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Discussion Starter #1 (Edited)
Hi Guys,

I've just brought a 1994 BMW 525 Touring TDS from my partners father so i've known the car and its history for 2 or 3 years but need some advise.

Since he's owned it the reverse parking sensors havent worked, i've opened the boot up and the wiring seems to be part of the cars loom so i assume its a factory fitted sensor system.

When i place the car into reverse the system makes no sounds at all, i've read on the internet it goes through the original BMW stereo...is this correct? I ask because the head unit has been replaced for a fancy Pioneer one.

If not is there anywhere i can start in fault finding and getting the system going.

Thanks, Steve.
 

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Discussion Starter #3
Yep forgot to say that i've checked the fuse in the engine bay (its the only one I can fine) and that's fine.

I've also placed the car into reverse and listened for a clicking as posts i've found on here suggested that if they click then they are working. Each sensor makes a clicking so I assume each one works.

I've tried tracing the sensor wires but its confusing as they appear to end up going into the main loom.

In the boot on the off side i've found what looks like a speaker and two relays...I wasn't sure if that was the reverse sensors or maybe a buzzer for the towbar? Next to these is also a socket with two wires connected to nothing but the wire that plugs into this also fits (same electrical fitting).

I'm guessing if the sensors click then the system would be active and ready.

Does anyone know if the beeping is usually produced through the car speakers or an independent speaker like that in the boot?

Most control boxes in the car are either BMW or Siemens/Motorola marked - it had a pphone kit.

I can post pictures if they will be of any help.

Thanks, Steve.
 

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Discussion Starter #5
Yeah it looks alot like that - atleast there are components like that in the car.

The box labelled #1 is on the near side in the boot behind the panels, 4 reverse sensors in the boot (that do click) and a speaker that looks like #12 is on the off side in the boot behind the panel.

The wire that clips onto the speaker also is the same fitting as what fits another wire in that area - basically there is a two core wire with the same socket as whats on the speaker but nothings plugged into that. There are also 2 of what I presume are relays, both near the speaker.

If the sensors click would that indicate that box #1 is functioning and maybe its just a broken speaker? Would it be wise to put a multimeter onto the speaker wire?

Regards, Steve.
 

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You could try a test light or multimeter, in theory a test light may be better, it should flash I would think
 

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Discussion Starter #7
Hey,

Just been out to the car and checked, tested a lamp on the side lights and worked fine (just to make sure) but when I connected it to the two wires nothing appeared to happen.

Could this mean that the fault is with the control box? I've unplugged wires from the control box and the sensors stopped ticking so I believe I am looking at the correct box.

Regards, Steve.
 

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On the later models the parking sensors work through the stereo, I can't for the life of me recall how the sound is transmitted on a e34, I'm not even sure if a diagnostic will get to the bottom of the problem, Later PDC systems can have the ECU read, As yours has a factory fit system it will probably be worth pursing checking for codes.

I'm going to stick my neck out and say it's the stereo install that has disabled it though.
 

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Discussion Starter #9
Yeah the stereo was something mentioned on other sites but wasn't sure. A previous owner has also cut half the wires behind the stereo before the ISO (i think) and reconnected with bullet connectors.

I've got an mp3 player lead to install onto the stereo later so I'll have another look.

If it is the stereo that has switched it off does that mean it'd never work with the stereo thats there?

Tempted to just buy a kit off ebay and wire that up, swap the sensors and have an independant one. Just would have been nice to get that one working but never mind :)

Thanks for all your help.

Regards, Steve.
 
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