How to detect an electircial draw?


Old 12-02-10, 11:21 AM
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Location: New York, United States
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How to detect an electircial draw?

Have a 97 Lincoln town car, had new battery put in last January, went away for a few weeks and came back, no power at all. Got a jump, took it in, they said the battery was fine but issue might have been a bad connection which I assumed they repaired. Never had an issue while car was being operated for the next few monhs; then when spring came I disconnected the negative wire since the car would not be used for five months; when I returne, car started right up. My question is this; is there a way of detecting an electrical draw on a car when everything is off to see if something still is drawing current? Only thing we can think of is that the radio was replaced with an after market radio and disc player, but there is a power source button on the radio that turns it off. If button is left on, radio also shuts off with ignition. I left the car for two weeks, battery was connected and when I returned there was no power to even light the interior lights.............something and I do not have a clue must be drawing power. Any help will be greatly appreciated.
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Old 12-02-10, 11:40 AM
Join Date: Mar 2009
Location: Texas
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These days there is always some draw on newer cars due to computers, security systems etc. but they normally only impact a battery after the car has been sitting for several weeks/months. To start with a simple approach first, is there any chance that glove box, or trunk lights are not shuttiing off for example?
Old 12-02-10, 12:17 PM
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Your electrical drain is called a parasitic battery draw. Here are a couple of helpful links

How to Find a Parasitic Battery Drain |

How to Find a Parasitic Battery Drain - wikiHow
Old 12-03-10, 04:47 PM
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To start with a simple approach first, is there any chance that glove box, or trunk lights are not shuttiing off for example?
We have a girl at work , that we keep around for the express purpose of locking her in the trunk to make sure the light goes out

After 2 weeks of no use, your battery is completely entitled to be dead....Especially on a high end electronic vehicle......Your radio presets, PCM memory, Memory seats, or just about anything else you have to reset after a jump start causes a draw on the battery. Add them all together, and Yes, it will kill a battery in two weeks.
Old 12-04-10, 03:47 AM
Join Date: Mar 2009
Location: Texas
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Uncle, that is not really why you keep the girl around is it? I have never seen a good battery drop that low in only just 2 weeks. We would move new cars around the world on ships and they would still start up after 4 or 5, or even 6 weeks. We had a bigger problem with tires losing air pressure and always had to over inflate them before shipment for that reason. The batteries would go flat but only after about 2 months of sitting around. I think there is something else going on with this vehicle around parasitic battery drain as Diane 1 suggested.
Old 12-07-10, 09:50 AM
Join Date: Feb 2005
Location: USA
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Check the lighted mirrrors on your sun visors. A faulty or closed switch there will do it every time.
Old 12-07-10, 10:05 AM
Join Date: Sep 2005
Location: York haven
Posts: 111
The computer draw should be just so much.. Exactly how much I do not know, its something like 0.05 amp. If it is appreciably higher then start troubleshooting, which consists of disconnecting things.
This figure must be in the manual, if not, then we need better manuals.

Measure using an ammeter at the battery..
As to the girl...we need to train mechanics from birth, including girls.

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