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Author Topic: battery not charging... 2E engine in mk2  (Read 1933 times)

Offline tsr_adi

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battery not charging... 2E engine in mk2
« on: 16 March 2013, 19:15 »
The score is this...

When the car is running the voltage goes down slowly as the fuel pump sucks the power, also seeing the same voltage drop at the alternator. I've replaced a dodgy looking earth cable to the battery, also replaced the alternator with a known working one. There doesn't appear to be any fuse in the charging circuit, so should I assume the battery is duff? I can find out this on monday if I take it to work and put our fancy tester on it.
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Offline itavaltalainen

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Re: battery not charging... 2E engine in mk2
« Reply #1 on: 17 March 2013, 00:00 »
how much voltage do you measure with engine running, how much without?

how much voltage is dropped from alternator to battery, obviously with engine running (connect "+" from multimeter to alternator b+ terminal, multimeter "-" to battery plus terminal)?

have you looked at the voltage reg in the alternator at all? does the alternator warning light in the cockpit come on at all (i.e. is it on with the ignition switched on but engine off)?
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2019 Seat Leon ST FR DSG 135kW - eclipse orange - 23k miles

Offline tsr_adi

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Re: battery not charging... 2E engine in mk2
« Reply #2 on: 17 March 2013, 15:20 »
Voltage drop is the same at the battery and the alternator with engine running. It goes down a volt every 30 secondsish, battery light does not come on. The alternator I've fitted is a known working one.
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Offline andyr

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Re: battery not charging... 2E engine in mk2
« Reply #3 on: 17 March 2013, 19:03 »
Might be barking up the wrong tree here, but... Does the battery light come on at all.ie. when first switching ignition on? Just that some cars (but perhaps not the mk II?) The dashboard ign lamp was part of the charging circuit!
Also I would have thought that with engine running a decent alternator should hold a pretty constant charging voltage? Unless the battery was really duff?
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Offline itavaltalainen

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Re: battery not charging... 2E engine in mk2
« Reply #4 on: 17 March 2013, 19:13 »
was gonna ask as well (and have already) does the battery light come on at all?

if the bulb is bust you don't have an 'exciting current' on D+ ....
check what happens if you connect a small incandescent bulb - 12V 2W between D+ and B+ connector on the alternator. does it work then?
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Offline tsr_adi

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Re: battery not charging... 2E engine in mk2
« Reply #5 on: 19 March 2013, 09:54 »
The battery light is not on when running but is on when ignition is on and engine not running. Im fairly convinced its a duff battery so far though...
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Offline itavaltalainen

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Re: battery not charging... 2E engine in mk2
« Reply #6 on: 19 March 2013, 17:44 »
with the latest revelation i agree.... battery most likely candidate.

swap with a mates to test i would say.
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Offline tsr_adi

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Re: battery not charging... 2E engine in mk2
« Reply #7 on: 19 March 2013, 18:51 »
I haven't had chance to put a tester on the battery yet, been off work sick. But I do have another battery lined up if it turns out to have duff cells :)
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