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Battery goes flat in less than a week


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6 replies to this topic

#1 mondeo df

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Posted 05 March 2021 - 08:50 PM

2005 Hatch 2.0 petrol auto.

 

As the title says....Battery goes flat in less than a week.

 

Last winter the battery kept going flat.

 

Bought a new one and all was well.

 

The alternator cooked at the end of last summer. Literally.

 

I fitted a used alternator and all was well.

 

Since the weather got colder the battery flat issue returned.

 

Got the battery swapped under the 5yr warranty.

 

2 weeks later and dead battery.

 

The car is only used 2-3 times a week at most. But that's enough to avoid the problem

 

If it's left for a week it's flat.

 

Tomorrow I'll stick the ammeter in the supply lines and see if I can tell where the power drain is but wondered if you guy's could tell me the likely causes / suspects.

 

And... although I'm sure the alternator is doing it's job of charging, could it also be the source of the drain?

 

Cheers for any advise.


Edited by mondeo df, 05 March 2021 - 08:50 PM.


#2 raynkar

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Posted 05 March 2021 - 09:18 PM

What make and type of battery do you have?

Is it a silver calcium type and not a lead acid battery?


You can put your vehicle info at the bottom of your posts to give details to help others know what you drive :)

#3 PURPLE_2L_LX

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Posted 05 March 2021 - 10:27 PM

Yes alternators can drain the battery if faulty,  boot light staying on

or the map lights etc?

 

Aftermarket stereo staying active?  Anything plugged into the lighter sockets?

 

Towbar fitted?


MK4.5 TDCI 140 Business Estate.

 

MK3 FUSE INFO CLICK HERE ... FORD WIKI CLICK HERE .... FORD ETIS CLICK HERE

Adding your location may find someone local who could offer assistance.

F-Super, Bluetooth OBDII (ELM) and a MS509 scanners (test subjects required).

ForDiag now available to victims.


#4 mondeo df

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Posted 05 March 2021 - 11:04 PM

What make and type of battery do you have?

Is it a silver calcium type and not a lead acid battery?

 

It's the silver type.



#5 mondeo df

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Posted 05 March 2021 - 11:05 PM

Yes alternators can drain the battery if faulty,  boot light staying on

or the map lights etc?

 

Aftermarket stereo staying active?  Anything plugged into the lighter sockets?

 

Towbar fitted?

 

Yeah, checked the boot light, and all other interior lights. Got the original Ford stereo and unplugged the ciggy lighter.

 

No towbar.

 

Has got aftermarket rear parking sensors. Will look at those.

 

What tests can I do on the alternator?


Edited by mondeo df, 05 March 2021 - 11:07 PM.


#6 PURPLE_2L_LX

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Posted 06 March 2021 - 02:34 AM

You need to check the diodes in the alternator, they normally block the flow in one

direction from the AC output. When they breakdown they allow current to pass

backwards which drains the battery.

 

Battery/alternator test...  http://www.talkford....test-procedure/

 

Do that test so we can see if there are any obvious issues.


MK4.5 TDCI 140 Business Estate.

 

MK3 FUSE INFO CLICK HERE ... FORD WIKI CLICK HERE .... FORD ETIS CLICK HERE

Adding your location may find someone local who could offer assistance.

F-Super, Bluetooth OBDII (ELM) and a MS509 scanners (test subjects required).

ForDiag now available to victims.


#7 mondeo df

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Posted 06 March 2021 - 05:36 PM

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OK... found it.

 

Did all tests as above but nothing showed up.

 

So... I put the ammeter between the battery live terminal and the live clamp, so any current flowing had to go via the ammeter. Nothing could escape.

 

Found I had wildly fluctuating current between 25mA and 60mA. Not what I was expecting.

 

Did the same check on my Mondy (this is the wife's Mondy) and had rock solid 16mA (locked or unlocked)

 

So, back to the wifes car and I pulled each fuse in turn till the current dropped to a solid 16mA.

 

A-HA!!! F28.... 20A supplying the ignition switch.

 

Put the fuse back and pulled the plug off the ignition switch... no change.

 

Pulled the fuse box out to see if there was any corrosion or a fried spider or worse.... nothing.

 

According to Haynes there was nothing between F28 and the ignition switch except a 1.5mm red. Nothing else supplied by F28.

 

So I chopped the cable about 3" from the fuse and 3" from the ignition switch and crimped in a new cable (I used some 1.5mm flex and left it double insulated)

 

BINGO!!!!!

 

16mA solid. Everything working as it should.

 

Without stripping the loom to try to find exactly what and where, I'll never know quite what was going on but at least it's sorted.

 

Brownie points in the bag and a well earned day down the man cave tomorrow!

 

I hope this will be useful to somebody some day.


Edited by mondeo df, 06 March 2021 - 05:39 PM.

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