Parasitic Battery Drain

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Chris4564
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Parasitic Battery Drain

Post by Chris4564 »

Hi - I've searched the forum and not found an answer. New (to me) MK3 has a constant drain of 0.37A which obliviously drains the battery over a couple of days without use (or overnight if it isn't charged). I've done the usual test by hooking up an amp meter and pulling fuses and relays one at a time but didn't find the culprit :w_tf: . Are there any fuses anywhere other than the boxes in the Frunk & Engine Bay and behind the dash on the passenger side?

Also discovered the battery retaining strap hidden in the frunk but can't see what it bolts to in the engine bay, there is a pillar behind the battery with an eye for the hook but nothing in front?

Any help appreciated!
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jimi
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Re: Parasitic Battery Drain

Post by jimi »

0.37A shouldn't flatten a good condition correctly sized battery in a couple of days, a week maybe.
What capacity and condition/age is the battery ? It probably isn't just one thing that is pulling the current, may well be a combination of small loads. Try pulling the fuses one at a time (don't replace them) while monitoring the current with your meter. Also try disconnecting the alternator, both the plug and the main lead ( disconnect the battery better taking the main lead off, then reconnect. make sure the lead can't touch anything, it will be live)
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Re: Parasitic Battery Drain

Post by jeff »

0.37a x 24 hours is 8.88 amps per day in my rough laymans estimate

60 amp battery should be good for a week if my figures are correct
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Re: Parasitic Battery Drain

Post by Chris4564 »

Hi thanks for the replies, given that I can't confirm the battery condition I've ordered a new battery to give me a better baseline although only a 45AH as the 60 that was recommended as an alternative is too large for the battery tray, we'll see how that goes. Once that's in I'll retest as you suggest.
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Re: Parasitic Battery Drain

Post by jimi »

IIRC the MK3 has an odd battery size, unlike the MK1 & 2
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Re: Parasitic Battery Drain

Post by JD1 »

Hi had the same problem on my late mgtf and in the end I changed the alternator with reconditioned one which solved the problem.

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Re: Parasitic Battery Drain

Post by Topdownman »

The rear fixing for the battery strap is a hook on one end and a threaded section on the other which hooks under the battery tray and tightened up with the nut through the strap. You could probably rig up a temporary support using the strap and some zip ties, not good to have it unrestrained.

I am sure J-Spec would have a suitable spare part for you.

I think there are only the 3 fuse locations you mention.

Hopefully your new battery will resolve the problem.

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