MY15 Polo 6c 81tsi Bluemotion Issue

[cam_cap]

Hi Guys,

I am having an issue with the Bluemotion when the car starts after idle. All lights including headlights, DRL'S & all interior instrument lighting turns off for 2-5 seconds when pressing the clutch to take off.

I have taken it back to the dealership twice now and they can't place the fault.

It started off doing it very irregularly but now does it around 1 in 5 times of stopping at traffic lights.

Just wondering if anyone else has had this issue.

Cheers,
Cam.

CamCap

Black MY15 Polo 81tsi Comfortline - Manual
w Sports & Comfort Packages

[HenryJr]

Wonder if its a battery/alternator issue

[staz88]

Dodgy earth connection?

[LukePolo]

Firstly, I would check that all the battery connection nuts are on nice and snug

Secondly, evaluate if anything is discharging your Battery such as a dash cam or other Auxilary accessory while the car is in the Bluemotion stage and when it's turned off with the key out.

Thirdly, If none of the above is working, I found that those eBay voltage checkers via the 12v plug works quite well and was very very close to the voltage metre connected directly to my charging system. Note down the drop when the car is starting. Generally all the electrics cut off if there is a large drop in voltage upon starter motor crank.

Basically assess whether your car thinks it might have enough charge but actually doesn't.

Question though... Have you ever had a flat battery?

[DV52]

As OPs have already stated, the condition of the battery is worth checking, but my understanding is that the Start/Stop system that VW uses doesn't directly use raw battery voltage.

Instead, and from what I have read, many of the decisions that are made by VW models (including the decision to activate the SS facility on the new Polo) uses what VW calls "system voltage". System voltage is a calculation that's performed by the car based on a bunch of stuff including the previous charging/discharging history of the battery, the temperature of the battery and the characteristics of the alternator. Most of the variables for the calculation of system voltage comes from the battery monitor control module that physically sits next to the battery negative terminal (see picture below).
So, the component that's causing your wierd behaviour may well be more complex than simply battery voltage (I think)
Cheer
Don
PS: the existence of the battery monitor on the negative terminal is the reason why you should never connect the negative terminal of a jump-battery directly to the car's battery. If this is done, the battery monitor is by-passed and the charging current into the car's battery is never recorded- causing the calculation of system voltage to be incorrect

[cam_cap]

Firstly, I would check that all the battery connection nuts are on nice and snug

Secondly, evaluate if anything is discharging your Battery such as a dash cam or other Auxilary accessory while the car is in the Bluemotion stage and when it's turned off with the key out.

Thirdly, If none of the above is working, I found that those eBay voltage checkers via the 12v plug works quite well and was very very close to the voltage metre connected directly to my charging system. Note down the drop when the car is starting. Generally all the electrics cut off if there is a large drop in voltage upon starter motor crank.

Basically assess whether your car thinks it might have enough charge but actually doesn't.

Question though... Have you ever had a flat battery?

Hi Luke,

Thanks for your comment!

I don't have a dash cam or any equipment plugged in.
I haven't had a flat battery either.

CamCap

Black MY15 Polo 81tsi Comfortline - Manual
w Sports & Comfort Packages

[Guest001]

As OPs have already stated, the condition of the battery is worth checking, but my understanding is that the Start/Stop system that VW uses doesn't directly use raw battery voltage.

Instead, and from what I have read, many of the decisions that are made by VW models (including the decision to activate the SS facility on the new Polo) uses what VW calls "system voltage". System voltage is a calculation that's performed by the car based on a bunch of stuff including the previous charging/discharging history of the battery, the temperature of the battery and the characteristics of the alternator. Most of the variables for the calculation of system voltage comes from the battery monitor control module that physically sits next to the battery negative terminal (see picture below).
So, the component that's causing your wierd behaviour may well be more complex than simply battery voltage (I think)
Cheer
Don
PS: the existence of the battery monitor on the negative terminal is the reason why you should never connect the negative terminal of a jump-battery directly to the car's battery. If this is done, the battery monitor is by-passed and the charging current into the car's battery is never recorded- causing the calculation of system voltage to be incorrect

A So if you are jumpstarting a car with that where do you put the neg clamp.

B If you are using a VW to jump another car how should you do it. I had to use the Polo to start the Passat after not using it for 9 weeks.

Just did the hook them together leave donor running for 10 mins and then start the flat one. Hasnt seemed to harm it. (hopefully)

[DV52]

A So if you are jumpstarting a car with that where do you put the neg clamp.

B If you are using a VW to jump another car how should you do it. I had to use the Polo to start the Passat after not using it for 9 weeks.

Just did the hook them together leave donor running for 10 mins and then start the flat one. Hasnt seemed to harm it. (hopefully)

Hillbilly: hello again. Incorrectly connecting two batteries in a jump-start configuration won't "harm" either battery and in the short term neither car will probably see any affect at all. But, as I said in my previous post, bypassing the battery monitor means that the system voltage calculation (which uses the battery's charge/discharge history) will not be correct. I suspect that the critical impact to the car in this instance will be when the incorrect system voltage calculation causes a control module to make the wrong decision (or, said another way, causes a control module to not make the correct decision - which can be very different).

If either, or both jump-cars are built on VW's MQB platform and if they have Bluemotion, they will have a battery monitor as per my picture above. I've not pulled-apart a VW battery monitor, but I suspect that it has some type of rudimentary DC current transformer as a sensor whereby the magnetic field that results from electrical current flowing into/out-of the negative battery lead is recorded and continuously updated in a table somewhere in the car's central memory (probably in the instrument panel). The data in this table is a pivotal input to the calculation of the car's prevailing system voltage and the number in the table doubtless determines the car's understanding of how much charge remains in the battery to do stuff like operate Start Stop activities.

Therefore, when dealing with bluemotion cars, It's very-important to include the battery monitor into the "electrical configuration of the jump circuit" to ensure the veracity of the car's understanding of the real condition of the battery.

As for your specific questions - I've listed below the three possible scenarios when jump-starting VW's MQB platform vehicles (hopefully, as your read each scenario, you can visualise how the placement of the negative battery lead connection includes the battery monitor into the jump circuit):

1. One car has blue motion- the other doesn't - The negative lead of the car that doesn't have bluemotion should be connected to the negative battery terminal and the other end of the negative lead should be connected to a naked bolt on the body/engine of the car that has bluemotion. The positive battery lead should be directly connected to positive terminals on both batteries
2. Both the host and the guest cars have bluemotion - The negative battery lead should be connected to a naked bolt on the body/engine of both cars. The positive battery lead should be directly connected to positive terminals on both batteries.
3. Both cars don't have bluemotion -The old-fashion way of hooking-up the batteries will suffice. That is directly connect the negative lead to the negative terminal on each battery and the positive lead to the positive terminal on each battery

The battery connections should be made in the order written

Hope that I haven't confused anyone - my apology if I have done so
Cheers
Don

EDIT: Here's a diagrammatic view of what I'm trying to say (badly) above - Note how the battery monitor is in-circuit with the correct placement of the negative jump lead and the battery monitor is by-passed (i.e. out-of-circuit) with the incorrect placement of the lead.