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1966 Nova alternater red light will not go out on dash.

 
fiasco64
I love my Chevy Chevette!
Posts: 3
Joined: 03/13
Posted: 03/26/13 08:00 AM

I am rebuilding a 66 Nova SS. I am having trouble with alternater light on dash that will not go out when running. I put in new reg, battery is good 12.8. When running the mulit meter reads 14.3. Alternater has been bench tested putting out 70 amps. Other people say diodes in alternater. Could I have lost the ground when I took the speedo out to repair? Don't know what to do anymore can anyone help with this.  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 03/26/13 01:31 PM

i have a test... takes less than 5 minutes...  lets run it...  you should be able to print this page...

~~~~~~~~~~~

Voltagedroptesting

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

also curious... do you have an externally regulated alternator...  or the later internally regulated version???

can you also run a voltage drop test from the alternator output terminal.. to the battery positive...


post the results..


you might also want to take a long jumper cable..... hook from the positive battery  and string it around on the ground to just out side the drivers door..

do a voltage drop test between the end of the jumper cable and the fuse box...

even something like the cigar lighter center terminal..

you could have resistance in the connections between the battery positive.. the terminal block behind the battery.. the horn relay connectors...  the bulk head connector..  the ignition switch or its connector...  or even at the dash board connector... i don't know how the dash ALT/GEN light is in the dash board on that one..


let me describe how the charging light works...

from the #4 voltage regulator terminal... it goes thru the bulk head connector and to one side of the alt/gen bulb..

the other side of that bulb is hooked to IGN 1 on the ignition switch...

what...

yep..

key on... the ign 1 voltage is higher than  the #4 terminal.  so the light comes on...

start the engine.  when the voltage regulator turns on with this voltage from the light..  as the charging voltage comes up.. the voltage on the #4 pin equals the voltage from the IGN1  circuit and the bulb goes dark...

if there is resistance any where between the 2 side.... you will have a dim or glowing light..

run the 4 part test on the bottom of the chart above.. post the results by number..

1....

2...

3...

4...  

and the measurement from the positive terminal to the alternator output terminal..

i will look up a wiring diagram in a little while and see if i can pick out some colors...

you might also want to verify that you have the engine block grounded to the firewall...

and by the way.. where is the regulator on that car... first gen camaros had it on the core support mounted on rubber isolators.. that required the voltage regulator to have its OWN ground connection from the core support to the regulator mounting foot..  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 03/26/13 02:05 PM

after you do what i have posted above.. should take less than 10 minutes..


lets look at these wiring diagrams..

66 Nova Wiring Left

and

66 Nova Wiring Right


see the generator light wiring.. .a pink wire and a brown wire..

the pink wire goes up to the  junction point that feeds a bunch of other circuits but is feed off the ignition switch.

the brown wire goes to the bulk head connector. where it continues to the #4 terminal on the voltage regulator..

but on the inside of the bulk head connector.. the brown wire has a brown and white stripe wire that connects accessory position of the fuse block..  hmm.. power from either terminal... IGN 1 or ACC... thats strange.. i can see it in print.. but i don't know why they would do it that way...

do follow on the right hand page... the smaller wire from the positive battery terminal... it usually goes to a terminal stud behind the battery .. then as described... over to the horn relay... from the other side of the horn relay to the bulk head connector onward ... its easy to follow with the diagram...  

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waynep71222
I have an SS396 tatoo
Posts: 448
Joined: 03/12
Posted: 03/26/13 02:10 PM

run one more.. engine running headlights on voltage drop test...

between the alternator output post.. and the voltage regulator terminal 3... while its plugged in by probing from the wire side of the connector on the regulator...  

that circuit goes from the alternator output terminal to the horn relay to then to pin 3 on the regulator.. if there is more than 0.02 volts DC.. you have an issue..  

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fiasco64
I love my Chevy Chevette!
Posts: 3
Joined: 03/13
Posted: 03/28/13 01:46 PM

I did the tests 1# is 14.6  #2 is 0.00   #3 is 0.00 #4 is 0.00. I have a externally voltage reg which is on the core support. I forgot to tell you when I got the car the horn is still not working all the parts under the horn are gone. Do have a horn relay in it. Also he put 2 gages in water temp & oil gage so those lights (idit) in the dash are out. He put two lights in the gages but the ones that are in the dash idit lights are out. I not the best on wiring problems. If it helps I can call you?  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 03/28/13 07:22 PM

test 1... 14.6
test 2...  0.00
test 3... 0.00
test 4... 0.00..  

2 3 and 4 and not what i expected... did you have the headlights on.. but...

take more measurements...

from the positive battery with the engine running and the headlights on...

positive battery post to the red wires on the horn relay...  



you should have only a small fraction of a volt..  0.04 or so...  you may have to turn your meter setting to 2 volts DC to read it..

now .. as i described above...  break out the jumper cables..  hook only the positive side up at the battery... place them under the car by the drivers door.. measure again... from the end of the battery cable to several fuses in the fuse block...

some of the fuses will have power all the time.. others are switched power...  which is the reason to test them all..  some are hooked to the power side of the ignition switch.. others are hooked to the IGN 1 or ACC side of the ignition switch.. i will have to look at the wiring diagrams above to see which ones are which...

if there is a difference in voltage inside the car.. and at the battery.. you will have a charging system light coming on...


say..i looked at the wiring diagram above.. i actually pasted both together and colorized the wiring beween the battery and the horn relay and the ignition switch..

can you measure the voltage at the cigar lighter...  with the engine running and the headlights on..

see how much you are getting...

at 14.6... i think you have an issue between the horn relay and pin 3... as you should have 14.1 or so..  or the case of the alternator is NOT properly grounded...  

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fiasco64
I love my Chevy Chevette!
Posts: 3
Joined: 03/13
Posted: 04/01/13 01:56 PM

I am sorry I did not get back to you till now. I did not have time to run your test yet. But I did put a new alternator on to make sure the diodes are working. I ran the 1st test over and I am getting 12.8,0.1,0.00,0.01. I will try to run other test ASAP. Thanks Mike  

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pepsi1
I mow my lawn and find Chevys
Posts: 1718
Joined: 09/11
Posted: 04/01/13 04:07 PM

I remember when the external voltage regulators aren't polorized correctly they can cause all types of problems....Just my 2 cents.

Bob  

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waynep712222
I have an SS396 tatoo
Posts: 251
Joined: 03/13
Posted: 04/02/13 06:19 AM

12.8,  is just barely charging at all...  

neg post to engine block.
0.1,   is too high...  clean the battery negative cable to engine block connections and at the battery terminal..

neg post to body.
0.00,    were the headlights ON???


engine block to body.
0.01.

add some additional tests..

alternator case... to the mounting legs of the voltage regulator... less than 0.04..

battery positive to the #3 terminal on the voltage regulator....


battery positive to the output terminal on the alternator...

output terminal on the alternator ... to the case of the alternator..  should be 14.1 to 14.6 volts.. probably closer to the 14.1...

please.. also... use your thumb.. with the engine off..  on the alternator fan blade... you should NOT be able to spin the alternator without turning the rest of the engine via the belts..  

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