RE: ELECTRICAL SYSTEM PROBLEMS WITH VOLTAGE

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I have a 97 Chevy Blazer 4x4 with a little over 113K miles. I've been having problems with the voltage for a while now. The voltage gauge swings from 14v to about 10.5v when I stop at a traffic light or a stop
sign. I'm convinced the gauge is not to blame because when I put a load on it, it indicates 10 to 10.5v, the Dash lights dim, the headlights will also dim. I've already replaced (3) alternators on this Truck (2) batteries within (4) months and everything is still the same. The gauge will read just above 14v and sometimes even 16.2v while am driving the truck with no problem but the minute I stop at a traffic light the Voltage Gauge drops down to 10v or 10.5v depending on what accessories am runnning on my truck. The truck starts up good and the Voltage reads a perfect 16.2v but the minute the truck is warmed up the Voltage then starts to drop to about 11.5v then to 10.5v and then to10v Depending on what accessories is running on the Truck. Temperature and frequency between trips seems to not make a difference either. The only thing I have done to the truck even remotely connected to the electrical system is to swap the radio, but I used a wire harness to connect the wiring. I've already checked for loose wires or bad grounds and their is none. I've even had a addtional grounding wires installed but that did not help either. Other than I'm lost. Any help?
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Maybe check the alternator
wrote:

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THANKS FOR YOUR REPLY BUT I ALREADY DID THAT. AND I 'VE EVEN REPLACE IT 3 TIMES AND I STILL HAVE THE SAME PROBLEMS..
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wrote:

I think it might help to quote the original msg. in your reply... so that others in the group could see the question and the reply and provide additional information if needed.
you can configure your newsreader to do this automatically.
--
Elbert Clarke
elbert.clarke@**adelphia.net
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I just went through this on my '95 Monte. Mine turned out to be bad connections at the power distribution block.
First thing I did was test to see if the low voltage was system wide. I did this by checking the voltage at every fuse and isolating which ones were at the low voltage. Only a few were at the lower voltage and others were normal. The voltage at the battery was also normal. This lead me back to the power distribution block beside the battery. I took it all apart, cleaned it up and all is like new.
Here's a link to the thread:
http://tinyurl.com/d2qnp
Steve

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WHAT YOU WROTE SOUNDS LIKE IT WILL FOR ME BUT I NEED YOU TO WRITE THE INSTRUCTIONS DOWN FOR ME STEP BY STEP AND WITH MORE SPECIFIC DETAILS IF YOU MAY ...PLEASE .. EMAIL ME THANKS IN ADVANCE!!
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Try checking the voltage right at the battery. With the engine at a fast idle and no accessories, then at a fast idle with headlamps on and the heater blower on high. If you need a meter, Harbor Freight has them for around $4.00 on sale. There are more tests to make but start with these. One seemingly obvious thing a lot of folks miss is the belt. It has to be tight.
Al
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I DID THAT ALREADY AND IT READ JUST FINE.. AND I STILL HAVE THE SAME PROBLEMS.. THANKS FOR TRYING TO HELP ME..
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Other than I'm lost. Any help?
Check your ground...from the battery to the frame.
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I ALSO DID THAT. I EVEN HAD ADDITION GROUNDS INSTALLED TOO. AND THAT DID NOT HELP..
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Bullet wrote:

    Before changing another battery or alternator: Clean the terminals. Check the pig tail from the distributor for damage or a lose wire in the connector. Get 'em warmed up, and take a trip to a autoparts store that has a battery & alternator in vehicle load tester. Have it checked. Have them run the test a few times try different accessiories. Charles
    
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I'LL CHECK THAT TO SEE IF IT'S A PROBLEM THANK YOU FOR YOUR REPLY!!!
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I had a similar problem on my 95 5.7 K1500 trailer towing package several weeks ago.....was getting low voltage and had a leaking battery terminal. Replaced the battery and the starter went out the next day, don't think it was related as I just replaced it 6 wks before (200,950 miles on the original starter!), just a bad rebuilt starter. Anyway, replaced the positive battery cable that goes from the battery to the drivers side firewall distribution box as it was corroded from the inside from where the battery had been leaking into it. The trailer towing package has two positive leads that go to the positive side of the battery. One goes to the starter and the other goes to the firewall distribution box. Cleaned all connections and still had the fluxuating voltage. Would crank right up first in the morning then later wouldn't crank at all, would just click. Would tighten up the battery terminal, and would work fine for a little while and start the whole process over. After overtighting the terminals on two batteries and causing the positive side side mounts to come out we found out what the problem was. The lead spacer that goes between the positive side cables to the positive side post of the battery had been squashed down to less than a 1/4 inch over the years. I put in a new spacer, it is like a half inch or more in thickness and now that has fixed all of my electrical problems. What was happening with the old spacer was that when I tightened down the terminal on the positive side the long battery bolt would go thru the side mount bung and poke a hole thru the battery. Thank goodness for O'Reilly's liberal battery return policy, as it took two batteries to discover what the problem was. Now both the terminals are good and tight and I get a solid 14 volts in the middle of the voltmeter all the time now. This is a little long winded but hopes it might help someone out there......Mark

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The lead spacer is a typical problem. It can also cause alternator failures.
Cheers

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This is normal. Believe it or not. The alternators are set not to deliver full power at idle so they will not fail in hot weather.
One way around this is to get a smaller alterantor pulley. Since you changed the alternator, you may have gotten a larger pulley by mistake. You can calculate the rpm needed, then using the diameters find a smaller pulley that will help. Dont go too small, as the alternator may then fail because it will be subject to higher rpms are higher engin speeds (4500 rpm). I believe 8000-9000 rpm is the upper limit.
Another approach is to replace the alternator with a larger unit, such as those used on police and fire vehicles. http://www.wagneralt.com /
And if your savy, you can experiment with different mfgs' voltage regulators, this worked for me.
Good luck

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fail in hot weather.
Erroneous statements.
An alternator outputting 10.5V at idle is NOT normal. At idle, an alternator will put out anywhere between 13.0V and 14.5V depending on load. If the battery is at a low charge, you can expect to see around 14.5V. If the battery does not require any charging and there is no big load (ie high beams, rear defogger, large stereo), expect to see 13.5V or so.
What is the source of your information?
Steve
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On Thu, 24 Nov 2005 00:29:38 GMT, "Steve Mackie"

as you say above the alternator has to put out over 12.v at idle to charge the battery. At idle once again you should see around 13.v if the alternator is working properly. I believe the amp output changes with rpm and load.
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You seem to have left out the fact that th OP stated that 'Under load' the voltage drops to 10-10.5 volts at idle.

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Yup, was I supposed to include that in my response?

voltage drops to 10-10.5 volts at idle.

not
alternator
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Although, this is GM's response to the problem:
http://users.eastlink.ca/~smackie/tsb001.pdf http://users.eastlink.ca/~smackie/tsb002.pdf http://users.eastlink.ca/~smackie/tsb003.pdf
But not mine. When my vehicle started to exhibit these symptoms I fixed it. My mom's Intrigue started doing it and the dealer wouldn't do anything other than respond with "it's normal." She didn't care anyways, got rid of the car.
Regardless, if it didn't do it when it rolled off the assembly line, it's not normal and it can be fixed.
Steve

the
will
the
high
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