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Alterernator light came on and will not go off

 
chetspangler
I love my Chevy Chevette!
Posts: 6
Joined: 03/11
Posted: 03/12/11 05:51 AM

I have 78 Vette that has new battery, alternator and just about everything else.  While driving the alternator light came on and power windows stopped working. I changed the alternator but problem remains anyone have a solution?  

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waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 03/12/11 07:34 AM

you probably burned a fusible link at the starter.. possibly elsewhere..

do you have a test light?????/

turn the key on without starting the motor...

1.  do you have power at the output terminal on the back of the alternator..

2.  do you have power at the large red wire into the side of the alternator..

3.  the small wire will probably also have power on it.. if you unplug the side connector with the key on.. does the alternator light go out????/ it should..


you will want to print this page.. the upper right corner almost out of site until you open it fully is the alternator wiring diagram... for the 78...  the upper left is the starter diagram...edit.. i am almost sure that wiring diagram is drawn wrong.. the alternator output and the sense wire to the side of the alternator are almost always on separate fusible links.. additional edit.... both diagrams show that this is this diagram is correct..  but you will really need the exact wiring diagram..



0900C15280083715


if you have lost power at  test one...  you will have to replace the fusible link and the alternator as it will have burned out...

if you have lost power at test 2...  you just have to fix the fusible link...

please.... use a digital volt meter to test charging systems for output voltage...  NEVER EVER pull a battery cable to see if the alternator is working.. that test will damage the alternator ...

fusible links come in different gauges...  to properly select the correct size..  you have to know what size wire you are protecting.. and select a fusible link 4 numbers smaller...    
if you have a 10 gauge wire.. you use a 14 gauge fusible link
if you have a 14 gauge wire .. you have to use a 18 gauge fusible link..



oh... here is where the fusible links are probably stashed... edit.. i just noticed that this image shows the fusible link and the battery cable connection to the starter after it is disconnected from the top post of the solenoid..

Chevyfusiblelinks

~~~~~~~~~~~~~~~~~~~~~~~~~~~

here is another image of the starter .. this shows where the wires are connected.. see how close the wires are to the exhaust..   the wires can burn right there...  causing the fusible links to burn out..

Starterwiring

~~~~~~~~~~~
please use care .. and proper tools....  its not an easy job..  as you are probably going to have to remove the starter......   the power wires to the starter run inside a tube... its also possible that the wires have shorted out inside the tube. so while you have the starter off.. you might want to examine them...   and.. with care.. everything will fit back together without needing to bend and cuss at anything..

post what you find...  i will be back on late this after noon..

you may still also have a short...  and that is what may have caused the fusible link to burn..  

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waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 03/12/11 07:45 AM

additional.... the wire on the back of the starter is the alternator output wire.. it goes directly to the top post on the starter and has a fusible link right at the starter...

the large red wire on the side of the alternator is the voltage sense wire.. so the voltage regulator knows how much amperage to put out...

the small wire on the side of the alternator is connected to the amp light and then to switched power....

when you turn the key on.. power is sent to the bulb.. and the terminal on the side of the voltage regulator has less voltage on it... so the electrons flow through and light up the bulb...


when the alternator starts charging..  the voltage comes up on the alternator terminal . if the system is working correctly.. the light bulb will have equal amount of power on both sides.. this stops the electron flow and the bulb goes dark...  

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waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 03/12/11 08:13 AM

log in.. next to where you log out at is the message link... i sent you a link to an 8 page diagram...


the power windows are powered from a terminal block .. usually a red 2x3" plastic covered device with  a bunch of wires running into it..

the window relay gets turned on with power from the ignition switch.. so the circuit that supplys that could also be effected...

so.. do you also have power on the terminal block..  where ever its stashed on that car...  

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chetspangler
I love my Chevy Chevette!
Posts: 6
Joined: 03/11
Posted: 03/27/11 10:19 AM

Thank you.  It turned out to be that fuse which I had never heard of before.  

Now I have a noise in wheel/s that sounds like a turkey gobbler during mating season any ideals?  

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waynep7122
I mow my lawn and find Chevys
Posts: 1114
Joined: 08/09
Posted: 03/27/11 11:38 AM

loose lug nuts... have you checked them lately???? use a torque wrench set to 70 FOOT pounds..   apply pressure to the wrench slowly.. does it click before it moves???  it should..

bad wheel bearings... this involves jacking up each corner of the car.. grabbing the top and bottom of each tire.. seeing if there is any motion in and out at the top and bottom... .

loose brake caliper...   once in a great while...  the calipers if not installed properly can come loose...  wobble around on one bolt..


how are your various Universal joints in the 3 drive shafts????  one drive shaft between the transmission and the rear end..    the other between the rear end and the rear wheels...    when the U joints go bad.. they will sometimes make a squeaking sound..   they will for sure make a hollow sounding clank when you shift from drive into reverse.. as the load changed direction..

run over a wild turkey???

could be a dozen other things also...     hard to describe over the net..  

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chetspangler
I love my Chevy Chevette!
Posts: 6
Joined: 03/11
Posted: 03/28/11 07:14 AM

It sounds like U joints.  Thank you.  

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