charge trek VIII -"Scottie, break out the ETM!"

[tim eh?]

Alrighht .... were you all hoping this would go away by itself? me too.


For those of you who didn't make it through the first seven (!) episodes...
...the story so far...


Basically, an inexplicably bad charging system on my '89 525i has led me to investigate the circuit that connects to the D+ terminal at the alternator, which reads 1.5V (should read +/- 12.5V) with the engine running. The meter shows that there are 48.4 ohms of unwanted resistance somewhere on this circuit that I have to find, preferably before my workspace turns into planet Hoth. (http://www.bimmernut.com/forum/picture.php?albumid=7&pictureid=73)

Let's have a look at that circuit in the trusted Bentley that we all have a copy of, shall we?

http://www.bimmernut.com/forum/attachment.php?attachmentid=6291&stc=1&d=1226809251http://www.bimmernut.com/forum/attachment.php?attachmentid=6292&stc=1&d=1226809251

The link to the instrument cluster is for the charge light, which works as it should. Hmmmm... better have a look at that 'uncoupling diode' and the 'unloader relay'. As it turns out i have a couple - both of which seem to work, each with it's own clue.

http://www.bimmernut.com/forum/attachment.php?attachmentid=6283&stc=1&d=1226784448http://www.bimmernut.com/forum/attachment.php?attachmentid=6270&stc=1&d=1226690723
http://www.bimmernut.com/forum/attachment.php?attachmentid=6280&stc=1&d=1226784479http://www.bimmernut.com/forum/attachment.php?attachmentid=6282&stc=1&d=1226784448

An unloader relay is designed to reduce draw on the battery from vehicle electrical components during vehicle starting so as not to overtax the battery, from what I can gather. I think it activates the diode which regulates voltage to certain circuits. (?.....help?)

Time to break out the ETM...

[tim eh?]

so here is a more detailed chart. the arrows point to the burn marks i found.
http://www.bimmernut.com/forum/attachment.php?attachmentid=6295&stc=1&d=1226811165

here is the supply to power sources B, G, and H, all of which seem to operate through some kind of switch. Seems they are 'hot at all times'.
But what does 'partial' mean?
http://www.bimmernut.com/forum/attachment.php?attachmentid=6293&d=1226811139

H leads to the ignition switch. From this chart we can see C is active in pos3 (start) and pos2(run), while A is active in key positions 1,2, and 3.
http://www.bimmernut.com/forum/attachment.php?attachmentid=6296&stc=1&d=1226812129

and here is something related i think... the final stage blower control unit, which had a meltdown last spring (http://www.bimmernut.com/forum/showthread.php?t=38910) (shortly before the first alternator died).
http://www.bimmernut.com/forum/attachment.php?attachmentid=6294&stc=1&d=1226811206

So.... I think I'll sleep on it for a bit.... but there's something to this i think.

Or maybe there is something wrong at that link... which is supposed to be in the front power distribution box.... but I'm not sure where.
Underneath somewhere I'm guessing. :(

Well... that's where I'm at - ideas are most welcome. Those are the clues I'm looking at. Something up with that B power feed... guesses?

Any tests I should do.... something I can look for...

[tim eh?]

here's maybe something i can look for...
http://www.bimmernut.com/forum/attachment.php?attachmentid=6297&stc=1&d=1226818218
http://www.bimmernut.com/forum/attachment.php?attachmentid=6298&stc=1&d=1226818218

[attack eagle]

ok, the diode in the relay is 'flyback' protection. when you shut the power off to a relay the collapsing field sends a voltage spike back to the switch. the diode provides a path to ground for the induced spike, and helps reduce arcing (and carbon build up) at the switch itself.
it is NOT anything to be concerned with.

[tim eh?]

ok, the diode in the relay is 'flyback' protection. when you shut the power off to a relay the collapsing field sends a voltage spike back to the switch. the diode provides a path to ground for the induced spike, and helps reduce arcing (and carbon build up) at the switch itself.
it is NOT anything to be concerned with.

