Hi Guys,

Just installing a new alarm control unit as the old one kept throwing up false alarms.

This is going to sound like a really dumb Q but how exactly do PIR's function - I assumed that when tripped they went open circuit to trip the alarm - contacts are marked N/C which I took to be normally closed. Basically the PIR's aren't tripping the alarm, tho' the red light comes on on the PIR to indicate it's picked you up - when I check the resistance across the blue & yellow wires (the circuit I'm expecting to go open circuit) the resistance remains at zero even with someone jumping up & down in front of the PIR & the red light on the PIR permanently on - both PIR's appear to be doing exactly the same thing, would be a bit coincidental if they had both packed up in exactly the same way at the same time!!!

Any info much appreciated?

Have you disconnected the wires from the N/C contacts, there may be a short on the cable.

Scott

[Edited on 18/12/10 by s6otty]

yes it's exactly the same whether you test at the PIR or the control panel, with or without wires connected

quote:

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Originally posted by russbost
yes it's exactly the same whether you test at the PIR or the control panel, with or without wires connected

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They are the original sensors that I fitted with the alarm about 10 years ago, not sure of the make, (alarm box says A1) the weird thing is I know the lounge one was working a week ago as I accidentally triggered it, but when I've connected up to the new control panel everything works except the 2 PIR's - both systems use 12V so it's not that anything has gone over voltage. I've now completely disconnectd the PIR & with just the 12V feed wires attached it puts the led on but there is no open circuit condition across the n/c pins - I can only conclude it's chosen this moment in time to expire - I had suspected the other PIR may not have been working for some time, so not over surprised about that one.
Is it a common thing for them to permanently latch closed?

Normally they just die, but it is possible.

I'd say you've had you money out of them at 10 Years!

Scott

Just a thought, have you tested them at the panel end with the covers fitted to the PIR's?

Im wondering if they wont function while they are in tamper (no covers on)

Scott

Yes that's how I was testing them to start with, when I discovered they weren't working.

Guess I'll just order a couple of new ones, they're not dear on Ebay!