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Chalkie

BM54 radio flattens battery in E38.

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Now this is odd. I bought a BM54 from eBay. Works 100% OK, except it flattens my battery overnight, so lets say 10 hours. I think I've checked common issues etc, but am somewhat bamboozled. Here's what I know/have checked:

  • Current through fuse F69 is zero, 15 seconds after key off. I haven't monitored it beyond that.
  • Car does appear to be going into sleep mode, 16 minutes after locking car, as I can see gear selector light go off.
  • Only my BM54 does this. I have 4 other radios, none have this issue, even after a week.
  • Disconnecting the BM54 connector prevents this issue.
  • Alternator works great, voltage at battery when running is approx 14.2V, battery charges up again no problems.
  • Nothing else to suggest any electrical problems with car.
  • I see repairers offering BM54 repair service that include for flattening battery issue - don't have any further details.

Anyone got any ideas?

Must be a good handful of amps to flatten battery overnight, so all I can think of is something 'waking up' periodically, but only when that radio is connected.

Considering using the switched 12V to supply the radio too, to see if that makes any difference.

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The eject box or ulf will keep the bm5x tuners powered up if it thinks a call is up. An aftermarket Bluetooth system can also do the same thing. Worth having a think about in your system.

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Thanks Neal, you mean via the TEL ON signal? I'm assuming that should be a non-issue once power is off, but it's gotta be something, will check behaviour of that line. Given there's 0 amps through F69 I do think it's something else being kept awake or woken up, but will check everything.

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Yes, Tel on, the bit2 / jbit / ulf will keep the signal high for as long as a call is in progress regardless of ignition state.

Aftermarket Bluetooth / iPhone devices use the same method .

This in turn leaves the bm54 on which in turn leaves the factory amp and aerial amp on.

I'd eliminate this as a source of your issue by measuring the voltage on pin 11 on the bm square connector. If this drops after ignition off the it's not your issue.

Also check pin 16 (ACC) to insure that the voltage drops after ignition off.

Either of this two pins will leave the system on if voltage is present.

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TEL ON (pin 11) is always on, bit less than 11V though. Is that actually normal in an E38/E39 with board monitor?

It remains on even if I disconnect the ULF, the BM54, and the amp (factory, & not DSP). Make me wonder what is asserting that line high.

Edit: obviously I'm testing that line at the loom connector. Hmmm, I do wonder about the behaviour of that line, is it just the TAA speedo signal?

Edited by Chalkie

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Assuming your car is the 97 740 in your profile...

Id be double checking the adaptor harness, I've seen cheap ones wired incorrectly...

TAA and TEL ON are not the same..??

if you are getting any V+ on TEL ON - find the source... cause it shouldn't... (without then phone being used of course)

if you do have a ULF fitted check the wiring on that adaptor also...

check that TEL ON and TEL Mute haven't been mixed up too

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Hi thanks for reply, yes is the 740 from profile - ex Japan, VIN 7-digit serial DK82078. Replaced 4:3 and Japanese radio, nav with 16:9 and BM54, Mk 4 nav, and added Gen 6 ULF. Wasn't pre-wired for phone, got ULF loom from BImmerNav and wired the round-pins to flat-pins radio adapter myself.

Odd thing is my calls via bluetooth work perfectly - can initiate or receive them, can terminate them, audio works correctly, radio mutes OK so the other line TEL MUTE seems to be acting correctly, and green phone call indicator on the 16:9 lights up when on a call. How does it know? I bus messages I reckon, will check.

PIN 11 on flat pins is same as PIN 10 on round pins right? I've seen more than one diagram refer to that as GAL (speed signal). I will put a scope on it and check.

And to confirm: disconnecting 12V direct from battery to BM54 does prevent the battery from going flat, and my last test did show current through F69. (Fed accessory 12V into both pins 15 & 16 of BM54).

Cheers, the adventure continues!

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Hi thanks for reply, yes is the 740 from profile - ex Japan, VIN 7-digit serial DK82078. Replaced 4:3 and Japanese radio, nav with 16:9 and BM54, Mk 4 nav, and added Gen 6 ULF. Wasn't pre-wired for phone, got ULF loom from BImmerNav and wired the round-pins to flat-pins radio adapter myself.

