Battery drain... is it the BCU or LSM?

[Supervinnie40]

Yet another weird thing discovered.

If I disconnect the battery, then disconnect the wiper motor and then reconnect the battery... the interior lights stay on and the amps go up to 1.438.
After 10 minutes, lights are still on.

Opened and closed all doors and waited 10 minutes: still on.
Locking and unlocking the car: lights remain on, even when locked.

Reconnecting the wiper motor immediately makes the amps drop down to 0.5, and after a few minutes the lights go out and the amps drop down to 0.07.
If I disconnect the wiper motor at that moment, the amps drop down to 0.03 and the lights don't come on.

So, making the BCU boot without the wiper motors makes the whole go funky?

[sewerman]

Could be a motor winding in the wipers starting to fail and giving a very low amp arc?


Sent from my SM-G977B using Tapatalk

[Supervinnie40]

I wouldn't know to be honest. As far as I can see, the power isn't going to the motor itself. If I unplug just the motor (2 wires), nothing happens. There seems to be some kind of gearcase underneath is (black thing) that probably has some electronics in it. I'm inclined to think something's wrong in there, but it is completely unclear why or how.

Seeing as Simon said it isn't the motor, it could possibly be something that is connected to it?

I've already thought about things like a bad earth (which should affect other systems as well?)
Maybe a broken wire? (But then it shouldn't work)
A faulty switch (but then something shouldn't work)
A fault within the BCU that controls the wipers? (not sure how to test?)

Only know I've got a MK2 BCU in a MK1 car, which came up a few times in the past. But if that really was the problem, shouldn't other's have similar problems?

[SD1too]

Originally Posted by sewerman

Could be a motor winding in the wipers starting to fail ...

I considered a current draw through the motor too Scott but Vinnie measured 0v on both the slow and fast speed supplies.

Originally Posted by Supervinnie40

Only know I've got a MK2 BCU in a MK1 car ...

Do you mean the lowline (cream coloured) and highline (black) versions?

The BCU controls both the wipers and interior lights. You've reported problems with both.

Simon

[Supervinnie40]

I'm not 100% sure what you mean with cream coloured? I guess I haven't seen enough of these units to know that detail.

What I do know:
I used to have a MK1 in my MK1 (surprise surprise ). But I wanted to open the boot via the key, and I preferred a few other options the MK2 BCU has, that the MK1 BCU doesn't offer. A few years ago I bought one via eBay and drove to the UK and had it installed. I'm not 100% sure anymore who did it. He was a very friendly gent of slightly older age who lived somewhere in the area around London (if I remember correctly). I know he's a bit of a T4-guru but forgot his name .

He installed the MK2 BCU and programmed it into the car. He also activated that the headlights stay on when I get out of the car, and auto-turn off after a few seconds. Weirdly enough, the BCU wouldn't save the same settings on the rear lights. It would throw up errors. When I left, everything was working fine and all the new options where working very nice.

I know it is a black box, which looked identical to the old one, but with a different number on it. I think the number is YWC001521 ?? (I have 1 bad photo with this number)
I don't remember having any problems with it, and the first problems with the battery started a lot later (first time was 2 years ago. The second time was 7 months ago en the third time was 2 months ago).

I've never had problems with the interior lights, until I disconnected the wiper motors. At that moment the lights wouldn't go off anymore. Even locking the car didn't make the lights go off. My uneducated geuss would be that the BCU starts getting funky when the wiper motors are disconnected. Something causes the whole system to act weird, and the interior lights could perhaps be a symptom of the system going haywire because it can't find the wiper motor.

To be honest, it would be helpful if somebody with a MK2 BCU could try to unlockt the car, then disconnect the battery, then disconnect the wiper motor and then reconnect the battery. See if the interior lights act normal or not.

The wipers themselves haven't really given my any problems. They work perfectly fine, the interval works and it goes down to park-poistion properly. But it is true that disconnecting the system makes the amps drop to a normal level. Which seriously confuses me.

My questions:
- Would replacing the BCU with another unit (Newer? Older?) fix the problem?
- Could somebody with a MK2 BCU be able to test what happens with disconnected wiper motor?
- If I need to replace the BCU, would I be able to program this with TOAF?

