Mk7 Stop/Start System - Issues and Questions

**flagger** · 30-06-2014, 09:01 AM

Originally Posted by Transporter

I don't drive the car with the stop start technology, but when you leave the A/C switched "ON" shouldn't that automatically disable SS feature.

Start/Stop works fine when AC is turned on. When the SS kicks in, the AC compressor will turn off, but the cabin fans will still run to circulate the air. Once the car starts up again, the AC compressor will start up again.

I too have a base 90TSI DSG, and only once has the SS system shown an error and failed to turn off the engine. Not sure why, it just showed an error occurred with the SS system on the LCD screen and in the SS section of the info unit. The next day it started working again, and has been fine for several thousand km's. Never has the engine failed to start up again once the engine has stopped in a SS situation.

As above, the alternator should always be keeping the battery topped up while you drive, provided you are not powering crazy things like a 10000W RMS stereo system.

**Midfielder** · 17-07-2014, 11:58 AM

Thnx so much jjr for your post. I am experiencing almost exactly the same problem. My Mk7 90tsi DSG was purchases in Feb an I had Start-stop problems from the beginning. On first memorable occasion I was on slight slope an car rolled back when car wouldn't restart. On another occasion my wife was driving and car wouldn't restart at roundabout. She had to manually restart. I also have experienced embarrassment of failure to restart in busy traffic annoying drivers behind. At first I thought it must be something I'm doing but it's not. Basically I would turn off the stop start with each drive and car otherwise works OK. I haven't experienced problem if the Auto hold is disabled and Stop start ON but rarely drive in this setting. Like you I usually experience the problem after extended driving (eg 20 mins into trip; ?? Worse with air conditioner working hard) and when I took it to VW mechanics last week they didn't reproduce (they appeared to drive for 15km on Odo) and couldn't find anything wrong. I'm really concerned about this problem and really don't know what to do - mechanic said they will email VW headquarters to see if others reporting but seems unaware of this as a common problem. I've wondered about the synthetic oil/mineral oils recall issue experienced in hot climates in 2013 but this apparently doesn't apply to my car. Would've to hear more if u find anything out

**DV52** · 17-07-2014, 04:59 PM

Originally Posted by flagger

Start/Stop works fine when AC is turned on. When the SS kicks in, the AC compressor will turn off, but the cabin fans will still run to circulate the air. Once the car starts up again, the AC compressor will start up again.

flagger: I agree entirely with what you have said, but I think that it's the other way round. My observations of the way SS works is that once the AC compressor is operating (i.e. the set cabin temperature is not yet reached), SS will not turn-off. In a sense, SS is the "slave" of other functions (like AC compressor, seatbelt, steering wheel angle etc), rather than the "master" function.

But as far as kesh's problem is concerned, I agree that studying the discover media screen (watching the SS reports) is a good way to get the required info to resolve the issue. Transporter's suggestion of video-ing the screen shots when the fault occurrs is also worth considering (I think).

**Midfielder** · 17-07-2014, 09:02 PM

Folks, I've managed to video the stop start failure - I'm taking video to mechanic tomorrow and will try to reproduce problem while mechanic with me - I'm going to a different dealership who say they've seen similar problems

**flagger** · 18-07-2014, 09:39 AM

Originally Posted by DV52

flagger: I agree entirely with what you have said, but I think that it's the other way round. My observations of the way SS works is that once the AC compressor is operating (i.e. the set cabin temperature is not yet reached), SS will not turn-off. In a sense, SS is the "slave" of other functions (like AC compressor, seatbelt, steering wheel angle etc), rather than the "master" function.

I have the basic aircon setup in my 90tsi, not climate control. I would have assumed that the SS programming would have been the same regardless of the aircon setup, but there you go. No wonder there is some confusion between car owners in regards to how SS works.

**Kesh** · 18-07-2014, 09:29 PM

So I was thinking recently about the use of stop start in my mk7 or indeed any car. While it's obvious that it will save quite a bit of fuel during long stops, there's no arguing that those short bursts of stops put a lot of strain on both the starter and the battery. One would think that the battery and starter would need to be replaced sooner because of the extra wear. My question is, would you be better off just turning start stop off in favour of using more fuel but saving the battery and motor?

**team_v** · 18-07-2014, 10:42 PM

The battery required for the stop start technology is an EFB (Enhanced flooded battery) and is significantly more expensive than the standard AGM battery.
Unless you are saving $50 in fuel each year due to stop start it wont be worth it.

**Midfielder** · 19-07-2014, 02:19 PM

Took Golf into dealership yesterday armed with video - this was reviewed by fireman who downloaded onto his computer. This really helped the interaction and he said he didn't need to drive the car. Says he emailed Sydney office HQ and they immediately told him to do a 'software update' and he was hopeful this would fix it. Prior to that he had all sorts of theories as to what the problem might be. I've since driven car perhaps 2 hrs in total without a problem but its early days. I'll keep u up to date

**lambertia** · 19-07-2014, 11:26 PM

Yes absolutely it will save money.

It is true that cars with stop/start have more expensive batteries. I think AGM if the car has blue motion as this includes charging during brake recovery. If for whatever reason you need to replace the battery in your car you're supposed to put the same battery type in. So in terms of start/stop the cost of the battery is not relevant. You're stuck with it because you bought the car.

I think that the only way stop/start could cause you to not save money is if in the life of the ownership of your car it causes you to replace the battery more often that you otherwise would. For example twice in five years rather than one. I'm no expert but I assume that because the battery is designed for stop/start that this is unlikely to be the case.

As covered elsewhere the starter/engine/battery is designed for all of this. Don't use it because you just don't like it but don't turn it off because you think it won't save money.