No Junk in My Trunk : help with sound system, pls

[js22]

I'm trying to get some sound working in my 1994 540i. It has a stock head unit and speakers.

Currently I get AM and Weather Band. No FM reception at all, and head unit displays "Disc Error". Sound is coming from the 2 speakers in the dash top only; using "fader" control, I can shift sound from left to right, although the movement is backwards : fade left makes right speaker loud, and v.v.

I understand that the rear window heater and the antenna share the same wires printed on the rear window. I presume this means the FM antenna, right ? Anyway, I did have occasion to use the rear window heater : it works just fine.


I crawl into the trunk, remove the CD changer, and check it's power : good 12 V. Besides, I can hear its guts working when I load the CD carrier.

The CD changer is a Pioneer : I'm pretty sure its not stock. Besides a 2-wire power connector that was spliced into the wiring harness, there is a rectangular multi-pin connector with 10-ish feet of cable that adapts to the BMW circular DIN connector with 5 + 9 pins.


Next, I completely remove the rigid carpet-like stuff from the drivers( left) side of the trunk. No amp there.

Not only is the amp not there, but it's not clear to me how an amp would be connected. There are the two cables for the CD changer, one bundle that snakes to the trunk lid, and some really fat (1" dia) bundles routed along the floor of the trunk, but with no connectors or cut wires in sight. No signs of PO butchery.

I go back to the head unit and pull it out. It looks like all of the OEM connectors are there. On the big rectangular pin-housing connector, each wire has been cut, but cleanly re-connected with crimp connectors. I didn't check super carefully (it was dark...) but all the colors seem to match up. Couldn't find anything loose, missing, or screwy looking.

So the questions :

1) On a 1994 540i, is the stock amp really, really, always, and only located in the trunk, on the left hand (US driver's) side, behind the rigid carpet stuff ?

2) If so, can somebody point me to a photo or drawing or description of exactly where the input/output cables and connections to the stock amp can be found ? Shouldn't they come out from the same bundle with the CD changer cable ? Without locating that I'm SOL.

3) Is it possible for the stock head unit to drive one pair of speakers directly, without an amp at all ?

4) About the FM reception : Is it possible for the rear window heater to work just fine but the FM antenna be completely non-functional ?

BTW: On my last car, after the second antenna broke off, I left it completely disconnected, and just with the coax cable end lying in the trunk I was able to pick up all but the weakest of local stations !

Anyway, as always, help very much appreciated.



The saddest part of this is that I've got really, really low expectations regarding sound : I'm sure the stock amp, speakers, and amp would be more than good enough for me.

[David325e]

If you can look into the trunk see on the left side and see some interior sheet metal and then the outer sheet metal then the amp is gone. Its in there in the middle. And that connection doesn't sound stock to the 540, maybe from an E39? Post a pic of it.

As for the rear lines, the lines are not shared. I.E. theres 8 for each function so it'd be possible to have one not working, but not likely. These systems are always abused so sounds like someone got ripped off on an ebay sale of the cd changer and hacked it in. Or had a nice system in place and put the stock back in poorly. Happend on a few previous bimmers of mine.

[js22]

Okay, so I guess I'm an idiot. But an idiot with questions !

I went back out to the trunk and on the *third* try I found the amplifier. Maybe I was expecting it to look more amplifier-ey ???

So strike questions 1-3. (sorry).

Still wondering :

4) (from above) Can the rear window heat function if the antenna module does not ?

5) Where is the fuse for the FM antenna antenna booster thing ? I looked in the fuse box under the hood in front of the driver and didn't see anything that looked related.

6) Does all power to the amp come from the radio ? My radio is certainly getting power. Is there a fuse between the head unit and the amp ?


For my next free daylight hours (whenever that might be) I plan to crawl around with a voltmeter and see if I'm getting power to the amp, check continuity, etc.

In the meantime, I've got enough frustration built up, I think I'm gonna go for a drive, then have an attitude adjustment.

[David325e]

Hm, not sure on that. Luckily I've never had many electrical gremlins with the E34s. But, I am having a problem right now where my rear defroster doesn't work but my radio antennas do haha!

Theres no module for the defroster, but the fuse and relay are located under the rear seat. Lift up the rear seat bottom (pull like heiL) and on the driver's side theres another power distribution block. It should be labeled and the antenna or amp fuses could be there.

The antenna modules themselves are located behind the c pillar covers. Pull at the top of it and then just pull them off is really the whole process. There you'll see them and can check for power there I guess. BTW there may well be an unused ground back there because of the lights, but as long as all the plugs on the antennas are used you should be fine.

