# Cerbo gx + webasto + ruuvii **URL:** \ **Category:** DIY\ **Tags:** marine, cerbo\_gx, diy\ **Created:** [7 January 2025 02:13 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788 "2025-01-07T02:13:02Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 02:13 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/1 "2025-01-07T02:13:02Z")
Hi all, Is there any documentation anywhere that talks about how to leverage ruuvii sensors and the cerbo gx relay to control my Webasto heater on my boat? The thermostat is famously inaccurate and I am either frozen or burning up! I am not adept at cerbo programming yet but am willing to learn. Thank you! ---
**Author:** ![alexpescaru](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/alexpescaru/32/270_2.png) [@alexpescaru](https://community.victronenergy.com/u/alexpescaru)\ **Post date:** [7 January 2025 08:38 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/2 "2025-01-07T08:38:45Z")
1. Is your webasto talking W-Bus or you can turn it on through an 12V on/off signal? 2. Do you have Node-Red enabled on your Cerbo? If yes, make a little algorithm there and automate it. ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [7 January 2025 09:59 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/3 "2025-01-07T09:59:09Z")
See the section on setting temperature control of the relay in the manual, link below. I have a temeprature controlled relay and that shows Ruuvi Tags as possible temeprature inputs. [Cerbo GX Manual, temperature control rules](https://www.victronenergy.com/media/pg/Cerbo_GX/en/configuration.html#UUID-9dc9f6e6-dded-085d-1034-e8895aa34131) ---
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 13:17 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/4 "2025-01-07T13:17:16Z")
I’m not sure about w-bus. It is the air top evo 3900. Does this literature help? > **[lit909385b.pdf](https://techwebasto.com/phocadownload/documentation/archive/blueheat/generic/lit909385b.pdf)** > > 1272.44 KB ---
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 13:26 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/5 "2025-01-07T13:26:04Z")
It’s worth noting I have the MC-04 controller… ---
**Author:** ![alexpescaru](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/alexpescaru/32/270_2.png) [@alexpescaru](https://community.victronenergy.com/u/alexpescaru)\ **Post date:** [7 January 2025 14:38 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/6 "2025-01-07T14:38:50Z")
You need to: 1. Configure the Cerbo as @pwfarnell said 2. Connect the Cerbo’s NO relay contacts between pin 2 and 6 of the X7 connector of your Webasto. Pin 6 of X7 connector is the start command pin, but it seems that the current that goes to that pin needs to be limited somehow through a resistor, resistor that already exists on the output from pin 2. ---
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 15:06 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/7 "2025-01-07T15:06:10Z")
Thanks Alex. My understanding is I need to put an automotive relay between (30a) the cerbo and the Webasto because the cerbo only supports 6a load, and the heater fan causes fly back current on the coil. So, cerbo, 30a NO relay, Webasto. ---
**Author:** ![alexpescaru](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/alexpescaru/32/270_2.png) [@alexpescaru](https://community.victronenergy.com/u/alexpescaru)\ **Post date:** [7 January 2025 15:35 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/8 "2025-01-07T15:35:12Z")
You don’t need to connect in the way are you describing… Just take a look at page 29 of your document, when the much simpler Rheostat is used. The S1 button is for starting the Webasto. It connects Webasto’s pin6 with pin2 through an internal resistor. The same must be done with the Cerbo’s relay, leaving in place your MC04 controller. The Cerbo’s relay will act like that push button. ![1](https://europe1.discourse-cdn.com/victron/original/2X/2/211648b058c3f02f35d5080e55853f35a5a9810c.jpeg) ![2](https://europe1.discourse-cdn.com/victron/original/2X/8/8b01c278e625887c384ba20c786e3ef883f5b613.jpeg) ---
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 16:20 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/9 "2025-01-07T16:20:17Z")
