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Topic: Car Alarm Keeps Sounding (Read 584 times) |
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Technology2005
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Scorpio 2.0 Ultima x 2
Posts: 207
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Car Alarm Keeps Sounding
« on: Mar 11th, 2010, 7:49pm » |
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At random intervals the car alarm keeps sounding on the 96 Ultima 2.0. This car hasn't been used much recently and the battery has gone flat a couple of times whilst it was stood for 5-6 weeks at a time.
*ruddy thing just went off whilst trying to type this up* 
The car has had a couple of good runs this past few days and it has been nice dry weather. The battery cover is in place and the drain holes clear so doubt it's damp in the electrics.
What are the most likely culprits for the false alarms? Do the alarm activations register on the OBD scans?
What is the best method for checking this out? I'd disconnect the horn behind the battery to stop it annoying the neighbours but then it will just keep going off and flattening the battery and I'll be none the wiser until I go to use it!
(I'd rather cure it than kill it !)
Any thoughts....
David
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Simmo
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I'm an OAP !
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Re: Car Alarm Keeps Sounding
« Reply #1 on: Mar 11th, 2010, 7:59pm » |
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Bonnet switch ?. A common cause. 
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Now I'm an OAP
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Technology2005
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Scorpio 2.0 Ultima x 2
Posts: 207
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Re: Car Alarm Keeps Sounding
« Reply #2 on: Mar 11th, 2010, 8:20pm » |
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Might be, is it easy to disconnect the wiring to this? I'm assuming it's the plunger type device in the centre of the front near the bonnect catch with a rubber boot around it?
If I pull the wires off will this stop the alarm sounding until I can check the switch out? I'm guessing the alarm won't arm with the switch disconnected, or will it cause it to go off immediately instead?
thanks,
David
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Technology2005
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Scorpio 2.0 Ultima x 2
Posts: 207
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Re: Car Alarm Keeps Sounding
« Reply #3 on: Mar 11th, 2010, 8:23pm » |
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Oh hang on....found the method to disconnect the bonnet switch so can remove it easy(!) enough.
Should get me through the night.
David
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tonyboy
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black2.924Vcoss ( No More )
  
 
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Re: Car Alarm Keeps Sounding
« Reply #4 on: Mar 11th, 2010, 8:31pm » |
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Hello here's something that might be helpfull if you havn't seen it already............ http://www.fordscorpio.co.uk/alarmsys.htm
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I think i'm going, erm what do you call it..... Senial.... 
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Technology2005
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Scorpio 2.0 Ultima x 2
Posts: 207
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Re: Car Alarm Keeps Sounding
« Reply #5 on: Mar 11th, 2010, 8:36pm » |
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Ahhhh, I was looking for the rest of the alarm system notes,
Thanks, although it looks like testing the switches for functionality could be a pain!
I'll start by bridging the connector to the bonnet switch and see if I get any more false alarms.
David
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tonyboy
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black2.924Vcoss ( No More )
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Re: Car Alarm Keeps Sounding
« Reply #6 on: Mar 11th, 2010, 9:01pm » |
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You might want to check if the switch is normally open, or normally closed.... when the bonnet is shut.....
Should be easy enough to check, connect a multi meter across the 2 wires that come from the switch and check the resistance when you press down the bonnet switch...
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I think i'm going, erm what do you call it..... Senial....
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Technology2005
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Scorpio 2.0 Ultima x 2
Posts: 207
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Re: Car Alarm Keeps Sounding
« Reply #7 on: Mar 11th, 2010, 9:17pm » |
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Yep, understand that....I'll be interested to see if it responds to being moved too.
Typically, the alarm has decided to be quiet for now....it's just waiting until I go to bed.... I know it is 
David
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Technology2005
Full Member
Scorpio 2.0 Ultima x 2
Posts: 207
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Re: Car Alarm Keeps Sounding
« Reply #8 on: Mar 12th, 2010, 12:59pm » |
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Well the switch is normally closed when the bonnet is shut as I've just removed it and checked with a multimeter.
The switch seems to be operating normally so the fault may be elsewhere.
Am I right in assuming that with the bonnet switch disconnected that the alarm will not arm (so no "protection" and no false alarms) but that the PATS will still operate?
David
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Mike H
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Renault Clio
Posts: 2594
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Re: Car Alarm Keeps Sounding
« Reply #9 on: Mar 16th, 2010, 8:23pm » |
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I believe so, that was the case with mine when I got it, previous owner said the alarm never worked, all it was the bonnet switch was unplugged (presumably by the dealer he got it off for some reason)
The PATS is a completely separate thing worked by the correct key in the ignition.
Incidentally, re the previous I discovered when you lock the car, if the dashboard LED lights for 5 seconds then won't flash afterward, it's trying to tell you there's an alarm problem.
I believe all this is done by the PCM which is on all the time drawing battery current whether the alarm is activated or not (it's all done by the same computer box I believe). Come to think of it that's probs why the dealer "disabled" it as an attempt to save battery charge (no sorry it ain't that simple!  )
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Mike H
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Mike H
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Renault Clio
Posts: 2594
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Re: Car Alarm Keeps Sounding
« Reply #10 on: Mar 16th, 2010, 8:29pm » |
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Afterthought ~ re your problem I might think in terms of "dirty" door switch contacts, these are alarm loops as well I think so actually the contacts are closed when the doors are shut, I think. The opposite way round to what you normally expect (e.g. if just lighting the interior lights). Could be wrong about that of course but got the idea from somewhere. Anyhow door switches are deffo involved with the alarm.
PS and boot as well of course
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Mike H
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Technology2005
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Scorpio 2.0 Ultima x 2
Posts: 207
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Re: Car Alarm Keeps Sounding
« Reply #11 on: Mar 17th, 2010, 8:08am » |
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Thanks for that Mike, as an update since I removed the bonnet switch a few days ago the alarm has (of course) not activated so I'll have to get round to checking the other switches when I have time.
I'd certainly expect dirty or worn contacts to be the problem given the age of the car but it'll be time consuming to locate and test them so it'll have to wait for now.
Thanks for everyones help
David
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Mike H
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Renault Clio
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Re: Car Alarm Keeps Sounding
« Reply #12 on: Mar 17th, 2010, 11:52am » |
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Try a good squirt of WD40 down each plunger and pushing it a few times. Might work. If I'm right and it's a closed loop I think what might be happening is the contact resistance goes high cos of oxidation etc., hence it's OK for a bit until it "crosses the theshold", and of it goes. Only thing I can think of that matches your one's behaviour. Or nothing more complicated than a bad connector. Again just needs a bit of a clean.
I could equally of course be talking complete cobblers I'm just guessing
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Mike H
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