Odd thing is my calls via bluetooth work perfectly - can initiate or receive them, can terminate them, audio works correctly, radio mutes OK so the other line TEL MUTE seems to be acting correctly, and green phone call indicator on the 16:9 lights up when on a call. How does it know? I bus messages I reckon, will check. - Yes IBus

PIN 11 on flat pins is same as PIN 10 on round pins right? Yes I've seen more than one diagram refer to that as GAL (speed signal). I will put a scope on it and check. ​do not connect to the TAA line. this is to turn the amp on for a phone call if the radio is "off" - i.e. you can have the radio off but still have the monitor/nav etc on. this must be connected to the ULF only.

And to confirm: disconnecting 12V direct from battery to BM54 does prevent the battery from going flat, and my last test did show current through F69. (Fed accessory 12V into both pins 15 & 16 of BM54).- just confirm that.. 15 should have 12v all the time & 16 should have 12v with acc.

Cheers, the adventure continues!

Edited by Dogballs

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Once you've confirmed dogs balls suggestions Id be incline to run a direct line from the Ulf pin 33 to tel on pin 11 on bm54. I wouldn't expect to see this signal high with ignition off and no call up.

Suspect the operation is different on your old tuner module.

The only item in your current setup that would make use of the speed signal (assuming wheel pulse or speed averaged signal) is the MK4 navy unit. Even then its optional as the nav computer calculates average speed based on differential of GPS readings.

The old eject box can also be a source for tel on signal. Do you still have the old handset connected

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No handset, car has never had an eject box.

I'm not considering connecting TAA to pin 11 of the loom's radio connector, I am wondering if that's what the signal present on the loom already is. It remains high even after I disconnect the BM54 and disconnect the ULF. Weird huh?

Edit: @Neal, yeah I will direct from ULF to BM54 and see what that line does.

Edit: Right, I think I get it. PIN 11 on New Gen flat pins is not the same as PIN 10 on Old Gen round pins, for E38/E39 with LCD. On old gen, that was GAL (speed). BMW's documents for New Gen state that GAL is now via I Bus.

In summary:

  • Pin 10 on old gen is explicitly listed as GAL/Speed Signal in BMW official docs.
  • Pin 11 on new gen is explicitly listed as Tel On in BMW official docs.
  • I must disconnect Speed Signal from my radio, and ensure Tel On from ULF connects to radio pin 11.

Thanks guys, much appreciated, I will make the change tomorrow-isn and report findings.

Edited by Chalkie

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So what I don't get is this: if old gen pin 10 is GAL, and new gen pin 11 is Tel On, then I would expect to see some of the BMW retro-fit docs for new gen radios mention this, and where on earth would an old-new radio adapter cable get Tel On from? Very interesting stuff, really appreciate all the help on this forum, and can't wait to completely get to the bottom of this. Cheers!

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The difference is:

where you see in pin outs for Radios, it covers both headunits and radio modules...std radio will use 10 for GAL, but a nav radio module it will use 10 as TEL ON..

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Hmmm, all the WDS diagrams for 1st generation E38 show speedo signal on the old round pins pin #10.

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Sussed!

The difference is:
where you see in pin outs for Radios, it covers both headunits and radio modules...std radio will use 10 for GAL, but a nav radio module it will use 10 as TEL ON..

Nope, and that's the issue. Nav radio module old gen does not have TEL ON on pin 10. It has GAL on pin 10. GAL is active low, so by default is pulled high to 12V (even with key off). Hence my battery flat issue, since I'd connected old gen pin 10 to new gen pin 11.

Also, TEL ON does not go up/down with a call (unlike Tel Mute). As others have described, it's 12V if one or both of the following are true: R terminal is on, or call in progress. Only goes off when no call in progress and key off.

Works like a charm. Leaves one unanswered question - how come none of the BMW new gen radio retrofit docs mention this? You can't get TEL ON from an old gen nav radio module connector, so you need to run a wire to elsewhere.

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Had similar challenges when I tidied up the pervious owner of my cars nav Mk 4 retrofit. Brought the factory loom and the audio for the factory TV tuner audio stopped working. Both the retrofit guide and WDS weren't clear on which pins the nav audio and TV audio connect to if you have both. Worked it out in the end after I bounced it here for help.

The Ulf / Jbit2 replacement guide that hybrid ? did on here was great as well. Used it for the basis of my e46 install which has different colours in parts of the loom.

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