Check your voltage at battery terminals and see what you're getting and I'll go check the Bentley and let you know what I see.

Things involved are:
1 relay in front fuse box
fuse 36 (30A) in rear box
Fuse 18 (15a) front box

Fuse 35 (30A) rear box
Rear relay for defogger

Think the last two are out because your defogger works.
CD changer is grounded to head unit
Check the ground from the amp, they share a common ground
Fuse 36 is constant, fuse 18 is acc

Maybe someone knows if a bad amp will also cause bad reception.

[quick93]

I've got a good working amp out of my 94 for sale, just upgraded the entire system in my car.

[js22]

Okay, so I've learned a little bit.

CD CHANGER
----------------

The CD changer is a Pioneer CDX-M30. Using a DMM I checked all the connections described on this page :

http://www.bavtech.com/e34-guides/19...o-adapters.php

And everything tests out correctly (i.e., same pin connections as BMWPIO/M).

By pressing "prog" and "-" simultaneously on the head unit, I learned that it is an ALPINE3. This head unit is reported to work with the CDX-M30.

I also realized that the link to the CD changer is basically working. It detects the presence of discs (and lights up the buttons 1-6) and I can hear it changing discs when I press the buttons. Each time, there is a long (10 seconds ?) pause before it reports DISC ERROR.

So I'm thinking everything is okay with the wiring, etc., and that the changer is bad (or dirty).


AMP
-----

I messed around with the amp (tried to disconnect it, but connectors are stuck). That, plus messing around with the head unit must have jogged something, b/c now all speakers are working.

I can hear AM radio just fine

FM Antenna
--------------

I pulled off the C-pillar covering on the drivers side and found the antenna/rear defroster unit. With the radio on, I checked voltage on the brown connector and got 10.8 V.

I removed each of the coax wires one at a time and re-connected them. I verified that one killed AM reception and one killed WB reception. Still no FM reception.


So I guess I'm down to one question : Why no FM ?

Anybody ?

[attack eagle]

head unit problem most likely.
Did you verify it is actually plugged in at the radio? any chance of trying a different head unit?


Congrats on your persistence and willingness to learn and get your hands dirty.
I see a fat wallet in your future.

I cna almost guarantee that the laser lens is contaminated and unfortunately possibly out of alignment. You can clean it with water and alcohol (rubbing alcohol leaves residue also so alternate one with the other until clean).

It is no good with a newer unit, like a CD43 or c43, so if the head is bad, it is time to ditch the changer and go Ipod control or aux in.

[js22]

At this point I've pretty much decided to get a new (non-BMW) head unit.

I did, however, find one thing kind of screwy.

I pulled off the passenger side C-pillar cover and found the second antenna/heater module. What is strange is that there is a place for a plug, with nothing connected. It is a round, snap-in connector, which on the drivers side looked like it delivers power.

I looked all over, and couldn't find a loose wire anywhere; maybe it got pulled down behind the rear seat ?

I think for now I'll wit for finances to recover a bit, buy a head unit (CDs, USB stick.) and hope for the best with FM; if not, I'll have some more digging to do.

[js22]

[head unit arrives]

So I got my new head unit and wiring adapter from Crutchfield.

Soldered and heat-shrunk the wires by color, plus "P. Cont." to "antenna power".

Everything works fine, including FM.

Conclusion : FM tuner in old HU broken, CD changer broken, Antenna was working all along.


NOTEs on antenna(s) :
-------------------------
The car has two FM antennas (wires on rear window), and two antenna amplifiers : one on each C pillar. The stock system combines the two signals (electronically) with an adjustable phase to overcome multi-path interference effects. Aftermarket head units (all that I've seen) do not make use of the second antenna.

In the dash, there is a "normal" sized co-ax and a smaller coax for the two antenna signals. Only the normal sized one is used for aftermarket HU's. Also, it happened that the passenger side C-pillar antenna amp in my car did not have any power connected - I couldn't even find the wire. And my FM reception is pretty decent (much better than stock, which was broken...)

The only warning I would give about disconnecting the passenger side antenna amp is that I have no idea how the RF-based keyless remote/alarm gets its signal. I think I saw a post saying it also came from the rear window wires. I don't have a keyless entry fob, so I have no way of testing it at present.


BTW, The head unit I got is a Kenwood KDC-MP342U. It had all the features I wanted : cheap, has a volume knob and station preset buttons, plus USB input. The sound is plenty good enough for me.

The one drawback is it's ugly as butt; and no, not a nice butt. After dark, it looks like a drag queen after a glitter party. And although you can dim some of the display (manually), the worst offender is the screaming blue LEDs that can't be dimmed.