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

[MarkS]

Originally Posted by Supervinnie40

Actually, I think I can hot-switch. Before the photo, the multimeter was set to 10a. I only turned the dial to 200ma. I didn't switch over the probes. It still gave me the same value. So it seems to work.

For what it is worth, one of the consequences of using the 10A connector with the switch in the 200mA position, is that the meter puts the decimal point in the WRONG position: A reading of 00.7 (in the photo) is actually 0.07A, assuming that there are not other issues to do with misusing the meter, which there probable ARE.

You MUST use the meter in the 10A switch position.

Or be prepared to be confused, and lead everybody here up a false path, by making mistakes.

Sorry if I appear to labour the point.

[MarkS]

Originally Posted by 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.

I apologize for possibly interrupting your train of thought, but with a 3 1/2 digit multimeter (such as the Skytronics 600.006 shown in the photo) set to the 10A range, it is IMPOSSIBLE to get a true current reading of 1.438 amps.

If the current were 1.438 amps a 3 1/2 digit meter would display 1.43 amps or 01.43 amps.

There is something WRONG here.

[Supervinnie40]

Thanks for the advice MarkS. Nothing wrong by trying to prevent things from getting even more unclear.

I have done most readings with the switch in to 10A position. And because I found it easier to read without having to calculate from 00.7 to 0.07, I've been using the 10A position for the majority of readings I've done.
When in doubt I also switch back and forth between 200ma and 10A, just to see if there is any difference. Call it a "double check".

[Supervinnie40]

Originally Posted by MarkS

I apologize for possibly interrupting your train of thought, but with a 3 1/2 digit multimeter (such as the Skytronics 600.006 shown in the photo) set to the 10A range, it is IMPOSSIBLE to get a true current reading of 1.438 amps.

If the current were 1.438 amps the meter would display 1.43 amps or 01.43 amps.

There is something WRONG here.

I didn't take a picture of it. So I'm not 100% sure why I wrote this down. I also have it on my notepad that I keep close when doing readings. I'll try and replicate the situation and double check.

Nonetheless, it doesn't really matter that much. The situation in which this happened was due to me not realizing that the clamp on the bonnet switch come off. If I had noticed that, this situation wouldn't have occured.

[Supervinnie40]

Hmmm, that was a bit odd.

Due to MarkS comment on the 3 numbers behind the comma, I tried to recreate the situation. Take of the bonnet clamp, reconnect the wiper motor and reconnect the multimeter with the battery and the lead. In the second (comparison) test I would do the same, except disconnect the wiper motor.
But, while I was waiting for the amps to go down (wondering if it would), the wipers suddenly moved an inch. I didn't press anything, they just moved. So I aborted my test.

Thinking I did something wrong, I took off the lead, and put the clamp back on the bonnet switch and made sure everything was back as it should be.
Then I reconnected the multi meter and waited for the amps to go down again. After a minute or 2, the wipers moved one rotation. Then they stopped.
The amps did go down, but only to 0.07. Pulling the plug on the wiper motor still made it drop further to 0.03.

So, everything is back to normal. Nonetheless, I was very surprised that the wipers moved an inch the first time, and did a full sweep the second time. Spooky...

[MarkS]

Originally Posted by Supervinnie40

Hmmm, that was a bit odd.

Due to MarkS comment on the 3 numbers behind the comma, I tried to recreate the situation. Take of the bonnet clamp, reconnect the wiper motor and reconnect the multimeter with the battery and the lead. In the second (comparison) test I would do the same, except disconnect the wiper motor.
But, while I was waiting for the amps to go down (wondering if it would), the wipers suddenly moved an inch. I didn't press anything, they just moved. So I aborted my test.

Thinking I did something wrong, I took off the lead, and put the clamp back on the bonnet switch and made sure everything was back as it should be.
Then I reconnected the multi meter and waited for the amps to go down again. After a minute or 2, the wipers moved one rotation. Then they stopped.
The amps did go down, but only to 0.07. Pulling the plug on the wiper motor still made it drop further to 0.03.

So, everything is back to normal. Nonetheless, I was very surprised that the wipers moved an inch the first time, and did a full sweep the second time. Spooky...

It is not unexpected.

The R75, like most modern cars, has self parking wipers. If the ignition switch is switched off, before the wipers have parked, the power is kept on to the wipers, until the wipers are parked.
This is achieved by having a contact in the wiper motor gearbox, that closes when the wipers are not FULLY parked. This is pin 1, the thin brown wire. This signal is fed INTO the BCU, which then commands the wiper relays on.

The fact that pin 1 was giving an unsteady voltage of 0.4-0.6 volts leads me to suspect you either have a poor contact on pin 1 of the 4 pin wiper connector, OR that you have a buildup of dirt between pin 1 and ground (pin 4). The latter HAS been seen before, by me and others, many times.

The consequence of the dirt, is that damp causes the BCU to keep on waking up, thinking that the wipers have not parked, applies power to the wipers, stops the BCU from sleeping, (maybe) activating the alarm, and, most importantly, RUNS the battery down.

And eventually, the battery starts to fail.

You need to CLEAN all dirt and debris from pin 1 of the 4 pin wiper connector.

Search this site for wiper issues. It keeps on occurring.

And replace the battery, which needs replacing.

Then repeat the tests.


By the way the maximum sleeping current of a R75 is quoted in post #16 as 0.045 amps, for a STOCK car. I believe that a Navall unit is a change, that MAY increase your sleeping current of your car up to 0.07A.