I understand most of that - I don't get "the diode in the relay" - what relay?

[Tiger]

Tim... STOP... you have to think of KISS... Keep It Simple Stupid!

First thing to do is the bulb... you said it work, but you never said if it is bright or dim... What would break first in the entire electrical system? Bulbs... so investigate the bulb... make sure you got 12V there.

My next suspect is if you don't get 12V at the cluster, then it has to be the ignition switch... that part is high wear item...

[tim eh?]

Tim... STOP... you have to think of KISS... Keep It Simple Stupid!

First thing to do is the bulb... you said it work, but you never said if it is bright or dim... What would break first in the entire electrical system? Bulbs... so investigate the bulb... make sure you got 12V there.



ok.... i stopped.... kind of...

...did you just call me stupid? :D

ok, so investigated the bulb. i can't figure out how i would measure voltage in the clusterboard with the ignition on, so i figured the easiest way would be to swap in the spare cluster i have, which i did.

in both clusters the bulb works as it is supposed to, and is bright, just as bright as all the others. it comes on before and during start then shuts off, also flashes (once) on shutdown.

i went for a testdrive with the spare cluster in and had the same poor charging results.

so can we rule out the cluster / bulb / resistorbehindthebulb ?



My next suspect is if you don't get 12V at the cluster, then it has to be the ignition switch... that part is high wear item...

hmmm.... remember this (http://www.bimmernut.com/forum/attachment.php?attachmentid=6273&stc=1&d=1226697972)?

here's a better photo

http://www.bimmernut.com/forum/attachment.php?attachmentid=6300&stc=1&d=1226853466

here's the etm again, with the PO's splices marked with caffeine-laden arrows.

http://www.bimmernut.com/forum/attachment.php?attachmentid=6301&stc=1&d=1226853996

what am i doing still in front of the computer?

[bad_manners_god]

Open up those ignition switch wires and re-solder them properly.

[tim eh?]

comments?

[bad_manners_god]

comments?

Defiently the problem, or at least part of it, replace the wires from the first splice to the last and solder the connections, no crimp connectors for this.

Same problem for a friend with a 2001 Elantra...Had an aftermarket alarm installed when he bought it and then after 4 months his starter would work whenever it felt like it, so I opened up the dash and took everything out, EVERYTHING, didn't leave a single wire, re-soldered the ignition wires and everything works again.

After you fix them, check D+ again

[BMWDriver]

It's worth rewiring those, I'm sure you'll take care of that, but being how recent your problem is, I have some doubt it's the source of the problem, unless something in there shifted.

At this rate, you'll know how to wire that car front to end blindfold ! ;)

[tim eh?]

It's worth rewiring those, I'm sure you'll take care of that, but being how recent your problem is, I have some doubt it's the source of the problem, unless something in there shifted.

At this rate, you'll know how to wire that car front to end blindfold ! ;)

i wish i didn't but i agree. i tried to find a bad spot in them but i couldn't - nice readings from the ignition switch to the other side of the frayed/spliced bits. i think maybe the little cut bits might have caused the short in the unloader relays, and maybe were the cause of the battery drain... i have to remember to check bat voltage tonight.

temporary fix - i did a better tape job and cut the bits off.... (had to run...) no change... those wires have at least 90% wire left and the original solder looks solid, but i'm on it.

but i should test the ignition switch too... bentley only has procedure for removal. i guess i check the ignition switch at the solder points with the key in appropriate positions. but i don't think i want to put any voltage through the car while i'm doing that.... what do i do?

also should test alternator but i am assuming it is good... the last one came with results from 6 tests.... man i feel so bad about taking all those alternators back. i already went in and talked to the guy and he doesn't seem too pissed. i will also test voltage at the end of the lead to the D+ and see what happens with load after a few minutes.

some of that wiring for the alarm was behind the stereo too... could check that out i guess.

i feel it's pretty safe to rule out the cluster. (...?)

