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2012 Fiesta battery light on, rear defrost not working
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Fiesting
New User
Oct 22, 2022, 7:03 AM
Post #1 of 8
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2012 Fiesta battery light on, rear defrost not working
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Hello,
I have a 2012 Ford Fiesta SES hatchback with 167k miles on it.
For the past few weeks, whenever I start the car the battery light comes on after a few minutes and the rear defrost doesn't work once it does. The light comes on whether I start the rear defrost or not, and nothing stops working besides the rear defrost. Has a new battery as of a few months ago.
I don't have much experience working on my own car, but I would like to and if there is any diagnostic work I can do myself I'm interested. Any suggestions?
Thanks all
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 22, 2022, 8:33 AM
Post #2 of 8
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Re: 2012 Fiesta battery light on, rear defrost not working
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Test output power of alternator as RWD is a huge draw item along with blower motor.
Light probably comes on as voltage drops below spec alternator (car is running battery is or should be out of this picture) when volts drop.
You can watch that with a voltmeter in a cig lighter/power port. They make live testers for that or voltmeter (carefully) center inside is bat+ the outside of ports is bat- BTW.
Still check belt is within specs alt could be slipping? Indicator of range of belt wear is on the adjuster if off toss both,
Tom
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Hammer Time
Ultimate Carjunky
/ Moderator
Oct 22, 2022, 9:54 AM
Post #3 of 8
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Re: 2012 Fiesta battery light on, rear defrost not working
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The battery light coming on is not an indication of battery condition.
It is telling you that the battery is not being recharged at the moment. Always a charging system problem.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Oct 22, 2022, 12:44 PM
Post #4 of 8
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Re: 2012 Fiesta battery light on, rear defrost not working
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Yes/no, we don't know amps of battery if they throw a ight momentarily OK, sometimes? If overwhelmed by items that use a lot alternator isn't putting out enough to cover it, battery should for the moments never be so low as to stay on.
Usually unless a serious failure at idle only alternators put out full power at higher RPMs, not that much like 1,500.
Still check the belt if at max to cover stretch normal over long use it will slip, most screech some don't.
It's not really normal ever. Know that CCA of battery is enough new or not it's not eve cold out yet they have less still not normal. If you also have aftermarket items that use lots of power you are in trouble to plain not start (largest draw) so it has to be fixed,
Tom
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Tom Greenleaf
Ultimate Carjunky
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Oct 22, 2022, 1:44 PM
Post #6 of 8
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Re: 2012 Fiesta battery light on, rear defrost not working
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.................. OR when battery so low charging system is putting all AMPS it to recharge not enough for another thing.
To be short it highly needs a battery check if it's a self drain partly inside new or not it's sucking up all alternator can do - not as common most die or don't work new and you know it's NG,
T
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Hammer Time
Ultimate Carjunky
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Oct 22, 2022, 1:57 PM
Post #7 of 8
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Re: 2012 Fiesta battery light on, rear defrost not working
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It just doesn't work that way.
The system reads the rate of charge, regardless of the condition of the battery. It doesn't matter if the battery sucks it all up or none at all.
The light will stay off even with the battery disconnected although that is not recommended.
The3 light can come on if the charging system isn't keeping up with the amount of current being consumed but the condition of the battery plays no part.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Oct 22, 2022, 2:00 PM)
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Tom Greenleaf
Ultimate Carjunky
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Oct 22, 2022, 2:08 PM
Post #8 of 8
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Re: 2012 Fiesta battery light on, rear defrost not working
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Have it your way - I fix this stuff you know! Tom
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