just refer to u as doc instead of sir??? sense you have obviously been around the game longer than I. Your knolage is the base for the next generation don't forget!!!! even if it takes awhile fore them to listen they will still thank you later ...as Do I ....omega
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Old 04-29-2007, 03:12 AM
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Quote:
Originally Posted by omega69
or should i just refer to u as doc instead of sir???
Doc Here,

Doc is just fine..

Last time anybody called me Sir, I was FORCED to wear REALLY UGLY Green Cloths, Get really BAD Haircuts, and Guy's were always raising their right hand up in the air at me..and people were shooting at me...

That or I thought my FATHER had just walked into the room..

And Yup, Olde Doc is high mileage..been around rods the north side of 40 years..

Back when you could actually get a 5 window Deuce Coupe at the Wrecking yard, and any parts needed, For $50 Fazools, Chop and Channel it, Custom paint it, toss in a "built to the hilt" 327 4 speed, Olds rear end, .. All on a Chevron Pump Jockey's Salary..(which wouldn't Fill the tank by today's standards) and do it VERY quickly..( BTW, I just described my FIRST "Barely" street rod..) Back in the "Dark ages"..

Geeze, My FIRST Driver's license was etched in Papyrus, in hieroglyphics,..had a Picture that was painted on from animal fat dye..by a Scribe..(actually it WAS paper and Black and white photo..When was the LAST time anybody saw one of those?)...

Heck, My birth Certificate is An artifact, that can only be verified by radio~Carbon dating..

Last Birthday I had, required the Fire Department standing by, and a Burn permit for when we lit the candles..and a had to be done in a wind tunnel to so as to blow them all out after...You needed a fire suit to even get close to the cake..

Didn't mean to imply that you Couldn't rebuild an alternator..I approach All my answers as If (and a lot are) the person is new to the task..so as to get a better Idea of what's involved to them..Since I haven't a clue as to their Tools or skill levels..and it makes it easier for them for the most part, to ask questions back when they get stumped..or con~Fuzzed..

Passing the "Baton" is what it's all about..If Good Rodding is to survive from generation to generation..Personally I have been involved with projects with lots of younguns' on their first projects ..and it never ceases to amaze me how much they "Soak up" by just working with them.. it's works the same way for me..The Kids have a lot to offer also, and I learn from them..

In Fact, I'm in the middle of one now, with my 17 year old Nephew And his dad (My Bro..) his ( My Nephew's) Very First project..We Will be sticking a "Well Built" 383 in his truck over the summer..

Dad and Unc sat there and drank Beer & Sodas, gave advise during the build, helped him build a Great tool box, and guided him on part selection..Kept him clear of all the Building "Traps", He Did all the hands on work..Now there is no stopping him! Planning project 2 already..

Thanks For your Compliments..

Doc
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