i found that 'unused' blue wire i think (at plug X512), it's very easy to access - i tried to test for voltage but i didn't get any... should i?

i'm still extremely suspicious of those unloader relays. especially the one with two giant burn marks on the terminals. i hooked them both up to 12V and measured resistance for 10 minutes but both were < 0.5ohms and didn't suddenly jump up to 48 or anything like i was hoping they would. i have googled it a bit and it seems to be the recommended solution for a few problems like mine in other bmws, vws, porsches i have seen... so i'm tempted to grab it tomorrow and see if it helps... probably a waste of time and $30.... (...???)

i think i am discovering the car at a good rate now, but it's a bit stressful with winter coming. i bought it mostly for winter - heh silly me!

[BMWDriver]

There's an electrical/electronics shop I go to every once in a while for wires, switches and all : Addison. It's on 20th Ave, right off of Metropolitain, north of it. They may be able to help you with testing your relay, or at least help you figure it out.

http://www.addison-electronique.com/

Show us the spark burns again ? From the pics in this thread, it doesn't look like the relay's been burned (the orange one).

How's the relay box itself ? Can you unbolt it and look underneath ? Is it ageing ?

[tim eh?]

There's an electrical/electronics shop I go to every once in a while for wires, switches and all : Addison. It's on 20th Ave, right off of Metropolitain, north of it. They may be able to help you with testing your relay, or at least help you figure it out.

http://www.addison-electronique.com/

Show us the spark burns again ? From the pics in this thread, it doesn't look like the relay's been burned (the orange one).

How's the relay box itself ? Can you unbolt it and look underneath ? Is it ageing ?


Thanks - I have heard about that place but didn't know where it is. I'm really lucky - the TV repairman round the corner loves to chat and likes cars!

The orange relay looks good, it's the brown one that is very suspect.

They look the same but they are different i think. I think the orange one is #2 and the brown one is #3.
http://www.bimmernut.com/forum/attachment.php?attachmentid=6277&stc=1&d=1226708697

doesn't this look suspicious to you? especially seeing as it's directly in the bad circuit!
http://www.bimmernut.com/forum/attachment.php?attachmentid=6270&stc=1&d=1226690723
but it tests ok...


the relay box looks like this - i've eaten off dirtier tables...
http://www.bimmernut.com/forum/attachment.php?attachmentid=6279&stc=1&d=1226760250http://www.bimmernut.com/forum/attachment.php?attachmentid=6283&stc=1&d=1226784448

but i haven't looked underneath yet... there is this suspicious terminal at the plug for the orange relay, but it doesn't look burned...


yes - a look underneath would be in order i think....

[Ferret]

Something has just sprung to mind, can you do the following tests for me when you get a chance?

Measure the voltage at the D+ plug with the ignition on; while the plug is plugged in and while the plug is unplugged.

Take the battery out of the car, leave the ignition on and the D+ cable unplugged from the alternator:

Measure the resistance from the D+ terminal on the alternator to the case of the alternator
Measure the resistance from the D+ connector on the cable to the battery + lead

[BMWDriver]

Yup, now that I see it, it does look suspicious.

Addison has a lot of goodies : speakers and woofers of all kinds for your car or home, resistors, capacitors, computer goods (keyboard, mouse, box, power), cabling and connectors, tools, meters... I kind of get a kick out of every trip over there. Got my self-re-made hood's grounding cable parts from there.

[tim eh?]

Something has just sprung to mind, can you do the following tests for me when you get a chance?

Measure the voltage at the D+ plug with the ignition on; while the plug is plugged in and while the plug is unplugged.

Take the battery out of the car, leave the ignition on and the D+ cable unplugged from the alternator:

Measure the resistance from the D+ terminal on the alternator to the case of the alternator
Measure the resistance from the D+ connector on the cable to the battery + lead

not sure i follow, ferret...

remove battery from car but leave cables attached?

how far out of the car?

[Tiger]

What he wants you to do is measure the resistance... from D+ to battery positive cable... with ignition on and battery disconnected.