Car wont start - Parasitic Draw?

[Daytones]

Evening All,

Been having some issues with my Leon FR SC 5f 2.0 2013 Diesel Lately and been driving me around the bend!

Last year my car wouldn't start quite a few times due to being on furlough and the battery dying a lot leading to eventual failure, this was replaced in July/august,

Ever since it has been relatively ok,

Roll on the last week...

Drove to GF's on Friday 2nd July in morning and car started fine then as leaving Saturday 3rd July in morning it would not start without my jump pack so 24 hours sitting just gave up.
Went back to GF's on Sunday 4th July in morning and car started fine again no problems, then we went away for 3 days and left my car at hers, come Wednesday 7th July morning (been left 3 days) it starts up fine again and make a 100 mile trip, again on Thursday 8th july morning starts fine drive another 100 miles then back 100 miles on the Friday 9th July with no issues, didn't use car on the Saturday 10th July but Sunday 11th July morning boom wont start again...

Went out this morning and it did start properly but the randomness is infuriating me as every time it does not start I have to get jumpers out...

I had a local garage with my assistance looking at this today, we decided on doing a parasitic draw test, we found when everything off and car doors closed etc there was something drawing 0.176 MAH? when apparently should be 0.03~ is this correct?
Anyway - we carried on, we tested the alternator and that was doing 14.7 volts, we disconnected the alternator and it was still drawing the same 0.175mah so it wasn't the diodes or whatever they are? We disconnected the starter motor to check that wasn't at fault and it was still the same draw no change.

we pulled every fuse in the glove box with no change, then we pulled fuses from under the bonnet and only 1 made a difference... its a 7.5 amp fuse, however the listing for it I get compared to what the garage gets is different, from my gathering it says the fuse is Engine Control Unit but on theres it says its something to do with ABS/ESP system, but as soon as this fuse is pulled it goes to 0.03 as it should be?

From the diagrams i could see it is fuse number "17" if anyone gets any different layouts? its a leon 5f sc fr 2013

After spending a good three hours troubleshooting etc just could not figure out what the fuse is for / meant to do / how to troubleshoot any further, Wondering if anyone on here could shed some light on whether A: fuse 17 under bonnet is for ECU or the ESP/ABS on my model 2013 or something totally different, and B depending what it is what else could we possibly check, as its alright owning a "nice" car but if it doesn't start its basically a paperweight...

Many thanks

Damon.

 

[RUM4MO]

My take on this is, that fuse that you are removing is for a controller and that controller is controlling power feeds to some users, all you are doing is not making it possible for current to be draining. I've been there done that but in my case the root cause seemed to me to be a S/W issue, ie all the "meant to be" power feeds were not being put and kept asleep. That is the job of the BCM and internet chat suggested what I was seeing was a known issue, but only to a few people - and only initially discovered many years before that, I'd doubt if that is your issue.

After closing all openings, or at least tripping the door locks to fool the car into thinking everything is closed, you need to wait maybe as long as 20 minutes - did your mechanic do that. Next you need to cut into the 12V power system at the battery without re-waking the car's systems back up, did he do it that way and how was it done to achieve cutting into the 12V system without re-waking the car?

Going back to what I said initially, what I was meaning was, the BCM controls lots of consumers around the car, removing a consumer's feed fuse will stop it being able to draw current - but so will removing the fuse that powers the BCM, so that can lead to confusion.

Most extra unwanted current draws will be due to a wiring issue, trapped/nipped or chopped wires, or a system fault, was that car scanned with a proper VW Group fully compliant scan tool - that is the starting point as well as knowing everything in the car functions as intended.

I know the feeling wrt "will it" or "will it not" start, a completely useless situation, with my daughter's late 2009 Ibiza, I monitored and investigated that car for about 18 months after my first SEAT dealership poo pooed my "is it just a BCM S/W issue" 18 months later and using another SEAT dealership who gave me credit to thinking it was just a known (but forgotten about) BCM S/W issue, lead to that car being brought back to being reliable again! Not your problem though I'd think.

