Hi all,

 

I  fitted a new battery about 1yr ago and all seemed fine until one day both electric windows stopped working.

if I pulled the fuse out and refitted it,  they  would work again once or twice before stopping working again.

I checked the battery to find it was only 50% charged.

i have to add that i have been using a tyre inflator every other 3rd day as the car is prone to unknown slow punctures.

i assumed that this would be dropping the battery voltage down even though i always have the engine running when using it.

i charged the battery and connected the tester to find overnight it would drop to 75% charged.

the only thing that has changed since fitting the battery is that i had to fit a new door harness & i fitted a new head unit.

so i pulled the fuses for the electric windows & radio, now i don't seem to have any drain.

how can i test which circuit is possibly at fault?

i have a little electrical knowledge.

 

thanks

 

craig

 

Do you have the radio wired up correctly, it is usually necessary to reverse the red and yellow wires since one is permanently live and the other is switched live, your radio would still work fine but it would lose its memory every time you switched the car off and it would drain the battery.

Pulling fuses is the wrong way to diagnose battery drain on CAN-bus based cars. It can cause modules to stay awake and use more power than normal.

 

Instead, you need to override the door/bonnet switches so the car thinks everything is shut, disable the internal alarm sensors and then lock it. Wait a while for everything to turn off and measure the voltage drop across each fuse. Using a conversion chart, you can then figure out which circuit is pulling the extra current.

 

There is a useful pdf here: https://wiki.bentleypublishers.com/download/attachments/83329026/vw.current.draw.tb.pdf?api=v2

 

And this appears to be a video of the same methodology:

 

Hi Craig, Hope you get an answer or some help soon but I have heard of aftermarket audio equipment doing funny things like this to others, although I am usually in the MK2 forum. You might find this to be the issue but you could possibly have inadvertently shorted out the harness somehow so it keeps draining the power. I find this a little unlikely though but possible. If the windows and head unit share the same fuse, have you thought of disconnecting the head unit for a while and seeing if the problem persists? If it does, then its most likely NOT that. 

 

I would also not rule out a duff battery, despite it being quite recent. Was it "New" and also, of the correct type for the vehicle? You may well have purchased a used one that seems ok but is weak or drained it too much by having too small  a bit for the consumption of the car, particularly regarding the quite frequent use of the tyre inflator! Have you left any over battery-draining items switched on? (Rear screen heater, mirror heaters, foglight, etc).

 

I have also heard of glovebox lights that fail to go off when you close the glovebox so the bulb is on 24/7. Easy to spot, pop your mobile on to video, assuming you have a smartphone, slip it into the glovebox, facing the light, close the glovebox. Open and close it a few times then view the footage to see the light going on and off (Or not)!

 

This may not be relevant if the glovebox doesn't share the same fuse but its worth noting. (Tailgate lights can even do the same thing but are easier still. Just remove the parcel shelf and close the tailgate. Look in through the window). 

thanks for replies.

yes i reversed the wires to radio, it holds its memory.

how do i override switches and disable sensors?

if i lock it, i obviously will have to unlock it again will this not get the alarm awake?

 

sorry if i am missing the point, its been a long day at work.

battery was brand new from Halfords.

having the battery tester connected to battery with engine running, i can have lights on full, heater on full & heated rear screen on and it looks like battery is getting charged ok.

49 minutes ago, craigsvrs said:

I checked the battery to find it was only 50% charged.

Well, do you get the charge light showing when you switch the ignition on and going out when the engine fires?

Hi Ken,

 

yes i do.

car seems normal, its only been highlighted because i am using the tyre inflator so much.

sort of got used to the windows not working.

battery looks to be holding its charge with those 2 fuses out?

11 minutes ago, craigsvrs said:

car seems normal, its only been highlighted because i am using the tyre inflator so much.

Well, I'm now pretty sure it.s not the alternator control wires (unfortunate because it was an easy check and fix if it had been).

i was going to try putting 1 of the 2 fuses back in and see what happens over the next couple of days.

just on a slight sidenote, would the windows not operate if there was not enough power in the battery do you know?

1 minute ago, craigsvrs said:

would the windows not operate if there was not enough power in the battery do you know?

I don't know either way, but when my alternator clutch stuck open the car turned off the radio and interior fan to make the remaining battery last longer, so maybe.

As I have posted quite a few times before,a DC Current clamp meter  is the correct way to find  where the current is being drained. It needs to have two scales one being 4 amps DC  max,the other scale about 80 amps DC max. Nothing needs to be disconnected,it just clamps around the red battery cable where it is connected to the battery 12v positive terminal. Have it on the highest scale to start with,and  dont start the car,it will overload the clamp meter.Starter motors take about 300 to 400 amps. If you start the car you can then put the clamp meter around  the cable,meter will show if the battery is being charged,or any drain. You will need to leave the meter connected ,and allow 10 minutes for the alarm,widows,etc to go to sleep. Normal lowest current drain is  up to about 150 mA ( 0.0015 Amps) You can put the meter on any cable to trace the fault.

DC Current reading clamp meters are not cheap,about £30 to £100,but they are also very useful for checking house wiring when set to the AC Current range.

Completely remove the radio for a few days, and see what happens. 

6 minutes ago, AndyPandy said:

If you start the car you can then put the clamp meter around  the cable,meter will show if the battery is being charged,or any drain. You will need to leave the meter connected ,and allow 10 minutes for the alarm,widows,etc to go to sleep. Normal lowest current drain is  up to about 150 mA ( 0.0015 Amps) You can put the meter on any cable to trace the fault.

DC Current reading clamp meters are not cheap,about £30 to £100,but they are also very useful for checking house wiring when set to the AC Current range.

