1970 Cpe Electrical Problem
Thread Starter
5th Gear
Joined: Aug 2004
Posts: 5
Likes: 0
From: New Hampshire
1970 Cpe Electrical Problem
Hi All!
I'm new to this forum so I'll try to be brief. My nephew owns a 1970 Vette Cpe w/350. The car will start and run w/o any problem. When it sits for about a week or less the battery has drained too far to start it. He applied a "Battery Tender" (charges at about a 1 amp rate, I believe) after disconnecting the battery ground cable. Tried it again about 3 days later---started fine. Shut it off; 3 days later, dead again. We checked the battery circuit by removing the ground cable and putting a test light between the negative battery post and the negative cable---light is 'ON'. Tried pulling all fuses---light still 'ON'. Started removing all the wiring that's non-fused, one circuit at a time--light still 'ON'. Is it possible that the battery is bad? He claims it's only 8 mos. old (Interstate). Or is it also possible that the negative cable is not making good enough ground at the rear cross member? We looked at it and it appears pretty cruddy! I'm no electrical expert but I've done lots of circuit tracing on British cars over the years---maybe I'm too old to think straight but this one has me ticked off now!! Any help would be greatly appreciated.
I'm new to this forum so I'll try to be brief. My nephew owns a 1970 Vette Cpe w/350. The car will start and run w/o any problem. When it sits for about a week or less the battery has drained too far to start it. He applied a "Battery Tender" (charges at about a 1 amp rate, I believe) after disconnecting the battery ground cable. Tried it again about 3 days later---started fine. Shut it off; 3 days later, dead again. We checked the battery circuit by removing the ground cable and putting a test light between the negative battery post and the negative cable---light is 'ON'. Tried pulling all fuses---light still 'ON'. Started removing all the wiring that's non-fused, one circuit at a time--light still 'ON'. Is it possible that the battery is bad? He claims it's only 8 mos. old (Interstate). Or is it also possible that the negative cable is not making good enough ground at the rear cross member? We looked at it and it appears pretty cruddy! I'm no electrical expert but I've done lots of circuit tracing on British cars over the years---maybe I'm too old to think straight but this one has me ticked off now!! Any help would be greatly appreciated.
Drifting
Joined: Aug 2002
Posts: 1,731
Likes: 22
From: Marietta Ga.
I seem to recall that can be caused by the alternator. I am trying to find a past thread.
Here's one, but not the one I remembered
http://forums.corvetteforum.com/show...t=dead+battery
Here it is
http://forums.corvetteforum.com/show...t=dead+battery
Here's one, but not the one I remembered
http://forums.corvetteforum.com/show...t=dead+battery
Here it is
http://forums.corvetteforum.com/show...t=dead+battery
Last edited by 72GACRZR; Aug 25, 2004 at 06:32 PM.
Burning Brakes
Joined: Jul 2004
Posts: 763
Likes: 42
From: Detroit MI
St. Jude Donor '05-'06-'07-'08-'09-'10
It seems that you have gone through all of the proper circuit tests. This was a problem on my '70 and I discovered that it was the center compartment door behind the seats. If it is not shut the whole way, the light inside will slowly drain the battery in around 3 days. Good luck.
Instructor
Joined: Jul 2004
Posts: 210
Likes: 0
From: Missouri
Well if you had the battery disconnected from any charging source and it was full charged when you let it set for 3 days I'd say you have a wore out or bad battery.
The alt if the diodes/reg/stator are blown out they will drain the battery just like leaving a dome light on. If you run a voltage test across the (full charged GOOD) battery it should charge about 13.8-14.2. If its above that its most likely the regulator causing the problem if its below 13.8 it still could be the reg, stator or diodes. If its just battery voltage say 12.5 and stays there no matter what it could be anything.
If your battery is getting old 3 1/2-4 yrs old make sure you invest into a new battery. A battery is the most important part of the electrical system.
The alt if the diodes/reg/stator are blown out they will drain the battery just like leaving a dome light on. If you run a voltage test across the (full charged GOOD) battery it should charge about 13.8-14.2. If its above that its most likely the regulator causing the problem if its below 13.8 it still could be the reg, stator or diodes. If its just battery voltage say 12.5 and stays there no matter what it could be anything.
If your battery is getting old 3 1/2-4 yrs old make sure you invest into a new battery. A battery is the most important part of the electrical system.
Burning Brakes
Joined: Oct 2001
Posts: 911
Likes: 5
From: TN
70 Electrical
Have a 70 myself with a old, old Interstate battery installed in Dec of 1996. Still cranking. Check the wiper override switch and see if it could be turned on. If it is on it will draw current all the time.
Thread Starter
5th Gear
Joined: Aug 2004
Posts: 5
Likes: 0
From: New Hampshire
Thanks guys for your responses.
As far as the alternator/regulator system, I believe we eliminated that when we disconnected ALL the hot circuits we could find. THe red lead on the alternator was disconnected while watching the connected test light and it still remained on. We've even disconnected ground leads from some of the charging/starting circuits as well. As for the battery, even though he purchased it new 8 months ago, there is the possibility that it developed a problem. He doesn't seem to have a problem getting it to take a charge, it's while sitting that it drains. I'm still waiting for him to have it checked out. When charged, it seems to hold a steady 12.5-12.8volts. While charging, it's steady at about 14.5 volts. Thanks for the heads up on the wiper over-ride switch and rear compartment door! I've asked my nephew to remove as much of the circuit wiring from the dashboard as possible to at least get it down to one certain area---would certainly make finding this short a lot easier. My suggestion to him was to remove the battery from his 1998 Chevy pick-up and try the same tests again. Until we can find a better wiring diagram, there's not much else I'd attempt to do at this point. Thanks again all!!
As far as the alternator/regulator system, I believe we eliminated that when we disconnected ALL the hot circuits we could find. THe red lead on the alternator was disconnected while watching the connected test light and it still remained on. We've even disconnected ground leads from some of the charging/starting circuits as well. As for the battery, even though he purchased it new 8 months ago, there is the possibility that it developed a problem. He doesn't seem to have a problem getting it to take a charge, it's while sitting that it drains. I'm still waiting for him to have it checked out. When charged, it seems to hold a steady 12.5-12.8volts. While charging, it's steady at about 14.5 volts. Thanks for the heads up on the wiper over-ride switch and rear compartment door! I've asked my nephew to remove as much of the circuit wiring from the dashboard as possible to at least get it down to one certain area---would certainly make finding this short a lot easier. My suggestion to him was to remove the battery from his 1998 Chevy pick-up and try the same tests again. Until we can find a better wiring diagram, there's not much else I'd attempt to do at this point. Thanks again all!!
Last edited by dizzyd; Aug 26, 2004 at 01:34 PM.
Drifting
Joined: Aug 2002
Posts: 1,731
Likes: 22
From: Marietta Ga.
Unless I am mis-reading your first post, the test light isn't going to tell you anything, because it will light by itself if it is the only thing between the positive and negitive post, as it completes a circuit.
Read the past threads about using a meter to check.
Read the past threads about using a meter to check.
Thread Starter
5th Gear
Joined: Aug 2004
Posts: 5
Likes: 0
From: New Hampshire
Originally Posted by 72GACRZR
Unless I am mis-reading your first post, the test light isn't going to tell you anything, because it will light by itself if it is the only thing between the positive and negitive post, as it completes a circuit.
Read the past threads about using a meter to check.
Read the past threads about using a meter to check.
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