 

[RUM4MO]

Another maybe useful thing to do is to buy one of these cheap digital volt meters that plug into the 12V power socket (ciggy lighter in the past) and make a habit of glancing at it from time to time to give you confidence - or not, that the battery and charging system are doing what they should be doing, very easy and cheap to buy roughly £5,with this sort of problem you need all the info you can casually collect while using that car as normal just so that you or a garage does not miss something easy and just not cram money into fixing areas that are not broken as you desperately try to escape from this annoying situation.

 

[Daytones]

Afternoon, so I purchased one of these 12v usb charger monitor things for the cigarette adapter, I did a long trip today around 120 miles round trip, most of the time it was showing 13.1 volts and occasionally it was jump up to 14.6 for literally 5 seconds then back down ( I had Aircon on, radio and have virtual dashboard ) when I arrived home I turned Car off then turned key into ignition with radio on and dashboard it starter at 12.6 volts then every 10 seconds it would drop a .1 volt so after about a minute it was at 12.1 volts so turned ignition off...

Would this potentially suggest my alternator is broken? Or the regulator? Or potentially a bad ground? I did look at the battery ground and it looked ok to me but may need to get garage to check it out better.

Many thanks.

 

[mty12345]

Afternoon, so I purchased one of these 12v usb charger monitor things for the cigarette adapter, I did a long trip today around 120 miles round trip, most of the time it was showing 13.1 volts and occasionally it was jump up to 14.6 for literally 5 seconds then back down ( I had Aircon on, radio and have virtual dashboard ) when I arrived home I turned Car off then turned key into ignition with radio on and dashboard it starter at 12.6 volts then every 10 seconds it would drop a .1 volt so after about a minute it was at 12.1 volts so turned ignition off...

Would this potentially suggest my alternator is broken? Or the regulator? Or potentially a bad ground? I did look at the battery ground and it looked ok to me but may need to get garage to check it out better.

Many thanks.

Many of these modern cars have 'smart alternators' that vary the voltage as needed. Are you sure it isn't just another bad battery that can't hold it's charge? I don't see how the voltage could drop so quickly from 12.6 to 12.1 if the battery is good. I know it's not that old, but that's quite strange IMO

 

[Daytones]

Well on the 13th July the day after I posted the original issue I did have RAC come out who provided my new battery last year and he did the checks they do and battery health was showing as good on their system as it is under warranty with them but won't change it if it's showing as good.

 

[mty12345]

Well on the 13th July the day after I posted the original issue I did have RAC come out who provided my new battery last year and he did the checks they do and battery health was showing as good on their system as it is under warranty with them but won't change it if it's showing as good.

Yeah, i mean it's unlikely a new battery would go bad in such a short space of time, but I also can't see how the voltage could drop so quick. Maybe you should check at the battery terminals with a multimeter, rule out the cigar lighter thing giving an incorrect voltage.

 

[Daytones]

I did but didnt show anything, but as an update a replacement battery was required, the warranty one that I got was found at fault and not had the issue since!

 

[martin j.]

Even new batteries can fail if stored incorrectly before fitting, ie, on a stone/concrete floor or steel shelf, why I don’t know, many folk test the battery with a simple volt meter were it should be tested with a load drop test meter to give it a work out as per real life. At least your are sorted now.

 

[RUM4MO]

Modern battery testers has a less aggressive method of testing than slapping a heavy/typical load across them. It seems like most versions of modern starter batteries don’t much care for the abuse a traditional dropper test imposes on them - so it has been said, and as I have a smart(?) battery tester, I only ever just use that and it seems to work okay for me.

 

[martin j.]

I have access to both types of tester but my point was a simple voltage reading will only give so much information, it’s not the voltage that kills you it’s the power. Sorry if I worded the post badly, waiting for the rugby to begin on telly and in a rush.

 

[RUM4MO]

I am under the impression that modern battery testers do more than just take a straight voltage measurement and guess the CCA from there, if that was the case it would just be a case of specifying a high input impedance DVM and a chart of estimated CCA against rated CCA wrt terminal voltage, there are plenty warnings out there advising against the use of "load dropper" testing with modern EFB and AGM batteries - I get that impression that that old method worked while nothing else existed, but times have moved on so more modern safe and accurate method have been evolved and are now the accepted standard.
The CTEK one that I have has been designed by Midtronics, who are a market leader in this sort of thing, for CTEK, so that is good enough for me and I trust the results I get from my battery tester.