Question about 1988 GMC K2500

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Low voltage I replaced the alternator and battery and still voltage running at 11 volts turn lights on drops to 10 and even 9.8 volts

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Youre alt is internaly regulated so with it being new and youre battery is new follow youre wiers from youre alt to youre firewall making sure you dont have any bare wiers cuasing the system to have a week short and make sure all of youre conections from youre battery to youre starter and the alternator are cleane!

Posted on Jan 12, 2013


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Posted on Jan 02, 2017

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SOURCE: Battery light still on after changing alternator and battery.

i have a 2003 chevy silverado the riverse has not worked for 10.000 miles any sugesstionswhat this might be and or how much.

Posted on Jul 15, 2009

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SOURCE: battery test proper voltage, new alternator test

Battery by itself with no cable attach should read 12.4V for low and 13.6V for fully charged.

With both terminal connected a health charging system should read 13.6 to 13.8V

Amp gauge should read positive when chagring and when discharging it should be on the left (negitive side)


Key has to be out of the ign.

Charge battery to the max with terminals off the car.

Test voltage and make sure it's between 12.8 to 13.6V

Check the battery CCA and compare it with a battery load tester.
CCA that read 60% below the sticker is a BAD battery.

Cannect the + terminal.

Carefully touch the negitive terminal to the neg. battery post.

Make sure all doors and light are off

You should get a little spark.

A large spare is equal to a large load.

An amp meter will give you a better idea what the drain is.

A short is hard to find and it will take time.

Work on one fuse at a time until you find the load.

Posted on Jul 17, 2009

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SOURCE: 1996 GMC Suburban 5.7L cranks fast but doesnt

Using a volt meter, check the voltage at the battery terminals. If below 12v, disconnect the cables and check again right at the terminal contacts. If you have substantially better reading there, clean the terminal surfaces on the cables and the battery. If voltage is still below normal, fully charge the battery and have it load tested. Make sure that all ground points are in good clean condition as well. Without a good ground many relays and other components will not work correctly.
You cannot accurately do any electrical testing without a good fully charged battery installed.
Once battery is verified as good, check power at the fuel pump relay and at the pump. Also check for spark to isolate the problem further as being either the fuel or ignition system.
One thing though...If the engine seems to turn faster than normal, check that the distributor is turning normally while cranking. Fast turning can often be a sign of a failed timing chain. If so, compression will be very low as well. To do simple testing, either haynes or chiltons manuals are fine...Going deeper will require a better schematic and lots of patience. Doing any repairs without testing can get expensive very fast and no shop will do the work without tests because of that...You shouldn't either.
Once you find the primary problem, your other symptoms may disappear. They may or may not be related to the starting problem but that should become more clear as you do tests.

Posted on Jan 21, 2010

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SOURCE: Can an alternator drain the car battery in a few

Yes, the internal voltage regulator can stick and drain your battery in no time at all.

Posted on Apr 22, 2010

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SOURCE: alternator not charging


Posted on May 30, 2010

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Sounds like a bad alternator. Drained your battery and when you turned on the lights it took all the power left in your battery. When you drain a battery down that far, they are real hard to jump, and coupled with the alternator, the car is not producing enough current to start and stay running.

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Have your alternator checked, the voltage regulator which is an internal part in your alternator may be going bad and when there is an electrical load. The alternator does not produce enough voltage. That a multi meter and check your voltage at the battery, engine not running you should have 11.5 to 12 volts.
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what is the condition of the battery cables you are probably onto something about a ground but i dont think your ground issue is going to be at the batteries you may not have a good ground on the alternator. The next thing I would check is ... the alternator itself do you know that you are getting between 13.6 and 14.2 volts out of the alternator, a under charge or a overcharge condition both are bad for batteries.

I would check alternator output first if it is not within the above range you need to replace it

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