Fault-finding guide

CSL DualCom not working? Here's how to diagnose it

If a DualCom that's already fitted has stopped communicating with the monitoring station, it's almost always one of a handful of common causes. This page walks through what to check first, and how to read the unit's own diagnostic tools.

Signal & GSM checksPath-failure simulationNetwork & commissioning faults

Arrange an engineer visit 0800 13 03 999

Installing a new DualCom rather than fixing an existing one? See our DualCom installation guide instead.

Start here

Six common reasons a DualCom stops working

Almost every DualCom fault our engineers see traces back to one of these causes - it's worth checking through them before assuming the unit itself has failed.

Not registered with the monitoring station

The unit is fitted and powered, but was never fully registered against the account at the monitoring station.

Network ports not open

For IP-based communication, the required outbound port isn't open on the site's network, so signals can't get out.

Incorrect serial port connection

The serial cable between the panel and the DualCom is connected to the wrong port, or wired to the wrong pins.

Weak GSM signal

The aerial is picking up a poor signal where it's currently positioned and needs repositioning.

Incorrect commissioning

The unit was never commissioned correctly against the panel and monitoring platform in the first place.

Channel disconnection

The LAN or internet connection the unit relies on for one of its paths is currently down.

Already checked the basics?

If your DualCom is still not communicating after checking these, our engineers can diagnose it remotely or on site.

Get help now 0800 13 03 999

Weak signal

Checking and improving GSM signal strength

A weak GSM signal is one of the most common reasons a DualCom struggles to stay connected. There are two ways to check it, and a few simple things that usually improve it.

Check the reading
Use the My Base app, or toggle DIP switch 4 on the unit to view the GSM 1 / GSM 2 signal strength on its display, on a 1-10 scale representing 10%-100%. A reading under 3 (30%) means the aerial needs repositioning.
Avoid coiled cable
Excess aerial cable left coiled up degrades reception - keep it as straight and as short as practical.
Keep clear of other electrics
Other electrical equipment nearby can interfere with the aerial's reception.
Reposition it
Try relocating the aerial to a higher point, or nearer a window or external wall, where reception is typically stronger.

Good to know

A flashing dot on the display means the DualCom Pro is actively transmitting data - that's a normal, healthy sign, not a fault.

All current DualCom Pro variants include roaming 4G SIMs as standard, so coverage isn't tied to a single mobile network.

Still not working?

Call our support team

If you've been through the checks above and your DualCom still isn't communicating with the monitoring station, it's time to get an engineer involved - it could be a registration, commissioning or connection issue that needs resolving at the unit itself. AMCO's engineers work with CSL DualCom signalling on a daily basis and can diagnose the fault and get you communicating again.

Arrange an engineer visit 0800 13 03 999

What our engineers check on site

Registration against the monitoring station account
Serial connection and commissioning against the panel
Network ports and LAN/internet connectivity
GSM signal strength and aerial positioning

Want to see what customers who've used AMCO's support team have said? Visit what our customers say.

Not confident diagnosing it yourself?

Send us a photo of the DualCom's display and a description of the fault, and we'll advise on next steps before booking an engineer.

Ask AMCO 0800 13 03 999

Radio & path diagnostics

Radio path troubleshooting reference

Denser, engineer-level detail on the DualCom's built-in diagnostic menus and signal tools - useful if you're already comfortable working with the unit's keypad.

Menu N simulates a primary-path failure and Menu O simulates a secondary-path failure. Use the A/B buttons to scroll through the menu items until you reach the one you want, hold the C button, use A/B to toggle between Yes and No, then press C again to confirm your selection. Selecting “Y” fails that path for a maximum of 15 minutes - this is a deliberate test window, not a real fault, and is mainly useful for engineers checking that failover behaviour works as expected.

Avoid coiling the aerial cable, as excess coiled cable degrades reception. Keep the aerial away from other electrical equipment, which can interfere with the signal. It's also worth trying to relocate the aerial to a higher point, or nearer a window or external wall, where reception tends to be stronger.

You can check it remotely using the My Base app, or toggle DIP switch 4 on the unit itself to view the GSM 1 / GSM 2 signal strength directly on its display, on a 1-10 scale representing 10%-100%. A reading under 3 (30%) means the aerial needs repositioning.

It shows the DualCom Pro is actively transmitting data. It's a normal, healthy sign of the unit working as intended, not an indication of a fault.

Yes - all current DualCom Pro variants include roaming 4G SIMs as standard, so the unit isn't tied to a single mobile network's coverage.

Still not working?

Call our support team

If your DualCom won't communicate after working through this guide, get in touch and we'll arrange an engineer to diagnose and fix it. Fitting a brand new unit instead? See our installation guide.

Arrange an engineer visit enquiry@amco999.com

Free, no-obligation quote

Get your free AMCO security quote

Tell us a little about what you'd like to protect and a member of our family-run team will be in touch - no pressure, no jargon.

Most quotes sorted in minutes by phone
SSAIB accredited · 100% insurance compliant
Spring offer: up to £100 off installation

Call us free0800 13 03 999 Email usenquiry@amco999.com

Covering England, Scotland & Wales