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Topic: Battery Light & Interior Light On

in Forum: C3 Electrical


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Battery Light & Interior Light On (6/16)
 9/5/09 9:49am
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

Does sound like an alt problem. Ya might take it off an have Pep Boys(or some other place) check it out on a machine first. If you have the service manual, there is info in there on how to test the various components. Ken could tell you/us the procedure, but I'd have to look it up and post it.

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Joel Adams
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Battery Light & Interior Light On (7/16)
 9/6/09 6:09am
CeeDee
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, - New Zealand

Vette(s):
Silver '81 mostly original C3. Silver interior, bilstiens, big sway bars, headers.


Joined: 3/26/2005
Posts: 232

Just out of interest, what type of battery did you get for your new one ?

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Kiwi Chris

Battery Light & Interior Light On (8/16)
 9/7/09 1:38pm
DougK
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Destrehan, LA - USA

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Red/Red 1981 Previous owner includes New York Yankee Don Mattingly. NCRS Top Flight


Joined: 1/20/2003
Posts: 24

Sears Die Hard.  I am looking for an alternator out of a 1980 or 1981 that has a date code from 7/80 - 10/80 if anyone knows of a source.  Thanks.

Battery Light & Interior Light On (9/16)
 12/31/09 8:26pm
DougK
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Destrehan, LA - USA

Vette(s):
Red/Red 1981 Previous owner includes New York Yankee Don Mattingly. NCRS Top Flight


Joined: 1/20/2003
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Finally completed the repair.  It took awhile because I searched for an alternator with a date code a few months before my 10/80 build date.  Found the alternator but it was in bad shape; I had it rebuilt and restored.  Installed and it finally works great.
Battery Light & Interior Light On (10/16)
 12/31/09 11:47pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

Good to hear!! Thumbs Up

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Joel Adams
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

Battery Light & Interior Light On (11/16)
 1/1/10 2:45pm
kstyerLifetime Member
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CUYAHOGA FALLS, OH - USA

Vette(s):
1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!


Joined: 12/2/2003
Posts: 6424

If anyone wants to know how, I can repost the procedure for rebuilding/repairing the alternator.
Battery Light & Interior Light On (12/16)
 1/1/10 4:03pm
CeeDee
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, - New Zealand

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Silver '81 mostly original C3. Silver interior, bilstiens, big sway bars, headers.


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Yes please Ken !  Don't need it yet, but can never have too many "tools" at hand for when the day comes Wink

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Kiwi Chris

Battery Light & Interior Light On (13/16)
 1/3/10 11:42pm
kstyerLifetime Member
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CUYAHOGA FALLS, OH - USA

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1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!


Joined: 12/2/2003
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I went back in the history files and found the post. 
So here you go!
 
 
To inspect and replace the alternator diodes.

 

This applies to the 1974 and newer alternators with the internal regulator.

 

Once the alternator is off the car, place it with the pulley down.  You will see four bolts around the outer diameter of the case.  Remove the bolts.

Now the back half of the alternator case can be lifted off of the other sections.  You will see a thin center section between the alternator halves.  Make sure this part stays with the back half of the case (opposite side from the pulley).  As you lift, you will hear a light snap.  This is the alternator brushes dropping out of place.  Two springs may fall out.  These springs will look like a spring in a ball point pen.

 

Inside the back half you just removed you will see the brushes hanging by a ceramic holding fixture.  Looking at the outside, you will see a small hole that lines up with holes in the ceramic brush holder.  Place the springs back in the section where they were in the holder, and where the brushes slide in place.  Now line up the brushes and slide them back in place.  Insert a piece of wire, toothpick etc, into the hole from the outside of the housing, and into the hole in the brush holder.  Push the brushes backing far enough that your pin will hold the brushes back in place.  Insert the pin far enough to go through the top hole on the brush holder.  This the only way to hold the brushes back in place when reassembling the alternator later.  If the brushes are worn get a new set.   They will come installed in a new holder.

 

Now look down in the alternator back half.  You will see the center section is bunch of wires in a wound bunch.  This is the alternator stator.  You will see three wires from the stator held in place with three nuts.  Remove the nuts and lift the stator out of the case.  Use an ohm meter and make sure all three wires in the stator have contact with each other.  If not, replace the stator.

