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jimleo
February 22nd, 2007, 08:50 AM
I have an Ademco 4150 and last week the alarm horn (in the attic) stopped working. When I trigger the alarm by opening a door, I hear a click from the alarm box, but the horn never sounds. Using the test buttons has the same result.

At the alarm box, I disconnected the wires to the horn and applied 6 volts, and the horn sounds so I know that from the box to the horn the wiring is good and the horn itself is good. Something in the box seems to have failed.
I haven't removed the cardboard cover off the circuit board to check further yet.

Is there a replaceable relay in the alarm box that could have failed? Any other suggestions. Or is it time to get a new system?
Thanks for any help.
Jimleo
suemarkp
February 22nd, 2007, 07:14 PM
If you hear a click, that is probably the relay working. Check to see if it has a fuse in the alarm box. That could have blown.
jimleo
February 23rd, 2007, 01:28 PM
There are 2 fuses. I couldn't tell if they were blown without removing them. I'll check that next.
JimLeo
jimleo
February 24th, 2007, 08:52 AM
The fuses look ok and if I short across connections there still is no alarm. Any other ideas?
suemarkp
February 24th, 2007, 11:31 AM
You need a volt meter next. Is voltage (is it 6 or 12?) being applied to the horn wires when the alarm activates the horn? Disconnect the horn and just put a meter there. If you have voltage, but it won't run the horn, then you have a poor or high resistance connection somewhere or the alarm doesn't have the power to drive that horn.

If there is no voltage, look upstream if you can follow the traces or wires and find its relay. Perhaps the relay is bad and needs to be replaced. It is certaily possible that the relay click when activated, but its internal connections to the contacts that drive the horn have melted or failed. The contacts could also just have a high resistance which is one of the solutions for the paragraph above. You can tell this by measuring the volage across the contacts. With no horn signal commanded, you'll have system voltage (6 or 12) across the relay contacts. When it activates, that voltage should drop to 0. If it is 2V, 3V, or higher, the resistance is high and limiting the current available to the horn.