Parasitic Drain & Relay/Door moudules

[Money Pit]

Hi All,

Firstly, I normally use my '95 840 as my daily driver, 5 days a week, clocking up 96 kms per day - 1/3 highway @ 100 kph, 1/3 main road 60-80 kph & 1/3 in traffic 40-60 kph. About an hour each way.

GM caps replaced December last year (self). Bosch factory rebuilt alternator (FCP) fitted July 17.

Due to heavy rain I used the other car for 4 days so the 840 sat in the driveway. On the seventh day I went to use the 840 again and found flat batteries. I charged the batteries over a couple of days to around 12.8 v.

The following week end, I researched the forum's and did some testing. Timms and may others tips and instructions shave been a great help so far.

Here is where I am at:

Current draw after more than 16 mins is still around 460 milliamps
Consumer cut out relays K72 & K73 are hot (but not clicking)
Removal of Consumer cut out relays K72 & K73 drops current draw to 220 mA
Removal of AC Blower relay K4 makes no difference
Removal of wiper relays makes no difference and wipers work in all modes.
Removal of Relay Module increases current draw (?) (no signs of water ingress or visible damage)
Current measured across fuses F33 (2.3 mA), F42 (0.9 mA) & F43 (0.5 mA)
Removal of fuses F33, F42 & F43 results in current draw dropping to 60 mA (Shangri La reached )

So where to next?

Is there a common problem or fix for the relay module?
Should I be looking at the door modules as the source of the problem?
How can I test or rule out the GM as the source?

I should point out that most electrics work as they should - windows, lights etc. I do have intermittent alarm triggering but suspect that may be due to 34 deg C most days this summer, and I still haven't fixed the air-con.

Unfortunately, BMW only sold about 370 E31's in Australia so finding one to swap modules with is not readily accessible. I have only seen 2 others on the road in the last 4 years - both when I was driving a different car

[Timm]

As K72 and K73 are hot - then the relay module is holding them on - and the relay module is controlled by the General Module. But, what confuses me is that the current doesn't drop when the relay module is removed, and that should have switched off the consumer relays - and dropped the current.

But, saying all that - it does sound like a GM problem - it certainly has all the hall-marks of its behaviour!

[EEDegreeToDrive]

Hi All,

Firstly, I normally use my '95 840 as my daily driver, 5 days a week, clocking up 96 kms per day - 1/3 highway @ 100 kph, 1/3 main road 60-80 kph & 1/3 in traffic 40-60 kph. About an hour each way.

GM caps replaced December last year (self). Bosch factory rebuilt alternator (FCP) fitted July 17.

Due to heavy rain I used the other car for 4 days so the 840 sat in the driveway. On the seventh day I went to use the 840 again and found flat batteries. I charged the batteries over a couple of days to around 12.8 v.

The following week end, I researched the forum's and did some testing. Timms and may others tips and instructions shave been a great help so far.

Here is where I am at:

Current draw after more than 16 mins is still around 460 milliamps
Consumer cut out relays K72 & K73 are hot (but not clicking)
Removal of Consumer cut out relays K72 & K73 drops current draw to 220 mA
Removal of AC Blower relay K4 makes no difference
Removal of wiper relays makes no difference and wipers work in all modes.
Removal of Relay Module increases current draw (?) (no signs of water ingress or visible damage)
Current measured across fuses F33 (2.3 mA), F42 (0.9 mA) & F43 (0.5 mA)
Removal of fuses F33, F42 & F43 results in current draw dropping to 60 mA (Shangri La reached )

So where to next?

Is there a common problem or fix for the relay module?
Should I be looking at the door modules as the source of the problem?
How can I test or rule out the GM as the source?

I should point out that most electrics work as they should - windows, lights etc. I do have intermittent alarm triggering but suspect that may be due to 34 deg C most days this summer, and I still haven't fixed the air-con.

Unfortunately, BMW only sold about 370 E31's in Australia so finding one to swap modules with is not readily accessible. I have only seen 2 others on the road in the last 4 years - both when I was driving a different car

Bench testing reveals that without the relay module, the general module is certainly not happy--

All signs point to your General module capacitors..
Removing your wiper relays will also prevent the car from sleeping (as there is no wiper park confirmation)!
(So will removing the Wiper Pressure control relay, if your car has that option, or is coded for it incorrectly)

See here:
https://www.bimmerforums.com/forum/s...-Bench-Testing

Final current should be less than 50mA, typically ~42mA.

[Money Pit]

Hi All,

Thanks. It looks like I will need to go over the GM again. I'm not a tech but I did go over my capacitor replacement work with a magnifier and thought I had "nailed it". (I was pretty pleased with myself at the time that it seemed to go without the usual incident requiring additional parts or duct tape).

Could the caps in the Relay Module be bad as well?

[EEDegreeToDrive]

Hi All,

Thanks. It looks like I will need to go over the GM again. I'm not a tech but I did go over my capacitor replacement work with a magnifier and thought I had "nailed it". (I was pretty pleased with myself at the time that it seemed to go without the usual incident requiring additional parts or duct tape).

Could the caps in the Relay Module be bad as well?

Hmmm... I missed the part where you replaced your capacitors last year. In the ~75 that I've repaired, I've seen a lot of botched jobs, but I'll give you the benefit of doubt for the moment. I assume you didn't do the sleep current test right after repairing your GM like a good DIY technician? :-)

Check out my thread on General Module sleep explanation.. I don't think your relay module capacitors would help you out.. The caps in the GM are the ones that buffer it from voltage swings that cause the GM program to restart, RM caps don't affect anything significant. It's possible that a relay is sticking on, but very unlikely.

