Battery causing dash lights

2004 Sable. Have replaced 3 batteries and the alternator. Looks like have to get yet a 4th battery. Works great for about a month then my dash lights will come on abs brake light engine and gas cap and sometimes my Info like mileage trip info ect will not come on. Not long after battery will not start car without a jump! Starter perhaps? Help!!

What battery voltage reading are you getting when the engine is running?

Just some thoughts to start with. I would check the ground and all wires and connectors for being loose, chaffed, cut or burnt. you might be getting an intermittent connection somewhere causing it to be able to charge the system sometimes and other times not.
also check to see if your brake lights are staying on intermittently when the vehicle is parked. a bad brake light switch can cause the brake lights to stay on when parked sometimes and other times it will work fine. especially if you start your car in the morning and the battery seems a little weak and later in the day it starts fine. I think with a new battery it is possible the brake lights being on might not totally kill the battery overnight. with an older battery it will.
Also, it is possible that you got a bad alternator if it was a rebuilt or remained one.

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13.7im getting 13.7 not under load. Under load 12

It was a brand new battery and brand new alternator not rebuilt

13.7 and under load 12

Also could it possibly be too small a battery. It has been 640 cranking amps

Those numbers are on the low side, especially the 12 volts one. As weekend warrior noted, the alternator may not be performing up to snuff. Even the ones that have just been bought can be bad.

Under how much load? At idle the alternator should be capable of 60 to 90 amp output, depending on alternator size.

A charging system malfunction does not necessarily mean a failed alternator. Batteries can be recharged, they don’t wear out in a short period of time just because of discharge.

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Battery voltage while the engine is running just tests the voltage regulator, not the alternator output. Voltage regulators specs at idle (warm) can be close to 12.0 volts on the low side but you would need to look up the spec on a 2004 Sable to be sure. You need to have someone that understands how to perform an alternator output test perform one. The fact that 3 batteries and an alternator have not fixed this, it’s likely neither of those are the issue. A new alternator can be bad but you need to have the amp output tested, not just the voltage. Don’t just replace it. The fact that it happens consistently after a month is more likely due to be a parasitic draw. That’s easy to test for. Set your multimeter on 200 mA setting if it’s not auto ranging. Disconnect negative battery cable. Connect one lead to battery post, the other to the disconnected cable clamp. Wait a few minutes to make sure all electronics have gone inactive (they turned on when you connected the leads). Take a reading. You should have less than 50mA (.050A). If it exceeds that, you have a drain somewhere and will need to start pulling fuses to isolate which circuit has the draw.

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On some vehicles, it can take over an hour before computers/modules go to sleep before you can test for a parasitic draw.


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Yeah, but on a 2004 Sable?

And this on a 98.


Please read your link. Unless I’m blind, there is nothing in there from the technician that said to wait for any particular amount of time. The customer said they waited with “Everything off for several hours”. I recently had an '08 Corvette and a '13 Civic that had parasitic drains in the shop. Both went quiet after a few minutes. So, based on my experience, an '04 Sable will do the same. Might I be wrong? Sure. Do you have any experience diagnosing parasitic draws that leads you to believe a 2004 Sable will take longer than a few minutes? If so, please provide details of the year, make, and model. I’m always willing to learn.


Ok thank you I’ll give that a try

The alternator only putting out 12 volts when the engine is idling makes me think the problem is most likely the charging system, not the battery or phantom current discharge. The alternator electronics may actually think it is outputting more than 12 volts, but some of the voltage is being lost in faulty grounds. First test I’d do in that situation is to measure the voltage from the alternator case (which should be grounded to the chassis ) to the battery negative post (which should also be grounded to the chassis) when the alternator is only putting out 12 volts with engine running. Since both should be connected to chassis, I wouldn’t expect you’d measure more than a few tenths of a volt. What do you measure?

Suggest to also explain what you mean by “under load”? Do you mean electrical load; i.e. the headlights are on bright? Or are you referring to an engine load, like driving uphill?

By load i mean yes electrical. Lights ac ect. Im going to test the alternator now

Im i testing while its running?

Remember that some fords and others if the voltage drops below X volts the alt will go into a failsafe mode and not charge, so make sure the battery has a good charge before testing the alt…