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Coupe Deville
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Discussion Starter #1
Hey guys. Hoping someone can shed some light on this issue I'm having. So the battery in my 1970 coupe Deville keeps dying. I change the alternator but still keeps doing it. It's like it stays in all the time even when the key is off. I can still operate the power windows and stuff. When the car is running I removed the positive off the battery and the car shuts off. Usually it's a sign of a bad alternator but that's new. I'm confused
 

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1970 Coupe De Ville//Cessna 172
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551 Posts
Yes. If it is running and you disconnect the battery and it dies, it is usually the alternator. You xon't say if it drains while sitting overnite or if just when in use.
 

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Coupe Deville
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Discussion Starter #3
Jeff R said:
Yes. If it is running and you disconnect the battery and it dies, it is usually the alternator. You xon't say if it drains while sitting overnite or if just when in use.
Sorry Jeff. It dies when sitting for a a couple of days. Not while running. I just changed the alternator but that didn't fix it.

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Could it be the regulator? Didn't change that
 

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87 Brougham, 1969 Calais, 95 FWB, 07 SRX, 07 ESV
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Re: 1970 coupe devilleCar drains battery

if it drains after sitting for a few days then you probably have some parasitic drain going on.
Unhook one side of your battery (doesn't matter which, I usually do neg) and hook a multimeter up between the battery post and the battery cable. If your amps (draw) is high (not sure what a 70 should be...I'd guess 50 mA, but no more than 100 mA) then you have a drain.
You can then start pulling fuses until the drain goes away. That will tell you what circuit is draining your battery and you can then chase that circuit to find out what exactly is causing it (shorted wire, bad component, etc)
 

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1970 Coupe De Ville//Cessna 172
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Couple of thoughts..... As the previous post says, disconnect the battery. But leave it disconnected overnite/couple of days. If it is still going dead then you have a battery issue. Have to determine if it is the car or the battery. Or, you can swap out your battery with one from another car and see if it still does it. I am thinking battery because a good, fully charged battery should be able to start the car and keep it running for a while. Hiwever the fact that it dies when disconnected makes me rethink that. Keep us updated.
 

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1965 Sedan, 1969 convertible, 71 Fleetwood, 74 Coupe
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Re: 1970 coupe devilleCar drains battery

Both my 65 and 69 had power drains, the 65 turned out to be the power seat switch stayed on, The 69 we never found so i put in a battery isolating switch $(KGrHqF,!jcE9KySKwZNBP,1gFBT8g~~60_35.jpg
 

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Coupe Deville
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Discussion Starter #7
Here's an update of what I found today.

Took the car to work today, all went well. Got home and started messing with the fuses. They all seem to be ok except for the one that is labeled wipers. I put a volt meter on the poles with no fuse and it read 12 volts. It has a 25 amp fuse and was burnt. All this with engine off and switch on off position. No key in the switch. Kept checking and realized my power windows always work key or no key which I thought was odd unless it's a Cadillac feature that I don't know about. Those were the two fuses that read 12 volts all the time. Everything else read zero even when car is running which I also thought was odd. Any ideas?
 

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1970 Coupe De Ville//Cessna 172
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Pull them both and let it sit. Still think you should disconnect the battery and let it sit
 

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Coupe Deville
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Discussion Starter #10
Jeff R said:
Pull them both and let it sit. Still think you should disconnect the battery and let it sit
I disconnected the battery and checked the voltage tonight and the battery is holding charge.
 

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87 Brougham, 1969 Calais, 95 FWB, 07 SRX, 07 ESV
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probably a short in the power window circuit and maybe the wiper one. I'm pretty sure with the key out there should be no power going to either of those assemblies so I'd start looking into those.

On my 69 the power window circuit also drains the battery. I haven't tracked down the problem yet so I just pulled the fuse for that and when I start the car I just put the fuse back in.
 
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