[Supervinnie40]

After scrolling through the forum, I think the BCU was changed somewhere in the summer of 2015, perhaps 2016. The nice fellow could've been Phil-T4 if he lives in Milton Keynes?

I do have a photo (I hope he doesn't mind me placing it :O ). And the date on the photo is 2015-07-25 (funnily enough, that's my birthday.. You'd think I'd remember that).
https://scontent-amt2-1.xx.fbcdn.net...87&oe=5F02067C

I got my first IPK with LCD screen installed and we swapped the BCU from MK1 to MK2.

Bit of a report of that day:
https://the75andztclub.co.uk/forum/s...d.php?t=222145

[SD1too]

Let's hope that Phil sees this thread and throws some light upon it. Are you sure that your car didn't originally have the lowline BCU (case the colour of cream or warm white) and no message centre in the original instrument pack?

Simon

[Supervinnie40]

My car didn't used to have the LCD screen, which was reason to change the IPK. I don't remember what color the previous BCU was, but I'll have a look in the attic. I save most of the replaced stuff.

To add on top of the information: I wanted to test the amps drain when the car is locked. So I plugged everything back in, and I locked the car. But the lights remained on. I didn't understand why, because the wiper motor is reconnected. After a few minutes I realized the passenger rear door was not closed properly. However, the horn didn't make a sound (which it used to do in the past).
This could be due to the bad battery (just guessing), but it never made any sound to warn me that a door was open. Also the locks all worked, all doors where locked even though 1 door was open.
I do know that it worked before, I have had a few times that I locked the car after washing, and I didn't close the bonnet. It always honked at me to let me know something was still open.

[SD1too]

So is the interior lights issue no longer relevant?
Are we back to understanding the 0.7 amps battery drain?

Simon

[Supervinnie40]

Edit:

Apologies for the misinformation. My girlfriend just came back inside to tell me that the clamp on the bonnet switch has come off. I didn't notice that.
When I put it back, and put the multi meter back on, without the wiper motor being connected, the car acted normal. In the way that the lights remain off, and after opening/closing a door, the lights do go off after a few seconds.
If I wait a few minutes, the amps go down to 0.03 and remain there.
I put the battery back on the charger, it was due to be charged... again...

In either case, the horn won't sound when I lock the car with a door open. But the locks will still lock and the lights flash twice.

By the way, the car has been locked for about an hour now. The amps jump up and down between 0.08 and 0.01. This seems the happend randomly. Sometimes it goes up to 0.04 or 0.06, and other times it goes up to 0.08 before it drops to 0.01 again. It goes fairly quick. Going up to 0.08 and back to 0.01 takes about 1.5 or 2 seconds.
When the battery if full again, I will retry this test but with the wiper motor disconnected and see if the amps still jump up and down.

Personally, I'm still not sure whether it is the BCU acting up, or if the wiper motor is causing the drain. However, I do feel relatively confident that we are on the right track with these 2. Nothing else in the car seems to affect the drain as much as these 2. (mainly refering to Fuse 5 in the interior).

I did look, and I couldn't find the old BCU. I don't properly recall it being black or grey .
I looked at Google ( https://www.google.com/search?q=rove...=1920&bih=1067 ) and I see the different versions. Although I'm not 100% sure, I do not remember the old one being so lightly colored. The fact that both boxes have totally different colors would be something that would've been remarkable enough for me to remember. I'm sorry for the hazy information, but I'd say I'm 75% sure it was a black BCU.


****Original message****
Yes and no.... lol, it's never easy now is it?

If I:
- disconnect the battery
- disconnect the wiper motor
- reconnect the battery (with the multimeter in series)
the lights remain on, and they won't go off. Not even after 20 minutes. Also, locking the car doesn't change this either. The amps are fairly high and won't go down (probably due to the lights being on)

But, if I:
- disconnect the battery
- leave the wiper motor connected
- reconnect the battery with the multimeter in series
The car acts normal. The lights only go on if I open a door, and go out after several seconds. The amps go up at first (0.38 if I don't open a door), but go down after a few minutes to 0.07.