A few things:
1) Your GM may be corrupted or defaulted to european coding (with options you don't have) (see my post) - You'll want to connect up INPA and read the GM codes and coding, post screenshot. If you see an option your car doesn't have, you'll need to use NCS or something to recode it to the sticker in your fuse box.
2) You may have a problem with your door modules if the car is sleeping then waking (set up your current test, close the door, and watch it as it approaches 16 minutes and see if anything changes (a few cilcks at the 16 minute mark, then waking back up, etc)
3) You may have an issue with a missing/bad wiper relay, or APV if you car has that
4) You botched the GM job with a solder blob, cut trace, cold solder joint, tacked a part onto a lead that subsequently broke first bump you went over, etc (see, I gave you the benefit of doubt for the first 3 :-) ) If you do get the GM out, send me a photo of both sides and I'll check across the big pond...

[Money Pit]

Hi All,

I have performed some more tests today:

1. Current draw after 16 mins is still 460 mA
2. Current draw after 16 mins with only left hand (passenger) side door module unplugged 430 mA
3. Current draw after 16 mins with both door modules unplugged 430 mA
4. Current draw after 16 mins with only right hand (driver) side door module unplugged 430 mA
5. Current draw after 16 mins with all door modules reconnected 460 mA
6. Current draw after 16 mins with General Module removed 37 mA

I guess it all points to the GM. So I suspect either my cap replacement is suspect or the GM defaulted to a different coding. Time to pull the GM apart again.

[EEDegreeToDrive]

Hi All,

I have performed some more tests today:

1. Current draw after 16 mins is still 460 mA
2. Current draw after 16 mins with only left hand (passenger) side door module unplugged 430 mA
3. Current draw after 16 mins with both door modules unplugged 430 mA
4. Current draw after 16 mins with only right hand (driver) side door module unplugged 430 mA
5. Current draw after 16 mins with all door modules reconnected 460 mA
6. Current draw after 16 mins with General Module removed 37 mA

I guess it all points to the GM. So I suspect either my cap replacement is suspect or the GM defaulted to a different coding. Time to pull the GM apart again.

Yeah-- 460mA is basically "not asleep". To keep your car drivable, you could pull the consumer cut out relay (one CCR powers the other, so you just have to pull the correct one)
Double check your wiper relays and APV relay if you have that option.

(Note: It might be faster to check your coding by getting some BMW diagnostic software up and running and checking out the GM for faults.. The coding display in INPA will quickly reveal that things are corrupted if you see headlight washers/wiper pressure control 'checked' if you don't have those options.

Send me photo of the top and bottom side of your board and I'll take a look at your job. use macro on a digital camera, or on your phone..

And if I could ask a favor.. After you get it solved (car sleeping like a baby after 16 minutes), while you still have your doors apart, could you repeat your test with the door modules disconnected? I'm curious if the car will sleep properly with one or more of the door modules missing. (Future note: the fastest way to see if the car sleeps is if it turns a manual dome light and/or trunk light off after 16 minutes)

Also be aware, the battery needs to be disconnected before the GM is reconnected (and possibly before it is disconnected) because it does poll some of the modules for features/presence I believe
Good luck!

[Money Pit]

<sub>Hi,

Thanks for the info. Its been a busy week at work but I have finally gone a little further with this. I pulled the GM and went over it with a microscope at work. I wasn't happy with the job I had done last year so I decided to redo the cap replacement and clean up my work. These photos are the original repair:</sub>

1st repair 1.jpg1st repair 2.jpg1st repair 3.jpg1st repair 4.jpg1st repair 7.jpg

[Money Pit]

Hi All,

Photos of the GM after the second repair. I purchased a proper desk illuminated desk maggy (magnifying) lamp for about AU$65 to assist. Note to self if you smell burning plastic, there is probably burning plastic (the soldering iron went a little too close to the cover panel):

2nd repair 1.jpg2nd repair 4.jpg2nd repair 5.jpg2nd repair 7.jpg

So I reinstalled the GM and ran the current test again. Still 460 mA current draw after more than 16 minutes. I pulled both Consumer Cut Out Relays and the current draw dropped to 220 mA.

So I guess the next step is to find someone in Brisbane with INPA to read/recode the GM.

[EEDegreeToDrive]

Hi All,

Photos of the GM after the second repair. I purchased a proper desk illuminated desk maggy (magnifying) lamp for about AU$65 to assist. Note to self if you smell burning plastic, there is probably burning plastic (the soldering iron went a little too close to the cover panel):

2nd repair 1.jpg2nd repair 4.jpg2nd repair 5.jpg2nd repair 7.jpg

So I reinstalled the GM and ran the current test again. Still 460 mA current draw after more than 16 minutes. I pulled both Consumer Cut Out Relays and the current draw dropped to 220 mA.

So I guess the next step is to find someone in Brisbane with INPA to read/recode the GM.

1st repair didn't look terrible, maybe some less-than-ideal flowed traces, but nothing that jumped out as a red flag. The 2nd repair photos look great.

Note: Per my thread on the E31 sleep current analyis, If your wiper pressure relay (aka APV) or wiper relays are missing or bad, that'll keep the car from sleeping.

Reading the coding and errors logged is probably the best approach. The TinyADS interface (http://openlabs.co/projects/Tiny-ADS-Interface) on ebay is pretty decent. You'll have to jump through some hoops to find the BMW diagnostic software and get it installed since it's all stolen. My gut feeling is that the programming get corrupted, or simply reverts to European defaults under certain circumstances. At least if your module is coded correctly, you'll be able to see and clear any kind of screwy general module errors logged.

Good luck.. In the mean time, for extended durations parked(>a few days), you can pull the consumer cut out relays, though 220 still seems high with the relays out. (technically, pulling one disables the other, but I don't know if it's the top that disables the bottom or the opposite)