Replacing External Bell Box on Honeywell Accenta G3/G4?

[bigi]

So I’ve tried the suggestion and still no dice.
I’ve tried with and without the scb jumper in place - when out the A terminal allows 13v out across bell+ and itself. But only when the alarm is triggered does the bell- or strobe- output 13v between bell+ and their terminals.

Anything else I can try as this is wired exactly as suggested?

 

[homesecurity]

Fair play to you for helping your elderly neighbour out. Classic Accenta G3/G4 and modern universal SAB sounder mismatch is very common on these older systems.
Here is the physical wiring reality of what is happening:
Your old 30-year-old bell was likely a passive sounder (only powered when the panel went into alarm), whereas the Challenger AU1000WBX is a modern Self-Actuating Bell (SAB) with its own internal NiMH/NiCd backup battery.
A modern SAB sounder requires a permanent "hold-off" power supply (constant 12V-13V) to keep its internal battery charged and hold off the internal sounder trigger. If that hold-off voltage drops, or if the Tamper loop is broken, the sounder's onboard electronics assume an intruder has cut the cable outside, and it fires the siren from its internal battery (which explains why it triggers after a 2-minute delay with the panel disarmed).
Here is the correct terminal configuration between the Accenta G3 board and the Challenger AU1000WBX:
1. Permanent Hold-Off Power:
- Panel [13V+] (or Aux+) -> Bell Box [12V+] (Hold-off positive)
- Panel [0V] (or Aux-) -> Bell Box [12V-] / [Hold-Off -]
Do not take permanent power from Bell+/- terminals on an Accenta; those are switched outpu
2. Trigger Signals:
- Panel [Bell-] -> Bell Box [Trig-] / [Siren-]
- Panel [Strobe-] -> Bell Box [Strb-]
The Accenta switches the negative rail to 0V (open-collector transistor) when the alarm soun
3. The Jumper Setting (Crucial):
Check the jumper pins on the AU1000WBX PCB. Most universal bell boxes have a jumper for Trigger Polarity:
- Set it to "Negative Applied" (sometimes marked "Trig -" or "- Applied").
Do NOT set it to "Negative Removed" or "Positive Applied". With Negative Applied, Bell- sits floating/high at rest, and only pulls down to 0V when the alarm activates. You do not need any 47k resistor pull-up trickery on an Accen
4. The Tamper Loop (The 2-Minute Mystery Siren):
The reason the siren is triggering after 2 minutes is almost certainly the Tamper Return or back-tamper switch.
- On the AU1000WBX, ensure the spring-loaded wall tamper switch at the back is fully depressed against the masonry (or jumpered out temporarily on the bench while testing).
- Connect the Bell Box [Tamper] / [RTN] terminal back to the [T] or [Tamper] terminal on the Accenta panel. If you don't connect the tamper return, or if the microswitch isn't clicking firmly shut against the wall, the SAB timer expires and sounds the ala
Check those jumper pins for Negative Applied and check the rear wall tamper switch, and it should settle down nicely without replacing the panel.rm.ta.ds.ts.

 

[bigi]

Thank you for that great reply; I was actually up the ladder when you sent it so great timing! There were two issues that were causing the problem; firstly I hadn’t tied run- to 0v in the box, so it was going off after the 2 mins delay. Secondly the screw on the outer cover which triggers the tamper switch was not closing - seems a bit on the short side to get to it tbh; although it’s hitting uneven bricks at the back. A bit of carefully manipulation of the actuating bar managed to get it to trigger when screwed In.
The other thing I hadn’t done is handling the scb on the accenta properly; I’d tried with the shorting link across TA and using the aux 13v rails to power the hold off on the box (which I guess is valid); but I’d also tried removing the link when wiring in A for the 0v supply - previously the alarm was indeed connected to a dumb box with a manual siren and strobe bulb. Wiring as you suggested - but with a jumper between trig- and strb- so I could use the spare wire to add the rtn- means that now the alarm triggers as expected and disarms as expected; power remains on at all times and if the box is opened or faulty the spanner icon appears on the control panel (which it didn’t do before). One very happy neighbour, and one very relieved me!

Thank you for all the advice and help from everyone; nice to be able to pass the knowledge around to help others!