wtf is wrong with my electricals?!
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Junior User
Joined: Mar 2012
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wtf is wrong with my electricals?!
So as some of you pay have seen in my last thread, it appeared the starter went out on my 78. finally got the starter out today, and went and got a new one. put it in and nothing changed....
Oh and to make things even cooler, my batery holds a charge just fine, but as soon as i turn on the smallest thing, even just parking lights, voltage dives straight to almost 0, and when i turn whatever it was off, it comes right back to 12.6.
Oh and to make things even cooler, my batery holds a charge just fine, but as soon as i turn on the smallest thing, even just parking lights, voltage dives straight to almost 0, and when i turn whatever it was off, it comes right back to 12.6.
Posting Guru
Joined: Sep 2009
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From: Suburbs of Chicago
How are you testing to see your battery's voltage? Post to post? It almost sounds like your checking your available voltage in such a way that you are almost doing a voltage drop across a switch or something. Switch open, you would have B+ on the meter because that is what is at one side of the switch and you have no power only ground potential on the other side. Switch closed, you're only measuring voltage drop across the switch.
How old are your battery cables? Give em a good tug and see if the cable comes out of the end. I've seen a battery cable that will let a weeeeee lil bit of current flow, but it don't matter how much current, it will still look like 12.6 volts!
I know its not your biggest problem right now, but did you test for voltage drops to/from the starter before you dropped it?
How old are your battery cables? Give em a good tug and see if the cable comes out of the end. I've seen a battery cable that will let a weeeeee lil bit of current flow, but it don't matter how much current, it will still look like 12.6 volts!
I know its not your biggest problem right now, but did you test for voltage drops to/from the starter before you dropped it?
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Junior User
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I just had a multimeter on the +/- of the battery. and the voltage doesnt just drop immediately it just goes down really quickly to like 0.2 volts or something like that when i turn the starter, and like 0.6 when i try to turn the headlights on. it even drops to like 2.5 just by turning the key to the on position so the fasten belts light comes on
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Junior User
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the posts are pretty damn clean but i guess ill go get my baking soda and wire brush, see if it makes a difference
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Lead Driver
Joined: Mar 2010
Posts: 5,250
Likes: 11
From: West Virginia
pull your grounds and clean them with a wire brush and contact cleaner, then replace them and smear them with dielectric grease to prevent corrosion. Could be a bad ground. You need a good ground from the battery to the frame and the engine block to the frame, for starters. The body needs to be grounded too, and while it should ground through the mount bolts its not a bad idea to throw a strap from it to the ground as well.
I think you need to take your battery in to the parts store to have it load tested. I've had batteries to the exact same thing ... they hold voltage and the minute even a small load is placed on them the voltage drops through the basement. Turned out to be a bad cell once the battery was load tested.
I think you need to take your battery in to the parts store to have it load tested. I've had batteries to the exact same thing ... they hold voltage and the minute even a small load is placed on them the voltage drops through the basement. Turned out to be a bad cell once the battery was load tested.
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Junior User
Joined: Mar 2012
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the battery has been load tested and its good. i think my cables are bad. when i have it hooked up to jumper cables, the negative cable goes to the engine block and it does the same thing. but im just gonna replace my solenoid, cables, and battery terminal clamps, see if it helps at all.
MSEE
Joined: Apr 2004
Posts: 10,386
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From: Austin, TX
There's no way your battery can pass a load test if it drops from 12 to zero with the starter connected. That's the definition of failing a load test.
Bad battery cables and connections place a voltage drop in between the battery and the load, leaving less available voltage for the load. According to your measurements, you don't have voltage to begin with. It sounds like your battery is shot - you may have other problems on top of that, but no amount of parts you throw at it is going to fix the source. I would believe your cables were bad if you were taking this measurement downstream of the cables - but you said you're taking the voltage across the posts. That takes any drop due to bad cables out of the equation.
The starter solenoid has nothing to do with the problem. You even mentioned you see the same behavior whether the load is the starter, or the headlights. The headlights have nothing to do with the starting circuit. The battery should be able to maintain cranking voltage across the posts regardless of the condition of the battery cables downstream. You've verified that your battery is NOT doing this. That's why your battery is shot.
Bad battery cables and connections place a voltage drop in between the battery and the load, leaving less available voltage for the load. According to your measurements, you don't have voltage to begin with. It sounds like your battery is shot - you may have other problems on top of that, but no amount of parts you throw at it is going to fix the source. I would believe your cables were bad if you were taking this measurement downstream of the cables - but you said you're taking the voltage across the posts. That takes any drop due to bad cables out of the equation.
The starter solenoid has nothing to do with the problem. You even mentioned you see the same behavior whether the load is the starter, or the headlights. The headlights have nothing to do with the starting circuit. The battery should be able to maintain cranking voltage across the posts regardless of the condition of the battery cables downstream. You've verified that your battery is NOT doing this. That's why your battery is shot.
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Junior User
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Okay well I hooked up jumper cables to the battery from a running car and when I turn the key nothing happens. The starter does not even turn. But its places some in normous load on the running car and I watch the voltage meter drop down very low and all the lights go super dim. I tested the battery with our snap on battery tester/charger that we have at our shop. Battery is 850 cca and it tested at 795cca.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Okay well I hooked up jumper cables to the battery from a running car and when I turn the key nothing happens. The starter does not even turn. But its places some in normous load on the running car and I watch the voltage meter drop down very low and all the lights go super dim. I tested the battery with our snap on battery tester/charger that we have at our shop. Battery is 850 cca and it tested at 795cca.
Lead Driver
Joined: Mar 2010
Posts: 5,250
Likes: 11
From: West Virginia
I would tend to agree. If you have another vehicle I'd try swapping the batteries and seeing if it helps. If the problems follow the battery then replace the battery. Although I did have a small car battery hooked to one of my trucks for a while just as a temporary thing (was not a dd) and if it didn't start the truck on the first couple turns, the battery would give up pretty quickly. There is a reason our old trucks specify a larger battery than most cars..