V70: Electrical - Random Alarm activations

ShadeTek · Feb 28th, 2021, 18:02

My car, after coming back from the supermarket, started to randomly chirp. The alarm module sounder would chirp seven times then the main horn would start blaring out. Checked for stored codes-nothing of course which deepens the mystery of the activation cause. After reading up on the alarm the main horn only sounds when it detects the siren module under the wing is not present. I was also getting a message on the dim that read something like "please put the remote key to the rear reader"?...which I have never seen before and means nothing to me.

"If the alarm system indicates break-in normally the Central electronic module (CEM) shall request activation of siren control module (SCM). If this cannot be done due to, e.g., disconnected siren control module (SCM), then the Central electronic module (CEM) activates the normal horn instead as replacement of siren control module (SCM)."

This is a replacement module I got last year from a scrappy which I now suspect has a failing battery. My own module which I still had and replaced the batteries in subsequently suffered water ingress and then started to randomly go off. Now the green crusties are removed and dried out, properly sealed this time it is back on the car and let's hope I don't get the alarm going off early in the morning.

MDSurrey · Nov 3rd, 2021, 05:45

Winter is here and my V70 alarm goes off on cold nights. I thought removing the fuse would work till I got around to repairing it, but as your thread explained, now the bloody horn goes off in the middle of the night which is much worse!!

My question is what part I need to get for the 2008 model V70 I saw a lot of videos online, but all of them seem to work on cars up to the 2007 model year. And I am pretty sure the alarms are different. I am going to try getting something off of eBay, replace the battery and then stick that back in.

Any advice on what to look for?

Tatsfield · Nov 3rd, 2021, 12:16

This fault is very often a failing back up battery in the siren unit. There are thread on this forum about now to buy a battery and replace it yourself which is a lot cheaper than buying a whole siren unit just to have a new battery. I think there is also a video on YouTube.

ShadeTek · Nov 6th, 2021, 10:22

Quote:

Originally Posted by MDSurrey

Any advice on what to look for?

I would remove the module from your car and then if it is the later type module then break it open, they are well sealed, and see if it is saveable by replacing the cells. Mine were two AAA cells if I recall. You can always search for the exact part number on eBay but if it is the same age then it too as I found will suffer cell failure. Also some alarm modules don't have the tilt sensor on board so get the correct part number and not one that just looks like it. They fit these to Fords, Jags etc. Pretty much an off the shelf design.

ShadeTek · Nov 6th, 2021, 19:03

Here is the pcb of the later type alarm with green crusties on the battery leg.

Feb 28th, 2021, 18:02	#1
ShadeTek Premier Member Last Online: Apr 9th, 2024 19:03 Join Date: Dec 2002 Location: Renfrewshire View Photos By: ShadeTek	Random Alarm activations My car, after coming back from the supermarket, started to randomly chirp. The alarm module sounder would chirp seven times then the main horn would start blaring out. Checked for stored codes-nothing of course which deepens the mystery of the activation cause. After reading up on the alarm the main horn only sounds when it detects the siren module under the wing is not present. I was also getting a message on the dim that read something like "please put the remote key to the rear reader"?...which I have never seen before and means nothing to me. "If the alarm system indicates break-in normally the Central electronic module (CEM) shall request activation of siren control module (SCM). If this cannot be done due to, e.g., disconnected siren control module (SCM), then the Central electronic module (CEM) activates the normal horn instead as replacement of siren control module (SCM)." This is a replacement module I got last year from a scrappy which I now suspect has a failing battery. My own module which I still had and replaced the batteries in subsequently suffered water ingress and then started to randomly go off. Now the green crusties are removed and dried out, properly sealed this time it is back on the car and let's hope I don't get the alarm going off early in the morning. __________________ Tek-Emo Villis Emo Bis V70 SE NAV 1.6 D2 2015MY POWERSHIFT, D4162T, 86000miles, RED. /VOL FCR/PEPER OBD2/Acron 9135 OBD2/L.E.D Flasher/VDASH/ANCEL BA301 Last edited by ShadeTek; Feb 28th, 2021 at 18:39.

Nov 3rd, 2021, 05:45	#2
MDSurrey New Member Last Online: Jun 9th, 2022 10:18 Join Date: Jul 2020 Location: Leatherhead	2008 V70 : Alarm goes off Winter is here and my V70 alarm goes off on cold nights. I thought removing the fuse would work till I got around to repairing it, but as your thread explained, now the bloody horn goes off in the middle of the night which is much worse!! My question is what part I need to get for the 2008 model V70 I saw a lot of videos online, but all of them seem to work on cars up to the 2007 model year. And I am pretty sure the alarms are different. I am going to try getting something off of eBay, replace the battery and then stick that back in. Any advice on what to look for?

Nov 3rd, 2021, 12:16	#3
Tatsfield Premier Member Last Online: Yesterday 10:10 Join Date: Nov 2015 Location: Poole	This fault is very often a failing back up battery in the siren unit. There are thread on this forum about now to buy a battery and replace it yourself which is a lot cheaper than buying a whole siren unit just to have a new battery. I think there is also a video on YouTube. __________________ 2012 XC70 SE Lux Polestar 230 bhp D5 Auto Oyster Grey

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