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Flat battery after wiper motor change.

E

EP3PO

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128
Yesterday I had the rear wiper motor replaced by a garage. Drove home fine, this morning I went to start the car and it did start but it sounded like the battery was almost flat, drove to work thought nothing more about it. When leaving working the battery was flat, it turned over once but didn’t start.

I am sure that there is an electrical fault with the install of the new wiper motor. How can I check if something is draining the battery? I have a multimeter, if set it to amps and run it in series with either the positive or negative battery cable, what sort of reading should I get when the car is unlocked but nothing is being used? (I’m sure it’s not going to be as simple as 0 amps)
 
As a quick update I have a flat battery (still showing 12.3v though) so a parasitic draw test is difficult but I am getting 70 milliamps with no load. Is this correct? I would have thought I should get an absolute max of about 50 milliamps. The annoying thing is removing the rear wiper fuse makes no difference, so I'm not sure its a fault with the rear wiper motor. I am sure the problem is because of the work done yesterday but I'm not sure what. I am charging the battery now, I will check again in a couple of hours.
 
I'd have tried checking the voltage with and without fuse. Hard to know what the draw should be, depends on your headunit and so on.

As far as I'm aware there is no constant live to the wiper motor, (or rather, the ignition breaks the circuit) so it should only be able to draw when the ignition is on. Unless it's been crossed with the live for brake lights or something I'd guess they just drained it whilst working on it
 
Last edited by a moderator:
CTR_Nick said:
As far as I'm aware there is no constant live to the wiper motor, (or rather, the ignition breaks the circuit) so it should only be able to draw when the ignition is on. Unless it's been crossed with the live for brake lights or something I'd guess they just drained it whilst working on it
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Cheers, I am going to try fuse by fuse to see if I can find anything. The battery was fine when I left the garage, and I have driven it for two half hour bursts before it went flat. I know this now sounds like the alternator, however after I have driven it for 30 mins I can start it 4 times before its it drained (and it was totally flat before the drive). However if I leave it for 12 hours the battery goes flat.
 
Yeah, there something shorting it then. The alternator is obviously grand. If you can't find it I'd just unplug the battery when you get to work tomorrow. Might see you away! :lol:


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When was the battery last replaced? It might be holding _just_ enough charge after a drive but be otherwise failing. Also, not sure if there's a way you can check the ELD, normally it codes if there's a problem but I guess it's possible for it to fail in a way it wouldn't.
 
I have fully charged the battery now. I am going to leave the battery connected over night to see if it goes flat, I have a battery booster so I will definitely be able to start it the morning and get to work (yippee!).

Battery is 6 years old. About 6 months ago I was curious about the battery's health so I checked it with a multimeter - I can't remember the check it was something like leave the car for 48 hours then check the voltage and if its above 13.4v (or something) the battery is golden. It passed with flying colours so I am not convinced this is the issue, but I bet that's what the garage will tell me tomorrow.
 
Batteries are always spot on until they finally go!! :D 6 years is a good run on one!


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Another quick update, battery completely flat this morning after being 100% charged last night. The garage suspects it’s a dodgy battery but does a bad battery lose all its charge over night? I have had battery’s go in the past and normally I have got 2 weeks of sluggish starts before it won’t start. Then a full charge buys me at least 3 days to get it changed. I am sure that there is something draining the battery and all changing the battery is going to do is buy me a week until its drained then I am back to square one.

All this is too coincidental that the wiper motor was changed on Wednesday and now I am having serious issues (no issues what so ever before).
 
You could unplug the rear wiper motor and try again to rule it out?

But I would imagine if one or more of the cells has gone in the battery it would discharge pretty quickly.
 
Cheers guys,

UPDATE: Garage says that the earth strap that links the engine/gearbox under the car is corroded and causing the parasitic draw on battery. The garage tried to remove a heat shield last time it was in as it was rattling between 3k-4k revs. Do you think this is linked? The earth strap will cost £65+ VAT plus hour fitment.

By the way they didn't fix the rattle!
 
I wouldn't like to guess really. Suppose it's possible to damage the cable if you're ripping a heat shield out. What has corroded on the strap? Doesn't really make sense for the earth to corrode and cause a draw.


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Krzys said:
If the earth was bad the car wouldn't run (talking main earth to the battery though).
Click to expand...

Yea car runs fine. They have specifically said this is the earth under the car, I am trying to find photos of it to better understand. I don't think this is the earth that goes to the battery terminal.
 
What is the earth under the car? I thought the engine earth was on the top left. Maybe a strap between gearbox and engine block?


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Another update. It was the main Earth/Negative battery loom that was replaced. Its the one that goes from the batter -ve to the body work and then has a long wire that goes down under the engine somewhere. It was the bit that is under the engine that the garage said was corroded.

The battery went flat again over the weekend. Garage is checking the health of the battery now to rule this out.
 
OK so new battery fitted, but is the wrong battery so has the +ve and -ve on different corners. So now the bonnet stay rests on top of the positive terminal of the battery when down. There is a plastic cap on the battery and the end of the bonnet stay so the risk of a short is small I think. But I don't like things being perfect. What your thoughts on this? I will try and post a photo to better explain.

On the plus side this should be the end of all my flat battery issues.
 
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