Thanks Alex, this makes sense. One other wrinkle I didn’t consider is that the power button on the controller initiates a shutdown sequence for the Webasto to prevent it from “carbing up” for lack of a more scientific term. I’m not sure if the behavior is the same if you use the relay to kill the power? ---
**Author:** ![alexpescaru](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/alexpescaru/32/270_2.png) [@alexpescaru](https://community.victronenergy.com/u/alexpescaru)\ **Post date:** [7 January 2025 16:22 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/10 "2025-01-07T16:22:53Z")
The shutdown sequence is programmed inside Webasto. It’s performed automatically. Button ON - Webasto starts, warm up and work. Button OFF - Webasto performs the clean-up phase, cools down and stops It’s all inside Webasto firmware. Just try it first and play with an external button connected between those two pins. Then later, if you are satisfied, use as button the Cerbo’s relay contacts. ---
**Author:** ![HRTKD](https://avatars.discourse-cdn.com/v4/letter/h/779978/32.png) [@HRTKD](https://community.victronenergy.com/u/HRTKD)\ **Post date:** [7 January 2025 16:41 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/11 "2025-01-07T16:41:42Z")
I have six Bluetooth sensors (Ruuvi and Mopeka) reporting to my Cerbo GX. They’re good but I would be reluctant to use them to activate relays. For my relays that activate warming systems, I use hard wired temperature probes that plug into the Cerbo GX. ---
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 19:11 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/12 "2025-01-07T19:11:29Z")
Thanks Alex, can you help me understand how I splice the cerbo relay wires into these pins in the X9a connector, and which relay wire goes to which pin? (Cerbo NO to ? and Cerbo Common to ?) ---
**Author:** ![Dbsea](https://avatars.discourse-cdn.com/v4/letter/d/eb9ed0/32.png) [@Dbsea](https://community.victronenergy.com/u/Dbsea)\ **Post date:** [7 January 2025 19:12 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/13 "2025-01-07T19:12:21Z")
thanks Jim. where do you plug these probes into, and can you recommend which ones to use? ---
**Author:** ![pwfarnell](https://dub1.discourse-cdn.com/victron/user_avatar/community.victronenergy.com/pwfarnell/32/2341_2.png) [@pwfarnell](https://community.victronenergy.com/u/pwfarnell)\ **Post date:** [7 January 2025 21:41 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/14 "2025-01-07T21:41:14Z")
Victron temperature sensors for the Cerbo GX, just connect it to the temperature sensor inputs and set it up, it is all in the manual. [Cerbo GX temperature sensor](https://www.victronenergy.com/meters-and-sensors/temperature-sensor-qua-pmp-venus-gx) [Cerbo manual section 4.11](https://www.victronenergy.com/media/pg/Cerbo_GX/en/connecting-victron-products.html#UUID-a640216a-127d-5a68-5f89-57eee74066cb) ---
**Author:** ![Nillan](https://avatars.discourse-cdn.com/v4/letter/n/7cd45c/32.png) [@Nillan](https://community.victronenergy.com/u/Nillan)\ **Post date:** [11 February 2025 22:17 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/15 "2025-02-11T22:17:14Z")
Hello there, Im thinking about trying to start my webasto with the cerbo. I noticed your drawing on the schematics. This specific controller consist of 3 items as i see it. 1.A switch(on/off). 2.what you refer to as a resistor is a green led light in the switch. 3. And at least what you have not accounted is the controllers internal variable resistor that is set by the switch position(pin 11 and 08) this also needs to be manipulated by the relay or else the webasto will only start and then shut down pretty fast because that resistance is compared to the air temperature to decide the webasto output. But My conclusion, could be wrong of course. ---
**Author:** ![overlars](https://avatars.discourse-cdn.com/v4/letter/o/85f322/32.png) [@overlars](https://community.victronenergy.com/u/overlars)\ **Post date:** [21 October 2025 08:38 UTC](https://community.victronenergy.com/t/cerbo-gx-webasto-ruuvii/17788/16 "2025-10-21T08:38:28Z")
Has anoyne tried this? I’m looking to test this as the winter is coming but I’m a bit confuced regarding if i have to install an extra relay or not