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E34 (1989 - 1995)

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  #1  
Old 04-03-2017, 07:11 AM
yatepa yatepa is offline
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Location: Loveland, Colorado
 
Join Date: Feb 2016
Posts: 10
Mein Auto: 1995 540i
Alarm, Horn and Hazard light GREMLINS

May of 1995
540i
Wired for cellular phone originally, probably bypassed with a jumper under the center console (unconfirmed).
No relay in the ebox tied to horn and phone, no socket.


So when I first purchased the car, the remote key worked.
It doesn't now, and hasn't for at least a year. The key itself has been tested functional.

The OBC by the radio worked, but it is out as well. I swapped for a known working unit, still no function.

The hazard lights have never really worked properly. Upon connecting the battery, sometimes they flash and sometimes they flash and the alarm claxon sounds, but only for 3 seconds. If you press the hazard switch once, they stop.
Under normal operating conditions, the hazards only stay on if you hold the switch down.

The push-button horn on the steering wheel did function before everything else went bad, but it is out with all the rest of it.



I have a factory alarm & separate obnoxious claxon horn, absolutely. It is unlike what is pictured on realoem for my month and year.
A friend at the local sports car shop told me that there were some 540i's that shipped in this configuration. This also may have been an aftermarket "solution" put in place by the PO, possibly, though I doubt it.

I have a computer with the "hidden" fuse under the rear seat. It has a 4 pin power plug-in as well as 2 connectors, one white, one black. 65758366229 U

There is another computer black box behind the center console, radio and OBC. It has the same style black and white connectors as the rear one, and is accessible from the right side by removing the carpet panel from the side of the center console. I have not yet removed it from its home, but it seems if I can get the wires disconnected, it should slide out.

I pulled apart that rear computer, and found 2 capacitors on its PCB that are toast. One is 39uf at 25V (rated 105F) and the other is 100uf at 63V (also 105).

I'm hoping that restoring those will restore my remote key, OBC, alarm, and service horn. Maybe even my hazards will function normally, but seeing as how that system's switch has always worked like a momentary, I wonder if the wires connected to it aren't hooked up backwards or something.

It seems sort of obvious now, but finding confirmation that the horn and flashers are tied into the alarm system took more research then it should have, and that is why I'm posting here without posing an actual question.

My diagnosis?
If the caps on the rear computer fail, it behaves just like pulling its fuze, a method some posters have posed as an alarm bypass.

I am sure not everybody is terribly interested, but hopefully voicing my woes here will be helpful for someone.

If I find success, I will post some pictures and part numbers to make this even clearer.
If I don't get joy, I will pull the 2nd computer behind the console and investigate its innards, and report back.

Any constructive input from other users with experience in this would be appreciated.

Last edited by yatepa; 04-09-2017 at 02:27 PM.
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  #2  
Old 04-09-2017, 01:41 PM
yatepa yatepa is offline
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Location: Loveland, Colorado
 
Join Date: Feb 2016
Posts: 10
Mein Auto: 1995 540i


So I extracted this tertiary computer from behind the dash after replacing the relay module behind the backseat.
65758366229 U

The stem switch actually got a reaction on the cluster from the OBC, even though the OBC still behaves like it is dead with my rear computer repaired and replaced.

Previously, the stem switch did nothing.

I think I am on the right track, and have faith that re-capping this third computer (which actually has three plugs, not two), will restore my remote key function, my hazard lights, my alarm, and most importantly, my horn.

Most of its caps look really blown. Judging by its placement and configuration, and lack of wiring to the right C pillar, I think it is safe to say that the receiver for the key is in my mirror.

I'm going to look at the E39 on realoem for insight. I have a hunch what I am working with is more like the newer, and most certainly is not wired like anything typically found in the E34 generation.

Again, any insight would be helpful.

Last edited by yatepa; 04-09-2017 at 02:29 PM.
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  #3  
Old 04-09-2017, 04:07 PM
south26 south26 is offline
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Location: Dayton, OH
 
Join Date: May 2009
Posts: 1,509
Mein Auto: 535i 1989
are you talking about the gm and the rm under the rear seat?


Andy
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  #4  
Old 04-09-2017, 04:26 PM
yatepa yatepa is offline
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Location: Loveland, Colorado
 
Join Date: Feb 2016
Posts: 10
Mein Auto: 1995 540i
The new picture is not the GM (under the hood in the ebox) nor the relay module in the back seat.

This computer was located near the firewall behind the radio and the OBC, at the back of the center console, accessible by removing the glovebox and a heat duct.
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  #5  
Old 04-09-2017, 05:42 PM
south26 south26 is offline
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Location: Dayton, OH
 
Join Date: May 2009
Posts: 1,509
Mein Auto: 535i 1989
Quote:
Originally Posted by yatepa View Post
The new picture is not the GM (under the hood in the ebox) nor the relay module in the back seat.

This computer was located near the firewall behind the radio and the OBC, at the back of the center console, accessible by removing the glovebox and a heat duct.
The Gm is under the rear seat not the hood. Not sure what you are talking about, I have parted a number of these cars and there is nothing behind the OBC that controls anything but the heat/ac and fan


Andy
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  #6  
Old 04-09-2017, 06:06 PM
yatepa yatepa is offline
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Location: Loveland, Colorado
 
Join Date: Feb 2016
Posts: 10
Mein Auto: 1995 540i
Ok, so I am barking up the wrong tree, after I searched the part number on the case, that component does appear to be the fan blower control.
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  #7  
Old 04-09-2017, 06:26 PM
yatepa yatepa is offline
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Location: Loveland, Colorado
 
Join Date: Feb 2016
Posts: 10
Mein Auto: 1995 540i
Ok, so I am barking up the wrong tree, after I searched the part number on that case, that component does appear to be the fan blower control.
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  #8  
Old 04-11-2017, 09:06 PM
yatepa yatepa is offline
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Location: Loveland, Colorado
 
Join Date: Feb 2016
Posts: 10
Mein Auto: 1995 540i
Quote:
Originally Posted by yatepa View Post
Ok, so I am barking up the wrong tree, after I searched the part number on the case, that component does appear to be the fan blower control.
CCM is the one computer under the hood, my mistake.

Tried many configurtations of swapping LKM and RM computers in the back seat, as well as a CCM under the hood.

I've checked all the fuses and my individual relays test good.

The central locking manually never fails or goes out of sync, I don't get immobilized, and I can trip the alarm by disconnecting the black plug from the alarm module under the back seat.

Door switches, hood switch, and gas door latch all test functional.
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