Rover 75 alarm goes off when opening the car

[holybl00d]

Greeting from Portugal!

This is my first post in this forum, which I have been following for a few years already.

I own a 2004 Rover 75 (December) with an annoying problem. Every day, the alarm goes off when I unlock the car (Key fob or key, it doesn't matter). The alarm only starts sounding a few seconds after unlocking the car, it's not immediate. Sometimes, I unlock the car, and the alarm goes off while I am driving. I have to stop the car, lock and unlock it multiple times (sometimes it takes 2 or 3 minutes) until it stops beeping. This has been happening since this last summer when temperatures can go up to 40ºC. This usually happens when the car is parked for more than 1h, otherwise, everything is ok. I have already lubricated all the sensors (doors, bonnet, etc) and this doesn´t fix the problem.

I have recorded a video to show you what happens.

https://youtu.be/plJvgMle-oM

If you pay attention to the video you will notice that the alarm sounds strange...sometimes it sounds normal and in others it's just a sequence of "beeps".

I greatly appreciate any tips you can give me to fix this issue!

Best regards

[Ducati750cc]

I've never had a factory fitted alarm on any of my Rovers, so can't be specific

However, many alarms have a back up battery which is kept charged by the car, the idea being if the car battery goes flat, or battery cables are cut, the car is still protected by the alarm.

When these batteries get past their sell by date all sorts of odd things, similar to what you are experiencing can occur.

Hope someone will be along soon to confirm, or not, if your Rover alarm has a back up battery alarm.


From memory there is a ' sounder ' under the left hand dash which can be a conventional horn with no backup, or a battery backed up sounder, I can't remember it's name, though I think it starts with a 'B'

[Arctic]

Hi Bill.
It's called a BBUS and is in the ECU area, they can go funny if they get wet or are starting to corrode, i think they are only fitted to car with the head washers.

https://the75andztclub.co.uk/forum/s...d.php?t=142955

https://www.the75andztclub.co.uk/for...d.php?t=152009

https://the75andztclub.co.uk/forum/s...d.php?t=252003

[holybl00d]

Hello guys,

Thank you so much for your input. From from what I've read previously in the forum I also found that the BBUS could be the issue. However, I have no idea where to find it nor how to test it! Any ideas?

[Arctic]

Hi Viseu.
You will find the BBUS unit within the same area as the ECU you will need to remove the plenum outer guard & the plenum tray below it.
A

B

C

D

E

Next remove the plenum under tray.
F

G

Then the three scuttle clips be careful use your thumb over the top so they do not shoot off into the oblivion never to be seen again.
H

J

Remove the first three only.
K

L

You can now slide out the under tray.
M

N

O

P

You can just see the horn top right corner in the pic, but your will be a BBUS
q

This is what the BBUS looks like, it is a BMW unit and ones from a BM will fit our cars.
1

2

They can get water damaged and start plating up.
3

4

5

You can see this one as got water logged.
6

When the battery cover is lifted you can see the real extent of the water damage.
7

8

9

10

These batteries were never going to work again.
11

12

13

The water had also damaged the PCB board.
14

15

Your maybe only a little water damaged but you will not know until it is opened up.

[ceedy]

Had this on my sons 1.8T ..


Found water had corroded of the PCB where one battery wire was soldered.
So no backup power .


I cleaned up the board, soldered the wire back on to another connection point on the PCB, coated the PCB in lacquer, resealed the case and its been ok since. luckily didn't need to replace the battery.


C

[holybl00d]

Hello guys,

Once again, I thank you all for your help. Artic, you were such an amazing help, so detailed! I Will follow your steps ASAP! Cheesy, pardon my ignorance, but what is the PCB? I want to check that as well!

[holybl00d]

Oh, another question, can I simply remove the BBUS and leave it off?

[ceedy]

PCB is just short for printed circuit board..

Originally Posted by holybl00d

Hello guys,

Once again, I thank you all for your help. Artic, you were such an amazing help, so detailed! I Will follow your steps ASAP! Cheesy, pardon my ignorance, but what is the PCB? I want to check that as well!

[Arctic]

Hi Viseu.
The PCB is the electronics green board in the photo below.
1

You can remove it but there is more work to do that, has a working BBUS removed in the wrong way will start going off and will not stop until the internal batteries run out.

One of the links may have this information