 

Where you removed the nuts you will see three taps going to a rectangle block with another tab going to the regulator and brush holder.  The same screws hold the regulator as the brush holder.  There are three of them.  Two of the three have insulators under the screw heads.  Don�t mix them up.   Remove the screw holding the last tab on the block and lift the block out of the alternator.  This block is the light minder diode, also known as the diode trio.

 

Use an ohm meter set to diode check.  Touch one lead to the single tab on the trio, and touch the other meter lead to each of the other three tabs, one at a time.  Read the meter.  Now reverse the leads and check all three again.  One combination of the leads will show an open circuit on all three of the other tabs.  When reversed you should read an almost equal reading at all three.  If it fails either way, replace the diode trio.

 

Now back down inside the case. And back to where you first removed the three nuts.  They are located in the rectifier bridge.  This contains six more diodes.  These affect the charging rate, and control changing the three phase A/C into D/C current.  Rotate the case so the rectifier bridge is at the top of the case.  This is just for reference and description.  With the case in this position, you will see cooling fins on both the bottom and top side of the bridge.  Connect your ohm meter lead to the bottom set of fins, and check the three lugs where the nuts were.  Now reverse the leads, just like you did with the trio, and take another set of readings.  Again, there should be an open circuit one direction, and a constant even reading with the leads reversed.   This checks three of the six diodes.

Now put one of the meter leads on the top set of fins, and repeat the checks to test the other three diodes.   If any of the diodes flow both ways, or are open both ways, you will need to replace the rectifier bridge.   It is held in place with a screw into the case on the right side, and by the nut holding the terminal on the battery connection on the outside of the case.  Remove those and the wire from the condenser and the bridge lifts out.  Be sure to reinstall the insulator on the battery terminal, or the electrical system will short out, and blow a fusible link by the starter.  If all test were good but the alternator does not charge, replace the voltage regulator.

 

Before reassembling the alternator, look at the two copper rings on the alternator rotor in the front half of the case.  If they are rough and burned gently sand them to a smoother surface.  Don't sand too much or you will need a new rotor.  You can't put the copper back.  It's best to hold the rotor upright, and wrap a piece of very fine sandpaper around it, and pull back and forth like Chubby Checker doing the twist.  This way you don't create low spots. Use your ohm meter again, and make sure there is a connection between the two copper rings.  If not, you will need a rotor.  This is fairly rare.

 

Be sure to remove the pin, toothpick, etc after assembling the alternator.  If you forget, the brushes won�t make contact and the alternator won�t charge.

  

Once the alternator is off the car I can do all of this in about 10 minutes.  It's not that tough. Your first time will take quite a bit longer.  Just take your time.

kstyer2010-01-03 20:43:46
Battery Light & Interior Light On (14/16)
 1/8/10 3:43pm
Autom8r
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Old Hickory, TN - USA

Vette(s):
1978 L-82 Silver Anniversary hotrod. /////////////


Joined: 5/26/2003
Posts: 599

darn Ken, first time I have seen the pic in red. Looks cool (and very wet).

I have a similar non-alternator related interior light problem. I had some work done on mine in spring '07 by a 'Vette savvy back yard mechanic, including some electrical work. A week after I got it back from him my battery died. Closer inspection revealed the interior lights were on with the doors closed.. It took over a week for the problem to show up. My immediate solution was to remove all the bulbs then forget about it, and it's been that way for over 2 years. I'd take it back to the guy but he is now a 75 mile drive away. Anyone have any ideas what to look for??

Happy New Year!!

Dave
Battery Light & Interior Light On (15/16)
 1/9/10 2:28am
tb2k82ceLifetime Member
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Lemon Grove, CA - USA

Vette(s):
1982 C3 Collectors Edition 44000 miles, sat in the sun most of its life, My wife purchased it for me for Father's Day in 2007 from her girlfriend that had it for 19 years. It is on the road again. I'm retired but it is now my daily driver.


Joined: 10/17/2007
Posts: 2041

Autom8r  Could you start this as a separate post.  I have the same problem and just undid the light as a quick fix.  Would be interested in answer's to this one.
Battery Light & Interior Light On (16/16)
 1/9/10 10:35am
Autom8r
Former Member

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Old Hickory, TN - USA

Vette(s):
1978 L-82 Silver Anniversary hotrod. /////////////


Joined: 5/26/2003
Posts: 599

Done (almost)...
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