electrical fault.

[ThatGuyJames77]

hey lovely people of SC.net, so as the title says, I'm experiencing a strange sequence of electrical faults and will give some relevant history to assist in your eye rolling.

My Leon several weeks ago suddenly started screaming at me to stop with a collection of electrical fault indications such as ESC, Tyre pressure, battery, engine management, lights, the works. Upon pulling in and turning the car off for fear of damage, the vehicle successfully restarted but quickly cut out within 1-2 seconds. the faults and screaming of the alarm were present during start and cut out and only stopped upon key removal. This has presented as a slight inconvenience given I work an on call type shift pattern and require a car to reach the works vehicle to attend emergencies.

The next step I took was to use a booster pack over the weekend the fault occurred which allowed the car to start and drive flawlessly. HOWEVER, I ordered a new battery (Start stop) which was fitted after having the wires traced, checked and contacts inspected and drove off fine until a few hundred miles later where today the fault has re-occurred. I read on here just this morning about using the set button on the dash to check battery health and for a two week old battery is showing 0%!!! With the key in the ignition and turned the first click, the locks in the car can be heard to be cycling, the radio is intermittently flashing on and off but the strange bit is, if you're quick when you turn the key, it will start but die after maybe two seconds. I don't have any fault codes at present however I can obtain these later today.

Effectively my question is, any ideas?

Additional info; Leon MK3 5F 2.0TDi 150 64 Plate 70,000 miles, recent clutch, flywheel, slave cylinder and clutch cables fitted after slave cylinder failure, no water damage or corrosion etc the car is well looked after, New battery is definitely start stop and will update this post today with a video showing battery level, warnings and alarms present on ignition and the starting and subsequent stopping of the running of the car.

I really appreciate any insight and or experiences you have had with similar faults, J.


Edit: I've had to upload the video to YT due to the size of it however the faults can be seen with alarms etc, battery percentage shown and the lock cycling can be heard in the background https://youtube.com/shorts/E97MrBSN9gA?feature=share

 

[yorkshire_bob]

Could this be the alternator? I had very similar problems with a previous (non Seat) car and after replacing the alternator it went away.

 

[ThatGuyJames77]

Could this be the alternator? I had very similar problems with a previous (non Seat) car and after replacing the alternator it went away.

I'll take this into consideration as I suppose it is likely to fail being the original one the car had from brand new. Cheers for the input!

 

[adam davies]

hey lovely people of SC.net, so as the title says, I'm experiencing a strange sequence of electrical faults and will give some relevant history to assist in your eye rolling.

My Leon several weeks ago suddenly started screaming at me to stop with a collection of electrical fault indications such as ESC, Tyre pressure, battery, engine management, lights, the works. Upon pulling in and turning the car off for fear of damage, the vehicle successfully restarted but quickly cut out within 1-2 seconds. the faults and screaming of the alarm were present during start and cut out and only stopped upon key removal. This has presented as a slight inconvenience given I work an on call type shift pattern and require a car to reach the works vehicle to attend emergencies.

The next step I took was to use a booster pack over the weekend the fault occurred which allowed the car to start and drive flawlessly. HOWEVER, I ordered a new battery (Start stop) which was fitted after having the wires traced, checked and contacts inspected and drove off fine until a few hundred miles later where today the fault has re-occurred. I read on here just this morning about using the set button on the dash to check battery health and for a two week old battery is showing 0%!!! With the key in the ignition and turned the first click, the locks in the car can be heard to be cycling, the radio is intermittently flashing on and off but the strange bit is, if you're quick when you turn the key, it will start but die after maybe two seconds. I don't have any fault codes at present however I can obtain these later today.

Effectively my question is, any ideas?

Additional info; Leon MK3 5F 2.0TDi 150 64 Plate 70,000 miles, recent clutch, flywheel, slave cylinder and clutch cables fitted after slave cylinder failure, no water damage or corrosion etc the car is well looked after, New battery is definitely start stop and will update this post today with a video showing battery level, warnings and alarms present on ignition and the starting and subsequent stopping of the running of the car.

I really appreciate any insight and or experiences you have had with similar faults, J.


Edit: I've had to upload the video to YT due to the size of it however the faults can be seen with alarms etc, battery percentage shown and the lock cycling can be heard in the background https://youtube.com/shorts/E97MrBSN9gA?feature=share

First question have you scanned it for fault codes, if not do it..
Also like above check voltage when car is off and check voltage when car is running to ensure you're getting over 13.5v

 

[kgp280]

If the alternator is ok then maybe it’s something to do with the Battery Management system.

Was the battery a direct replacement for the one that was removed

Ie AGM or EFB battery tech.
Both are stop/start batteries but have different charging attributes with the AGM being more sensitive to overcharging.

