1973 Battery Discharge
Thread Starter
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Joined: Nov 2016
Posts: 50
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1973 Battery Discharge
Hi,
My 73 will discharge the battery in 48 hours. Battery has been tested good. When running, alternator is putting 14 + VDC to the battery.
With car shut off, no lights are on, radio is off, etc. What I have found that seems wrong is that with everything off, I have battery voltage at the number 1 terminal of the alternator. I also have battery voltage at terminal 2, but I believe that is normal. When I measure battery voltage at terminal 1, that is at the plug, disconnected from the alternator.
Any suggestions where to look next?
Thanks,
B
My 73 will discharge the battery in 48 hours. Battery has been tested good. When running, alternator is putting 14 + VDC to the battery.
With car shut off, no lights are on, radio is off, etc. What I have found that seems wrong is that with everything off, I have battery voltage at the number 1 terminal of the alternator. I also have battery voltage at terminal 2, but I believe that is normal. When I measure battery voltage at terminal 1, that is at the plug, disconnected from the alternator.
Any suggestions where to look next?
Thanks,
B
Pro
Joined: May 2006
Posts: 595
Likes: 84
From: Colonial Beach Virginia
Had a similar situation. The PO had dropped the steering column for some reason. When he reinstalled it, it pinched the horn relay wire in the ribbon cable. That enabled the relay to be on full time. The horn itself was disconnected. This would drain my battery over about 48 hours as well.
Le Mans Master
Joined: Aug 2006
Posts: 7,427
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From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi and Welcome.
You should NOT have any voltage on field terminal #1 with the key OFF.
Terminal #2 has voltage with the key OFF.
73 Schematic:
https://docs.google.com/viewer?a=v&p...ZTM0ZDc1MWM5Ng
Terminal #2 has voltage with the key OFF.
73 Schematic:
https://docs.google.com/viewer?a=v&p...ZTM0ZDc1MWM5Ng
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi again.
Yes, the ignition switch may have failed or possibly just out of adjustment.
Is this a new problem or has it been a problem for a while?
Did this start after changing out the starter?
Pete.
Is this a new problem or has it been a problem for a while?
Did this start after changing out the starter?
Pete.
Thread Starter
Advanced
Joined: Nov 2016
Posts: 50
Likes: 7
Hi,
This is a new problem. No components such as starter, etc have been replaced in many years. I have owned the car for 14 years, the starter was replaced about 10 years ago and has and still works well. Steering column has not been tampered with either.
Guess I will try to get to the ignition switch this weekend.
Thanks,
B
This is a new problem. No components such as starter, etc have been replaced in many years. I have owned the car for 14 years, the starter was replaced about 10 years ago and has and still works well. Steering column has not been tampered with either.
Guess I will try to get to the ignition switch this weekend.
Thanks,
B
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Not an easy task!
Jim Shea has published some very helpful instructions if you need them:
http://jimshea.corvettefaq.com/?p=1009
http://jimshea.corvettefaq.com/?p=1009
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Team Owner
Joined: Jan 2006
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From: Crossville TN
Remove the negative battery cable and connect an Ammeter between the battery terminal and the cable (use the 10 amp portion of your ammeter and hook (-) side to the battery). If there is NO drain on the battery, there will be no reading when you make the ammeter connections. Otherwise, there is a current drain and you need to find and eliminate it.
Pull all fuses out of the fuse panel (mark them accordingly!). Connect ammeter as described above. One at a time, install the fuses...checking for a current drain after each one has been inserted. Leave fuse installed if no drain is noticed. Continue until current drain is found. Remove that fuse again and diagnose that entire circuit [with an ohmmeter] to find where/how power is flowing to ground. Remember that this fault can be in the wiring, the connectors or in the components (internal failure). The vast majority of such problems are wear-thru of wire insulation. Alternator, clock, radio and powered antenna are sources where internal ground faults show up.
Pull all fuses out of the fuse panel (mark them accordingly!). Connect ammeter as described above. One at a time, install the fuses...checking for a current drain after each one has been inserted. Leave fuse installed if no drain is noticed. Continue until current drain is found. Remove that fuse again and diagnose that entire circuit [with an ohmmeter] to find where/how power is flowing to ground. Remember that this fault can be in the wiring, the connectors or in the components (internal failure). The vast majority of such problems are wear-thru of wire insulation. Alternator, clock, radio and powered antenna are sources where internal ground faults show up.
Last edited by 7T1vette; Dec 1, 2016 at 09:49 AM.
Burning Brakes
Joined: Oct 2015
Posts: 781
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7t1vette..Has it right..except, respectfully..I'd suggest not to pull all fuses and mark them..Simply remove them ONE AT A TIME and watch the ammeter to see if that fuse removal eliminates the parasitic current draw.IF NOT, REINSERT that fuse back into it's proper fuseholder position and go to the next fuse..Much simpler than pulling them all initially and marking them.Jim
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Jim..
Most of the time, either strategy will work. But, if you remove ALL of the fuses and still show a current drain, you know that the problem is with the primary electrical system and that everything downstream is fine. Saves a lot of wasted time.
Most of the time, either strategy will work. But, if you remove ALL of the fuses and still show a current drain, you know that the problem is with the primary electrical system and that everything downstream is fine. Saves a lot of wasted time.
Last edited by 7T1vette; Dec 1, 2016 at 11:09 AM.