In post 41, SD1too talks about a current of 0.7A standby.

If this were 0.07A (because of the meter putting the decimal point in the wrong place), suddenly a standby current of 0.07A starts looking to be reasonable.

Or I might be talking myself up a blind alley.

And PLEASE PLEASE PLEASE, STOP switching the meter range to 200mA, you are potentially introducing errors, and blind alleys.

[sewerman]

Ok stupid question have you the old BCU to try reinstalling and see what happens.

2nd stupid question and I apologise if the answers in the thread but when testing the wires to the wiper di you leave it plugged in and use 2 needles to pierce the wires? I'm wondering if there's a pcb in the wiper that controls speed that may be failing and arcing ??

Sent from my SM-G977B using Tapatalk

[MarkS]

Questions are rarely stupid.

But answer can easily be stupid !

So, please don't apologize for asking questions that might appear to be stupid.

[Supervinnie40]

Originally Posted by MarkS

It is not unexpected.

The R75, like most modern cars, has self parking wipers. If the ignition switch is switched off, before the wipers have parked, the power is kept on to the wipers, until the wipers are parked.
This is achieved by having a contact in the wiper motor gearbox, that closes when the wipers are not FULLY parked. This is pin 1, the thin brown wire. This signal is fed INTO the BCU, which then commands the wiper relays on.

The fact that pin 1 was giving an unsteady voltage of 0.4-0.6 volts leads me to suspect you either have a poor contact on pin 1 of the 4 pin wiper connector, OR that you have a buildup of dirt between pin 1 and ground (pin 4). The latter HAS been seen before, by me and others, many times.

The consequence of the dirt, is that damp causes the BCU to keep on waking up, thinking that the wipers have not parked, applies power to the wipers, stops the BCU from sleeping, (maybe) activating the alarm, and, most importantly, RUNS the battery down.

And eventually, the battery starts to fail.

You need to CLEAN all dirt and debris from pin 1 of the 4 pin wiper connector.

Search this site for wiper issues. It keeps on occurring.

And replace the battery, which needs replacing.

Then repeat the tests.


By the way the maximum sleeping current of a R75 is quoted in post #16 as 0.045 amps, for a STOCK car. I believe that a Navall unit is a change, that MAY increase your sleeping current of your car up to 0.07A.

In post 41, SD1too talks about a current of 0.7A standby.

If this were 0.07A (because of the meter putting the decimal point in the wrong place), suddenly a standby current of 0.07A starts looking to be reasonable.

Or I might be talking myself up a blind alley.

The thing I found weird about the wipers, is that they never did this, and they where in the "park" position. I did some test yesterday, among a few where I tested if they worked properly. If they where in the correct position, they shouldn't have moved.
But looking at your other paragraph, regarding the BCU not fully understanding whether they are in the right position or not (dirty contacts and such), it does sound plausible that the system didn't know what was going on, and the BCU woke up on this and it all drained the battery.
I just never, ever had the wipers move without me using the switch. And my car is parked right in front of my living room (I like to look at it :P ).

Cleaning the contacts is good idea. As you can see on the photo, those are a tad bit dirty. Cleaning never hurts.

I did think of the Navall unit. In fact, I also considered the MG7 ATC console. But pulling those fuses, or just pulling the connector at the back of those units made no difference. From as far as my tests have shown, they have no effect on the current drain.

The battery does need replacing. I've been putting it off till I get the 0.07 back down to 0.03. It happened 2 times now that the drain killed the battery. I rather wear this broken one down while fixing the problem, instead of "damaging" the new one while trying to fix this.

Sorry, I don't know what the last sentence means? Not sure how to reply to that?

Originally Posted by sewerman

Ok stupid question have you the old BCU to try reinstalling and see what happens.

2nd stupid question and I apologise if the answers in the thread but when testing the wires to the wiper di you leave it plugged in and use 2 needles to pierce the wires? I'm wondering if there's a pcb in the wiper that controls speed that may be failing and arcing ??

Sent from my SM-G977B using Tapatalk

First question: no, I'm afraid I don't have the old BCU anymore. It has been 5 years and I don't remember where I left it. I do know I usually save all of this stuff in 1 place. But it's not there. I'm fairly organized and there is only 1 big box in the house where my carparts are stored.

Second question: I didn't pierce any wires. The connector for the wiper motor has a few spots where the metal is exposed. So its fairly easy to put the probes from the multi meter on those 4 pieces of metal. I did leave it plugged in. Otherwise the metal pieces I'm talking about won't be connected to the lead coming from the BCU. I have no clue regarding the PCB however. I've never taken the wiper motor apart.

Something that might be slightly interesting to know.
I just locked the car without the wiper motor connected. I then waited a bit more then an hour to check the drain. The previous time I did this (with the wiper motor connected) it would flucuate between 0.08 and 0.01. This time, without the wiper motor, it fluctuated between 0.04 and 0.01. While watching the meter go up and down for at least 5 minutes, it never got higher then 0.04.

[Supervinnie40]

I just cleaned the contacts with a bit of contact cleaner, a piece of wire brush I cut to fit and some contact spray. Unfortunately, this didn't help. Still at 0.07 amps when the wiper unit is connected. Pulling the big black plug still makes it drop to 0.03 amps. Putting the plug back in while the multi meter is still connected, makes the system wake up and go to 0.38 and eventually (after a few minutes) drop to 0.07 again.