Cerbo gx not displaying correct AC input and Output

Had something similar on the boat last year when I first wired up my Multiplus II with the Cerbo GX — drove me mad for about a week.

The AC input and output were just showing dashes on VRM, nothing registering at all. Turned out I'd missed a couple of things:

1. The AC current sensor — make sure you've actually got one fitted if you want proper readings. The Cerbo can't magically know what's flowing without it.
2. VE.Bus configuration in VEConfigure — worth double-checking your assistant settings and that the system type is set correctly. Mine had defaulted to something odd.

Also worth checking:

• Is the RJ45 VE.Bus cable seated properly between the Multiplus and Cerbo? Sounds obvious but mine was ever so slightly loose
• Are you on the latest firmware on both units? Victron pushed a few fixes around this

One thing that catches people out on caravans vs narrowboats — if you're running off a hook-up lead and the Cerbo isn't seeing mains as a valid AC source, it might just be a shore power detection threshold issue in the settings.

What firmware version are you running on the Cerbo? And is this a GX Touch setup or just the VRM portal online?

Would be good to know exactly where it's not displaying — is it the VRM dashboard, the GX Touch screen, or both? Makes a difference in where to start digging.

Others on here will probably have seen this too — anyone else had AC readings drop out on a Multiplus II setup?

@BenJohnson95 classic Victron "it works perfectly, you've just done something wrong" energy 😄

Nine times out of ten it's the VE.Bus cable — either the wrong type, damaged, or someone's used a standard ethernet cable thinking it'll do the job. It won't. Ask me how I know.

Other things worth checking

@BenJohnson95 worth double-checking your VE.Bus cable is properly seated at both ends — sounds obvious but the RJ45 connectors on those Multiplus II units can look fully clicked in without actually making proper contact. Had exactly this on my narrowboat build; Cerbo was seeing the inverter/charger but AC readings were all dashes or wildly incorrect.

Also check the Multiplus II grid code settings via VEConfigure. If the grid code isn't set correctly for your region (UK = EN50549-1 typically), the unit can behave oddly with AC input detection. That's done through a direct laptop connection with the MK3-USB interface — not remotely via VRM.

One more thing: are you on the latest firmware? Cerbo GX firmware mismatches with the Multiplus II firmware have caused this exact symptom. Update both sequentially, Multiplus first.

@BenJohnson95 one thing neither of you have mentioned — check the AC sensor assistant is actually configured in VEConfigure. The Cerbo can't display AC input/output correctly if the Multiplus II isn't reporting it properly over VE.Bus, and that often comes down to whether the grid setpoint and AC current sensor settings are actually written to the unit.

In VEConfigure3, go to the Assistants tab and verify there's no conflicting assistant loaded that might be suppressing the metering data. I had this exact scenario with my shepherd's hut setup — spent ages suspecting the RJ45 before realising I'd loaded an old config file that had the ESS assistant half-configured, which was causing the metering to report zeros rather than live values.

Also worth confirming your VE.Bus firmware is current — older firmware versions have known issues with AC metering data over the Cerbo.

@HelenPhillips makes a good point on the assistant config — that catches people out a lot.

One thing I'd add: check your grid code setting in VEConfigure. If it's set to the wrong country standard the Multiplus can refuse to show AC input properly, especially if it's not "accepting" the grid as valid. Had this exact issue on my garden office install — was set to some random European code, switched it to UK G98 and everything appeared instantly on the Cerbo.

Also worth checking: if you're on shore power on the boat, make sure the input current limit isn't set to zero — that can cause the display to show dashes as if nothing's connected.

What firmware version are you running on the Multiplus? Some older versions had quirks with Cerbo reporting.