I think  that you have made a typo and meant to say 15 milliamperes, in which case I concur with what you said, I did not know that a DC clamp meter existed let alone one that could measure such a low current, I will have to investigate.

 

To the OP. Your problem is almost certainly the radio keeping the Canbus active, you will need to fit and code a canbus gateway controller with a later revision number, its well documented.

 

Been there done that and got the new battery under one year old that is now more knackered than the 7 year old inferior spec one that it replaced that has not even been charged for 3 months 😞

 

As an aside, having resolved that my quiescent current was still too high until Wino I think it was alerted me to the drain from my towbar electric module, its down to a respectable minimum now but the damage is done to the battery, I see that yours is a new one, - take good care of it!

You can indeed get DC current clamp meters! If its of any interest this video gives a very good explanation of how they work and some tips for measuring low currents (which arent practical for the main battery lead), its worth viewing just to get your ear in to the I think Indian gentlemans pronunciation, he gives a very concise  informative tutorial without all the usual BS that comes on many Youtube videos

16 minutes ago, J.R. said:

I did not know that a DC clamp meter existed let alone one that could measure such a low current, I will have to investigate.

 

You are basically correct, DC clamp meters use the hall effect rather than AC induction but they are much too expensive to be a DIY tool and they simply won't reliably measure such small quiescent currents unless you buy a REALLY expensive one and have it calibrated regularly.

I've made this point before and faced substantial argument so I've given up trying.

Well I am glad that you continue to reinforce the point, you have saved me from investing £30 or so on a chocolate teapot when £7 or so would have bought me an AC clamp meter with current probes for measuring DC.

 

Many of the Ebay listings that said they measured DC current had test probes.

 

In fact I have lasted all these years measuring both AC and DC currents without ever having a clamp meter, I can see for mains voltages one would definitely be safer.

 

 

AC and DC current clamps are handy to have for some tasks, though I think £30>£100 is not going to give you a device that can handle something like down to 150 milli amps accurately - certainly not one that can fit over some of these heavy battery leads, I think that all you will witness is what I initially did, lots of changing figures/values that are worthless and do not relate in any way to what an in-line current meter will show.

 

I chased my tail trying to find where current leakage was on a late 2009 Ibiza and my way of checking current, ie present battery drain was by using a good quality DVM and fitting a crock clip to one side of the meter and connecting that to the body earth at the battery, then connected a long probe lead down onto the centre of the battery post, then slacken off and lift up the battery earth lead over the long probe lead.

 

One thing that I was satisfied that I had worked out is, with the ignition off and the doors closed (interior lights out), by keeping the bonnet open, the usual systems will still go to sleep as intended - and removing the battery earth while allowing the earth to be routed through the current side of a good DVM/DMM did not cause any systems to waken up.

 

Your current drain seems to be quite high and hopefully not as tricky as mine was to track down as my problem ended up just being a coding issue with the car's power distribution controller, I really did know that this was the root cause but VW Group experts would not entertain that theory quickly, it took a second VW Group dealer to listen to me after checking that car for current drain and any other faults, SEAT UK provided a BCM S/W patch that solved that issue which was meant to be known about by all marques.

Always ask to speak to a master tech Mo, they're the only ones who know anything, service managers can only find ordinary techs arses with their hands because they're already bending over.

I would be very suspect of a cheap DC ammeter that can measure 15mA on a 4 amp range. I've got £500 worth of Fluke 771 clip on that will supposed measure 4-20mA instrument loops but even that is a bit hit and miss.

 

The only way to do it properly is to measure the volt drop across each fuse and consult the TSB

 

https://wiki.bentleypublishers.com/download/attachments/83329026/vw.current.draw.tb.pdf?api=v2

11 minutes ago, SuperbTWM said:

I would be very suspect of a cheap DC ammeter that can measure 15mA on a 4 amp range. I've got £500 worth of Fluke 771 clip on that will supposed measure 4-20mA instrument loops but even that is a bit hit and miss.

 

The only way to do it properly is to measure the volt drop across each fuse and consult the TSB

 

https://wiki.bentleypublishers.com/download/attachments/83329026/vw.current.draw.tb.pdf?api=v2

 

As good a reason as any to make sure that the car fuses all have both sides of all the fuses exposed, quite a few aftermarket fuses have not got exposed ends.  I seem to prefer HEME current clamps, what you have been brought up with at work I suppose.

thanks for all the input.

so it looks like I either need to get a newer gateway controller or put the standard radio back in?

how do I know where to start with getting a new controller? 

Will the head unit maker not supply patches or am I barking up the wrong tree?

is this what I need?

Barking up the wrong tree, we eliminated the radio earlier when you confirmed that you'd reversed the wires.

I think your problem lies in the loom or the drivers window motor.

 

The CAN gateway won't be at fault.

Edited 28 January, 20206 yr by sepulchrave

Will so!

 

Reversing the wires will not do anything if they are both permanent live feeds and the radio is shut down by the canbus, this is certainly the case on later vehicles like mine, if its not the case on the OP's then I will wind my neck in but what he describes sounds identical to what I went through and many others before and after me after fitting an aftermarket head unit.

 

Editted, reversing the wires and the radio still retaining its memory would indicate that they are both permanent live 12v feeds & hence the drain will most likely be the canbus not shutting down, mine was resolved by fitting a later revision gateway.

Edited 28 January, 20206 yr by J.R.

How does this CAN thing fit in with the failed windows and the changed door loom?

Why doesn't the OP get these slow punctures repaired?

Why not just disconnect the radio, put the fuses back in and see if the problem continues?