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Discussion Starter · #1 ·
Happy new year all.
I am having a nightmare of a problem with my 2014 Aventador Roadster with start stop for over a year now.
It all started with the car not starting when I press on the start button. AlI I heard was a
‘Click’ and dash had ‘start stop fault. System not ready’.
Installed new battery, new super capacitor and new trickle charger and every time we thought the problem was cured, it comes back again.
I tried giving the car a start up yesterday and the problem came back. I’m at my wits end as to what the root cause of the problem is.
if I remove the positive (red) cable on the supercapacitor that goes to the starter motor and connect it directly to the positive terminal of the battery, the car fires up. (By doing this, it is the car battery that starts the starter motor rather than the capacitor). This surely proves my starter motor is ok?
We have checked all the wiring, clean all electrical contacts etc….and the problem still persists.
Any help or advise us greatly appreciated. Might need to send it to the dealer for a proper diagnostic plug in??
 

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I had a starting issue with mine a couple years ago. Replaced the battery, was ok for a while then, battery died again. According to the dealer, they found a wire under the drivers seat making contact with something it shouldn't have been. This was causing the battery to be drained slowly.
 

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Discussion Starter · #3 ·
I had a starting issue with mine a couple years ago. Replaced the battery, was ok for a while then, battery died again. According to the dealer, they found a wire under the drivers seat making contact with something it shouldn't have been. This was causing the battery to be drained slowly.
Thanks for the reply Brian.
Does your Avantador has the start stop? Also, I have the trickle charger on the car when it’s not in use….shouldn’t it compensate the battery if/ when it’s draining?
 

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Thanks for the reply Brian.
Does your Avantador has the start stop? Also, I have the trickle charger on the car when it’s not in use….shouldn’t it compensate the battery if/ when it’s draining?
It does have start/stop. I was not using the trickle charger at that time. I agree the charger would compensate but maybe not fully keep up with the loss.

by the way, mine is a 14 as well.
 

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I just found the receipt from the dealer. This is after a new battery had been installed. Here are their notes:

"Battery one cell down. Investigate and found draw. Track down draw to panel fuse and found breaker driver seat over hot. Disassemble driver seat and disassemble side command switches. found harness rubbing short on metal part. Repair harness on side panel switches and put harness in correct plastic guidance. Test and no more draw"
 

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Discussion Starter · #6 ·
I just found the receipt from the dealer. This is after a new battery had been installed. Here are their notes:

"Battery one cell down. Investigate and found draw. Track down draw to panel fuse and found breaker driver seat over hot. Disassemble driver seat and disassemble side command switches. found harness rubbing short on metal part. Repair harness on side panel switches and put harness in correct plastic guidance. Test and no more draw"
Hi Brian, see when your car couldn’t start, did it come up with the “start stop fault. System not ready” error on the dash?
 

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It could either be your new supercap is faulty or the ecu that controls the supercap is (GFA- Aerodynamic ecu)
This ecu controls the built in energizing relay on supercap, also could be faulty starter relay located at fuse box
in engine bay,best way to accurately pin point issue is measuring voltage going to starter solenoid/starter main
when pressing starter button provided issue occurs at time of measure.
 

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Discussion Starter · #8 ·
It could either be your new supercap is faulty or the ecu that controls the supercap is (GFA- Aerodynamic ecu)
This ecu controls the built in energizing relay on supercap, also could be faulty starter relay located at fuse box
in engine bay,best way to accurately pin point issue is measuring voltage going to starter solenoid/starter main
when pressing starter button provided issue occurs at time of measure.
Hello Brian,
If I remove the positive (red) cable from the supercap that goes to the starter motor and connect it directly to the positive terminal of the battery, the car fires up. Basically I bypass the supercap and uses the car battery to start the car. Does this eliminate a faulty starter relay?
Also, does the car needs resetting/ reprogramming after installing new battery and supercap? From previous diagnosis, it seems like the battery is not charging the supercap if the voltages drops in the supercap…..my understanding is that the voltage between the battery and supercap should be a balanced system. The battery should ‘top up’ the dais iron in the event if voltage drop…but I could be wrong…
 

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Yes that would eliminate the starter relay which supplies the starter solenoid,car will need resetting after
installing new battery,supercap has high amps in it ,it should be discharged using a tool dealers have,
after installing new supercap this tool should be used to introduce voltage back in to it,a new supercap will
be completely discharge,and using tool, voltage should be introduced back in to it,voltage in new supercap should
be at least 2.5 V or more for the battery to start recharging it back.
Yes the battery should top up voltage to supercap after every start up or when voltage drops below certain threshold.
Hope this helps you out:)
 

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Discussion Starter · #10 · (Edited)
Yes that would eliminate the starter relay which supplies the starter solenoid,car will need resetting after
installing new battery,supercap has high amps in it ,it should be discharged using a tool dealers have,
after installing new supercap this tool should be used to introduce voltage back in to it,a new supercap will
be completely discharge,and using tool, voltage should be introduced back in to it,voltage in new supercap should
be at least 2.5 V or more for the battery to start recharging it back.
Yes the battery should top up voltage to supercap after every start up or when voltage drops below certain threshold.
Hope this helps you out:)
Thanks Brian. I’m getting the car transported to the garage end of this week and they can fault find again (for the 3rd time). Hopefully it’s a case of the ECU being confused and a resetting will solve the issue rather than getting a new ECU/ GFA. Will keep you all posted.
 

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Signs of the starter motor failing is when the engine crank is slow and takes a long time. Total starter motor failure, you'll either hear nothing at all or just a "click" sound.

When the starter motor is close to failure, you can almost always start the engine when it's cold. However once the starter motor temp increases due to normal engine bay heat, when you turn off the engine and try to start it back up, you'll find the engine crank is slow and takes a long time or sometimes crank once or twice and don't even start at all.

Starter motor failure is quite common as your car approach close to the 10 yr mark. Mine is 2013.
 

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Signs of the starter motor failing is when the engine crank is slow and takes a long time. Total starter motor failure, you'll either hear nothing at all or just a "click" sound.

When the starter motor is close to failure, you can almost always start the engine when it's cold. However once the starter motor temp increases due to normal engine bay heat, when you turn off the engine and try to start it back up, you'll find the engine crank is slow and takes a long time or sometimes crank once or twice and don't even start at all.

Starter motor failure is quite common as your car approach close to the 10 yr mark. Mine is 2013.
I have that issue on my C7 and ordered a shield wrap before buying a new starter.
 
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