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

[Supervinnie40]

Well, another case of good news/bad news.

The bad news is that the wiper motor is not the problem. It gave me the same measurements as the one I got from David. Connecting the new wiper motor still makes the amps go to 0.07. Disconnecting the brown/green wire makes the amps drop to 0.03.

The good news is, while my wiper motor was off, I decided to open it up. 4 black clips around the edge (which come off quite easy) and I could take the top off. Underneath is 1 large gear with some copper on it. When the wipers are down, both brown/green and black touch the same strip of copper. In theory the resistance should be zero, but because of the grease on the copper, there is a small amount of resistance, roughly 5 ohm in my readings.
When the wiper motor turns, the 2 wires mentioned above don't touch the copper anymore and there is no connection at all.

Wires 2 and 3 (the other colored ones) are only connected to the electric motor, and are NOT used inside the "gearbox".

I assume that the BCU is able to determine the position of the wipers, based on brown/green and black making a connection. No connection = wipers not in park. Connection = wipers in park.

However, this still doesn't fully explain the difference between 0.07 and 0.03 when the brown/green is connected or not.
From thinking out loud, I would guess that the BCU reacts to the fact there is a connection between brown/green and black. Reading SD1Too's post where he posted his readings on his car, it seems that 0.07 is not unique (Simon was at 0.09 after several minutes). Perhaps the 0.04 difference in amps is due to the electrical charge that is sent through the brown/green wire? No connection means no electrical current flows, therefore 0.04 amps less drain?? (just thinking out loud now)

I'm starting to wonder if my drain is abnormal or not. Maybe, just maybe, the 0.07 drain is very normal. Not very likely, because it has cost me 2 batteries already. But 0.07 doesn't sound like an extreme amount. And without more readings from other forum members, I'm afraid it's not possible to get a benchmark.

[COLVERT]

That .07 amp drain should be nothing to the size of the battery on our cars.---

[Supervinnie40]

In theory I believe it would be close to 29 days before it doesn't have enough juice to turn the starter motor (with 0.07a).

https://the75andztclub.co.uk/forum/s...2&postcount=85

With 0.03 it would be closer to 67 days, which seems to match some stories I have been reading. I have seen a few mentions of Rovers that where left for 2 to 3 months, and still started.

[Supervinnie40]

Just got a mail from Mister Deej. He owns a V6 and lives not all that far from me. He was also so kind to remove his wiper motor and sent it to me for testing. Unofrtunately that didn't solve anything.

Via Facebook I asked him to:
- unlock the car
- close all doors
- put a weight on the bonnet switch
- put the multi meter in serie
- wait several minutes

Just as with my car, the multimeter started somewhat higher in the beginning, and then dropped to 0.09 and (after a few seconds) to 0.07 where it stayed. We didn't check what it does after at least an hour.

Combined with the readings from Simon's car, I'm inclined to think that 0.07 amp is fairly normal for our cars.
The only thing I can think off now, is the jumping drain I get after well over an hour. Simon did not have those jumping readings.

My car:
After a few minutes: 0.07
After a few minutes (without wiper motor): 0.03
After an hour (unlocked): 0.00/0.07
After an hour (unlocked without wiper motor): 0.00/0.03
After an hour (locked): 0.01/0.08 with excursions to 0.15
After an hour (locked, without wiper motor):

Simon's car:
After a few minutes: 0.09/0.1
After an hour (unlocked): 0.03/0.02 with excursions to 0.09
After an hour (unlocked without wiper motor):
After an hour (locked): 0.03/0.04 with excursions to 0.1
After an hour (locked, without wiper motor): ??/?? with excursions to 0.06

David's car:
After a few minutes: 0.072
After a few minutes (without wiper motor): 0.031
After an hour (unlocked):
After an hour (unlocked without wiper motor):
After an hour (locked):
After an hour (locked, without wiper motor):

[marinabrian]

I checked the quiescent current of my Mk2 1800, and the result was 150mA when the car was first locked, and after 15 minutes dropping to 35mA constantly thereafter with no variation.

I've nothing aftermarket fitted to the car, and an IOVox CD80 radio fitted.


If I leave the car for more than four months standing beginning with a fully charged battery as I have just done, the car still started perfectly.

Disconnecting the wiper motor will always reawaken the BCU from standby if autopark is enabled in factory options.

Sorry I can't be more help, but the test was carried out in real conditions, and I used the current clamp on T4 advanced toolkit for measurements.

Brian

[Supervinnie40]

So, if I interpret correctly:

That's 0.15 a in the beginning, with 0.035 a after 15 minutes?
That is with a locked car, everything closed (as far as the sensors can tell) and measured via T4?

(wonder if that is any different then what we get with a multimeter? As far as I know, TOAF isn't capable of doing this).

[SD1too]

Originally Posted by Supervinnie40

That's 0.15 a in the beginning, with 0.035 a after 15 minutes?

Remember Vinnie that this is a 1.8 litre car with a different ECM to our Siemens type which may draw a higher quiescent current. [It's since been drawn to my attention that Vinnie's car is a 1.8.]

Note also that both your V6 and mine have excursions to a higher current whereas the 1.8 doesn't. I'd still like to see some results from a third V6.

Simon

[Supervinnie40]

I didn't know the MK2 had a different ECM? I was under the impression that all 75's had the same computers, apart from the MK1 and MK2 BCU.

It does serve the question what might be the cause for this difference. You'd think that the standby systems (or the alarm) won't differ on different engines.

Personally I'd like to see a lot more info on other 1.8's haha . I still very much wonder how much my car differs from others.


I would like to repeat from earlier that my car does NOT horn when I lock the car with the bonnet open and nothing on the bonnet switch. As far as I have been reading, this should happen. I haven't tested if the alarm goes off at all (will do that later tonight). But as far as I know the horn should sound when something is left open. This does not happen.
Continueing on that: could the whole problem come from a faulty bonnet switch? Causing a higher drain on the battery because the bonnet switch is faulty?

After I have tested if the alarm works at all, I am probably gonna remove the bonnet switch and clean it, just in case.

[SD1too]

To clarify Vinnie, the 1.8 engine uses a MEMS engine management system and the KV6 uses a Siemens 2000. They might have different quiescent currents which might account for the lower reading on MarinaBrian's car when compared to ours. [It's since been drawn to my attention that Vinnie's car is a 1.8.]

If I lock my car with the bonnet open the alarm sounds, not the horn.

Simon

[Supervinnie40]

That's weird. When I locked my car in the past, with the bonnet open, it would just honk at me. Like somebody hit the horn on the steering wheel. Subtle, but noticable.

Now if I lock the car with the bonnet open, the doors lock but the indicators don't flash at me. There is also no sound.

If I lock the car with the bonnet open, and play with the bonnet switch, the alarm goes off because I see the indicators flashing. But there is no sound....

This is not my video, but this was the same sound my car used to make when locking the car with an open door.
https://www.youtube.com/watch?v=xniYUWXQONw