Did the new battery get coded in. This is important if you’re changing battery types, as the BMS needs to know that a new battery has been installed and what tech it is. Otherwise you could damage the new battery.

I recent bought a new battery from TPS, told them my reg number and they then supplied the battery that Seat said was fitted to the car from build. What they supplied was a AGM what I had fitted was a EFB. Battery had never been replaced previous as have owned the car from new.

I therefore had to code the new battery in.

Wondering if after fitting the new battery all worked ok for a few weeks.
But having not coded the new Battery, in the BMS thought the old battery was installed has overcharged it and damaged it.

 

[Walone]

Additional info; Leon MK3 5F 2.0TDi 150 64 Plate 70,000 miles, recent clutch, flywheel, slave cylinder and clutch cables fitted after slave cylinder failure, no water damage or corrosion etc the car is well looked after, New battery is definitely start stop and will update this post today with a video showing battery level, warnings and alarms present on ignition and the starting and subsequent stopping of the running of the car.

I'm wondering, if, when the work mentioned above was done, something was damaged or left disconnected?

 

[ThatGuyJames77]

Hi guys, firstly thank you for all the input and I apologise for the delay in getting back I've had a few lengthy days at work however the issue at hand has been fixed. I had dropped my car into my mate the day I posted this thread and explained to him what was mentioned in this thread, the moment I mentioned battery coding he shot into the vehicle and had it sorted within half an hour. Turns out the battery which I believe was the factory fitted one was EFB and the newly supplied battery was indeed AGM. Unsure of exactly what he did with it but I would assume he had recoded the car to the new battery as he was in with a tablet and the socket for talking to the car. Again, many thanks to you all for your input and if you wish, I can have my mate explain what he did for clarity on the issue. Cheers again guys, J.

 

[kgp280]

Cheers J.
Glad you got it sorted and happy to have helped.

Coding and different battery tech is all well confusing.
Long gone are the days of flat battery out and a new one in.

 

[ThatGuyJames77]

I appear to have spoken too soon, will update when I have the chance, fault has reappeared in the same fashion as before

 

[kgp280]

Oh no that’s no good news.

Wonder if the new AGM battery has been over charged by the BMS and is now damaged. Especially as it wasn’t coded when fitted.

As mentioned in earlier post AGM batteries are sensitive to overcharging. If the BMS thought the old battery was still installed, it would more than likely have overcharged it.

Walone also made a good point did you have these faults prior to all that work being done or after it?

 

[ThatGuyJames77]

It sure is not, that did cross my mind but would it be damaged so quickly? It’s just really odd that it’s worked since Friday night and now it’s causing problems again. So the sequence of events running up to this problem are as follows:

November last year - slave cylinder failure, fixed with a new clutch kit and flywheel since the gearbox had to come out anyway. This was done around the middle of December due to the cost and availability of workshop space (I live rural).

April this year - after a drive of approximately 30 miles just to enjoy some scenery, the car without any warning or loss of power or anything sprung up the warnings which are displayed on the YT short I uploaded. I quickly pulled in and turned the car off thinking maybe the timing system had a problem or something catastrophic had happened. I then utilised the ignition system which then re-displayed the faults and the car refused to start. I left the car to begin a walk home where my mate (the mechanic who has helped me to no end) picked me up and returned to the car. He utilised a booster pack which allowed the car to roar into life no problem, I then drove the car home and the fault re-occurred the next day. Couple of days go by due to my shift pattern (I have live shifts followed by on call) and at random, I decided to check if the car would start, which it did. So a couple of weeks pass until the point of this thread and now here we are.
I can have the battery checked Friday night to see what the numbers are and if need be, I could attempt to source an AGM battery to borrow for a couple of days to see if the fault reoccurs. Now something else I have noticed this last couple of days in the heat we’ve been having, the car is really struggling to move off if the aircon is on (not the AC MAX). Fault codes were read last Friday and displayed approximately 30 faults, all of which were U112300 data bus error value received.

I am genuinely stumped, if I could shock it back to life with a defib, please believe me I would

Edit: unsure as to why the forum is showing me as being in the US, this is false I am Scotland Based.

 

[andylong]

AGM batteries have the highest end of charge voltage of flooded, efb and AGM batteries.
It also has the lowest internal resistance allowing higher charge and discharge currents.
Conditioning from chargers should be avoided on both efb and AGM as the voltage will be too high and they don't need it.
Can you overcharge an AGM battery in a car which thinks it's got an efb battery? I don't see how, since efb batteries will have a lower end of charge voltage which in essence means the AGM battery will never see the end of charge voltage it requires to fill as the current into it will reduce before that happens.
If your car charging circuit is faulty then sure it could then happen.
There's nothing that happens to an efb battery whilst charging that would trouble an AGM. The reverse is not true.

 

[kgp280]

Fair point Andy. Tks for the info.