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two questions


Roeboat109's Avatar
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08-17-03, 10:03 AM   #1  
two questions

What is the best indicator that the alternator is not charging properly?my son had his truck jumped started and replaced the battery with a new one.then about a week later he called me after midnight from about 30 miles away.his truck wouldnt start.he had it jumped again ,but it olny ran a few seconds. I cleaned the battery post 94 gmc[one of gm better ideas] got it started and drove home.alternator reads about 11 or so consistently.turn off the engine ,turn on lights,start engine,lights dont dim at all. Ive always been told that is a good indication for alternator check for charging . what else do you recommend?his friends tell him its the alternator .im not so sure. just trying to help save my son some money.
my other son has a 96 t-bird that continues to burn fuses in instrument panel. he puts one in and it works for a little while then it blows again.doesnt seem to be any more serious than that but pain in you know what and who knows what its actually doing.? thanks very much. have a good day.

 
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power453's Avatar
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08-17-03, 10:31 AM   #2  
My family has an 84 chevy halfton my mother drives a 91 chevy suburban. They have both always had problems with the elctrical charging systems. What we have found is that with the engine running and at optimal effienciy the alternator should put out around 14.1 or so volts. Also if your alternator is putting out correctly when you turn on a heavy amperage device ( ie airconditiner) you will notice that the voltage will drop down for a split second and then the alternator will kick back in and bring the voltage back up. When you measure the battery when the vehicle is off it should read at least 12.6. Also check the voltage coming off the alternator itself. That would eliminate a bad wire from the alternator to the battery. As for the other question. It is mostlikly a classic short. Probably an interment type. The only way to fix that one is to get an electrical schematic and start checking the affected system.

 
power453's Avatar
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08-17-03, 10:35 AM   #3  
I thought of something else. My dad has always said that if your alternator is putting out correctly you can run your engine without a battery. We have done this and it proves to be true. What you do is start the vehicle, turn off all accessories and disconnect the negative battery cable. That will take the battery out of the system and the alternator will run it for you. IF you have an inductive style dc ampmeter available you could check how many amps the alternator is putting out. and of course check the voltage. If the the vehicle dies then the alternator is bad.

 
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08-17-03, 10:51 AM   #4  
Don't disconnect the battery cables on newer vehicles while the engine is running,you could wipe out some expensive components, get a inexpensive volt meter and check the voltage while running.
You can get a volt meter at most any store these days, Wallyworld etc. The volts should check 14.5V.
Use the DC scale on the volt meter.

 
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08-17-03, 11:30 AM   #5  
To add to what Comtnman said, place the positive(red) lead of the voltage meter to the big lug on the back of the alternator and place the negative (black) lead to a good ground, the battery negative side will work fine, but I prefer to ground to the body. With a good Alternator on THAT vehicle you should get at least 14.2 volts. A couple of things I have seen on these vehicle is that the fusible link (wire) will deteriorate and you will not get the proper charge to your battery. Also take the positive cable off of the battery and disassemble it. Clean all of the nasty corrosion from between the pieces. This will cause problems as well. Once you do this put it back together and coat it with a good battery cable protection chemical. I use a spray from Winzer, it works great. It even melts the corrosion away, but I dont suggest you rely on that solely.
Hope this helps ya,
Billy

 
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08-17-03, 01:05 PM   #6  
Joe_F
Removing the battery cable while the engine is running is a sure fire way to wipe out the diodes in the alternator as well as other stuff as mentioned. Plus, it proves NOTHING.

As mentioned, that's what a DVOM is for.

Sounds like a wasted alternator on the truck. Do a charging system test as I have it in my "The Basics" and report back with what that nets you. The dash gauge is useless for this test---you need a DVOM to be accurate.

As for the T-bird, need more description of the problem and which fuses are blowing.

 
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08-19-03, 05:54 AM   #7  
If you disconnct the battery on a running '94 burb, there is an excellent chance that you will ruin the alternator. Also, it's not real good for the ECM.
With the engine running, take a volt meter set it on DC at lowest range above 12 volts. Touch black lead to the battery neg or a known good dround. Touch the red lead to the heavy wire connector on the back of the alternator. This has a red plastic cap from the factory, cap just snaps off (if it's still there). If you're not getting 13.5 volts, the alternator is bad.
If you can afford it, spend the extra money on a good one or you'll be doing this about every 12-18 months.

As far as the T-bird... somethings going to ground. Isolate the loads from the fuse one at a time until the fuse quits blowing. You've got the problem isolated, disconnect the componet from the wiring, if fuse blows look for cuts worn wiring etc... if fuse doesn't blow, probably a problem with the component.

Let us know what you find!

 
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