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darbon 27-01-2019 13:51

Alarm sounds off but won't stop with key fob
My lads ZR160 (04 plate) alarm started to sound off without warning last night and wouldn't turn off nor open the door with the fob (all has been OK with the car as he used it yesterday afternoon and regularly for commuting to work).

Tried various thing (removing fuses, changing battery in the pektron fob, resetting it) but all to no avail - alarm still sounding and no response from the car at all.

Disconnected the battery and left it off all night. Went to it earlier this morning and found (in daylight) that one of the leads from the battery to chassis had come away!

Repaired it and re-attached it to a cleaned area on the chassis, put brand new 500cca battery in to car - connected up and alarm sounds straight away and keeps going - cannot turn it off with either of the 2 fobs!!

Any suggestions as to what we can do next will be gratefully received!!!

ps Battery has been disconnected again for now.

Man in the Car 27-01-2019 20:06

Firstly, just to verify whether it is the alarm sounder/siren (mounted on the bulkhead just to the right of the expansion tank) that is sounding continuously, or the horn?

The horn sounding continuously is almost always due to a failed i/c in the Pektron SCU, and it is usually necessary to disconnect the battery or remove the horn fuse to shut it up. Obviously, you then need to remove the SCU from behind the air con evaporator at the back of the dash centre console, with is a bit of a challenge in itself! The SCU can then be repaired (contact Paul Brown at For more information on the Pektron SCU, I would recommend a read of this thread over on

If it is the alarm siren, then it is likely that either the sounder unit has become water logged and needs to be dried out or replaced (the security shear bolts holding the guard casing over it can usually be removed with careful use of Mole grips); or there is a short in the wiring between the body and the tailgate - the wiring frequently gets chafed where it passes through the rubber boot at top right of the tailgate opening. Pull the boot back and thoroughly check these wires and repair if needed.

The alarm sounder has its own back-up battery within the sounder unit, and once triggered will continue to sound and will not normally stop if the main car battery is disconnected.

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