On 08/04/2026 at 11:27, PeterJames said:

I just spat my tea across my office reading that LOL !

 

I note the OP has not posted since 🙂

1 minute ago, MrHappy said:

 

I note the OP has not posted since 🙂

Alarm men start taking readings like sparkies just make them up

 

On 04/04/2026 at 20:40, MrHappy said:

Do you have a fat wife who waddles across the landing squashing the alarm wire between the floor board & central heating pipes ? - rewire &  book her into slimming world.

Damn boy 🤣🤣

Update to the random tamper problem.

 

Some of the PIR switches had a high ohm reading.

 

I opened up each PIR in the circuit and put an ohm meter across each tamper switch, then closed the switch. Some of the switches read 100s Ohms even with the contacts closed. What I found odd was that repeated pressing of the tamper switch lowered the resistance. I could see it drop with each press. PCB inspection didn't reveal any dry solder joints (sometimes the joints crack) but re-flowed the solder on all switch legs and the contact block just in case while I had the PCB out. Each has a closed resistance of 0.1 Ohms now, so all good and no tamper alarms since.

 

These PIRs were first sold in 85 and I think they had a 10 year run (Honeywell IQ220), so they're between 30 - 40 years old. I know switches need a 'wetting' current to break through the surface film resistance on a contact, so it might have been something to do with that given the time in service. I'll replace all the PIRs if they become a problem, but they're fine at present.

 

Never seen that fault before.

 

MrHappy>When an alarm is fitted by a proper alarm co. they do boring stuff called commissioning ......

 

Also measured the full circuit tamper resistance and left a note in the control panel for future fault finding. A good idea.

 

Thanks for all the replies.

 

Buy sensors with compatible FSL resistors built in if you haven't started already.