85 battery drain issue
Thread Starter
Cruising
Joined: Apr 2006
Posts: 12
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85 battery drain issue
hello i have a 85 c4 that webt from draining the battery from several days to overnite.here is what i have done so far put a volt meter in line and draws 12.55 i pulled all the fuses and relays but the draw is still there.unplugged the ecm,alt,antenna,headlight motors and 3 relays under the hood.any ideas?
Team Owner
Joined: Aug 2004
Posts: 22,303
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From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
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hello i have a 85 c4 that webt from draining the battery from several days to overnite.here is what i have done so far put a volt meter in line and draws 12.55 i pulled all the fuses and relays but the draw is still there.unplugged the ecm,alt,antenna,headlight motors and 3 relays under the hood.any ideas?
Could be your factory alarm system.
Team Owner
Joined: Mar 2001
Posts: 54,124
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From: Cincinnati, Oh USA
To measure current, you use an ammeter, or a milliammeter and connect it in series with a disconnected battery cable, preferably the negative battery terminal. You do not use a voltmeter!!!!!!!!!!
GM says leakage current shouldn't exceed 50 milliamps. My 87 draws 27 ma. Watch the ammeter while your pull each fuse and the one that makes a dramatic drop in current is the circuit that you need to inspect.
Also, behind your battery is the jump start terminal that has 8 red wires on it that use a fusible link, and these wires should be disconnected one at time while watching the ammeter if you don't find any leakage by pulling fuses.
GM says leakage current shouldn't exceed 50 milliamps. My 87 draws 27 ma. Watch the ammeter while your pull each fuse and the one that makes a dramatic drop in current is the circuit that you need to inspect.
Also, behind your battery is the jump start terminal that has 8 red wires on it that use a fusible link, and these wires should be disconnected one at time while watching the ammeter if you don't find any leakage by pulling fuses.
Thread Starter
Cruising
Joined: Apr 2006
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its all coming back to me know shop class was 20 years ago on the 20m scale it cycles 42.8 31.9 23.0 15.6 and drops i asume as it takes power from the battery. also i noticed mt security light doesnt flash any more. also i have no door or under dash lights but have hatch lights only when hatch is open. when i started today the battery was unhooked and it read .006 i hooked it up started the car then shut the car off and did t dest again and thats when i noticed it cycling. any ideas what to test next?
Team Owner
Joined: Aug 2004
Posts: 22,303
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From: Sussex,Wi
2023 Corvette of the Year Finalist - Unmodified
2022 C3 of the Year Winner - Unmodified
The horn/security system fuse is right behind the DIC. The relay is probably also
for the horn/security system. If it's warm, the coil is probably going bad, or the alarm is constantly running, but the horn ain't beeping because the fuse may be blown (15 amp)
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Make sure you don't leave your key in the ignition when you park your C4 because that keeps the theft detterent circuit on and will discharge your battery.
With the battery disconnected, your milliammeter should read zero! Also, your information is inadequite for us to provide any help. If your milliammeter is set to 20m (I am assuming 20 milliamps full scale), then you won't see any reading over 20, so why do you even have any meter readings exceeding 20? You need to better explain your meter connections and conditions.
With the battery disconnected, your milliammeter should read zero! Also, your information is inadequite for us to provide any help. If your milliammeter is set to 20m (I am assuming 20 milliamps full scale), then you won't see any reading over 20, so why do you even have any meter readings exceeding 20? You need to better explain your meter connections and conditions.
Last edited by jfb; Aug 14, 2007 at 12:50 AM.
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Thread Starter
Cruising
Joined: Apr 2006
Posts: 12
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the key is out it reads 0 after i hook up the battery but after i start the car is when it cycles the numbers i listed. the way im testing is pulling the postive battery cable and probing between the wire and the battery. what should my mulitmeter be set on?i am rust with my electrial repair skills
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
the key is out it reads 0 after i hook up the battery but after i start the car is when it cycles the numbers i listed. the way im testing is pulling the postive battery cable and probing between the wire and the battery. what should my mulitmeter be set on?i am rust with my electrial repair skills
Instructor
Joined: Jan 2006
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Something to think about...
Consider buying a schematic of the wiring harness (maybe they're on the net somewhere for free).
This will give you a bird's-eye-view of the entire sustem. It will allow you to isolate systematically.
And would be a much more efficient use of your time and efforts in your endeavor.
Your job once you get the schematic is to prove what it is not. A little at a time narrow it down and then voila.
Just one man's opinion.
This will give you a bird's-eye-view of the entire sustem. It will allow you to isolate systematically.
And would be a much more efficient use of your time and efforts in your endeavor.
Your job once you get the schematic is to prove what it is not. A little at a time narrow it down and then voila.
Just one man's opinion.
