What is the OBC relay for?

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jimf
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Post Thu Jun 04, 2015 9:06 pm

Sorry this is a bit of a re-post but the question is different.

Is the OBC relay designed to take the place of the alarm control unit on cars that don't have a factory fitted alarm?
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Brianmoooore
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Post Thu Jun 04, 2015 11:17 pm

Yes, but the alarm/immobiliser is the one that has the second keyhole for a magnetic key fitted into the door, not the more common one operated by a remote fob.
The black relay box is largely empty space, with a couple of small relays in one corner.
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jimf
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Post Fri Jun 05, 2015 5:38 am

Thanks Brian. I'm starting to get somewhere with this. It seems, to have the MPG, range, time and temp (the only ones anyone uses) to work you don't need either! So I should be good to go.
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Brianmoooore
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Post Fri Jun 05, 2015 9:52 am

The only functions of the two relays are to control the alarm horn, which should be under the panel in front of the LH front wheel arch, and to immobilise the engine by breaking the ignition feed to it, controlled by the CODE function of the OBC.
As said above, both are close to useless, and there is a known possible issue with the immobiliser relay and its circuit board tracks being a little under specified for their job, which can lead to a misfire.