Topic: Early C4 battery discharge
in Forum: C4 Electrical
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Cohasset, MN - USA
Joined: 11/28/2009
Posts: 44
Vette(s): 1986 Coupe
Red, saddle leather interior
Cast iron heads
This subject may have come up on this forum earlier. It seems that if I do not drive my '86 for about 5 or 6 days the battery voltage will drop below 12 volts. When driven, the alternator brings the voltage up quite soon. I use a battery maintainer charger. My daily driver does not discharge the battery and I can leave it undriven for more than a week with no problem.
Did these early C4s have excessive battery usage while turned off? Does the ECM, clock or radio tend to draw more current than usual?
Did these early C4s have excessive battery usage while turned off? Does the ECM, clock or radio tend to draw more current than usual?
91 Black Convertible
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Nashua, NH - USA
Joined: 11/4/2013
Posts: 20
Vette(s): 1991 Black Convertible w/ red interior
Another thing that I wonder about is, if you leave the key in the ignition, does the circuitry that reads the resistor pellet, put a continuous drain on the battery, also.
Hot Rod Roy
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Mission Viejo, CA - USA
Joined: 3/18/2015
Posts: 74
Vette(s): Yellow '84 Coupe
I can leave my '84 for a month without driving it (very rare), and it starts on the first twist of the key! With everything shut off (including the under-hood lights), but all normal stuff connected, my battery current drain is 0.01 amps.
|UPDATED|5/11/2015 10:54:09 PM (AZT)|/UPDATED|
|UPDATED|5/11/2015 10:54:09 PM (AZT)|/UPDATED|
91 Black Convertible
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Nashua, NH - USA
Joined: 11/4/2013
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Vette(s): 1991 Black Convertible w/ red interior
Hot Rod Roy said:
I can leave my '84 for a month without driving it (very rare), and it starts on the first twist of the key! With everything shut off (including the under-hood lights), but all normal stuff connected, my battery current drain is 0.01 amps.
My question is: Do you leave the key in the ignition for that month long period?
I can leave my 88 for probably a month or so with out any problems. And in answer to your question, no I do not leave the key in it.
How old is your battery? Sometimes they just start to go bad on you.
You may also have a parasitic drain happening. Make sure all lights are turned off. Places to check would be the under hood lights. Sometimes the mercury switches will fail. Also check the rear view mirror. The map light can get turn on with out you noticing. Same as the door lights. (push the light in the door to turn them off / on. LOL. Had my car a year or more before I found that was how they work.) Also the console light can give problems. I have also heard the power seats are a good place to look. If nothing is found, you can do a parasitic drain test.
When you try to start, is it no crank? When I first got my car I had this happen to me a few times. Would not crank, leave it for five minutes and it would fire right up. Turned out to be the ignition switch was not reading the resistance in the pellet correctly. This was a recall item in 88. I simply by-passed the key resistor and have had no problems since. Of course the proper way would be to replace the ignition, but I am cheap........
Good luck with finding your problem.
Charge battery to full charge and then have it checked at Advance, Walmart Autozone. If the battery is good it could be you have the map light on, or door sensor switch could be on when door is shut and it drains the battery in a week. Key in ignition does not have a current.
91 Black Convertible
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Nashua, NH - USA
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Vette(s): 1991 Black Convertible w/ red interior
Auto Motive said:
Key in ignition does not have a current.
Can you explain to me how this key resistance measurement is done without creating a current draw? Inquiring minds want to know.
Hot Rod Roy
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Mission Viejo, CA - USA
Joined: 3/18/2015
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Vette(s): Yellow '84 Coupe
91 Black Convertible said:
Can you explain to me how this key resistance measurement is done without creating a current draw?
Auto Motive said:
Key in ignition does not have a current.
Can you explain to me how this key resistance measurement is done without creating a current draw?
The current draw for the key resistance measurement must be down in the microamps category. Yes, there's some current draw, but it won't have any affect on your battery in less than six months!
in Forum: C4 Electrical
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