Relay/controller issues

[Zingiberofficinale]

Hi Folks,

Apologies if this is a numpty question.

I am designing what I thought was a simple circuit to turn on an irrigation pump when a solar controller calls for demand.

Diagram attached (excuse glare).

The solar controller (that also houses a pump which is too small for my needs) is an Irrigatia C24L. It is not clear what the switching current is, but it takes 3x AA rechargeable batteries.
https://shop.irrigatia.com/irrigation-kits/c24-l-series?_gl=1*1xdlj1t*_up*MQ..*_gs*MQ..&gclid=CjwKCAjwi-DBBhA5EiwAXOHsGYY8MuKehycKFuhcFiHzDDhkjq4DFRR0gmGB1AshLuIpKYcX9vErLRoChdoQAvD_BwE&gbraid=0AAAAAqyKR90HHGDn-02zJdiQIUkD6rSli

Transformer is 240v AC to 12V DC supplied to switch (working fine)

The switch is a SP 3 Position Double Throw Cam Switch, 10A (tested and working fine)- https://uk.rs-online.com/web/p/cam-switches/0340291

Switch has three positions (ON - live to 12v pump; OFF; Auto - NO Solar controller on/off).

I have tested the circuit with a spare relay I had (coil could be switched by 9-12v or higher). I triggered the circuit with a variable 3-12v DC supply I have (relay coil only operated at higher end).

Circuit worked fine, so I looked to buy a lower DC voltage to match the lower voltage from the solar controller (which is two leads + / - approx 3v).

I then looked into options for lower voltage triggers for the relay (charging the coil).

Bought this unit, but made the mistake of not checking the input voltage for the coil (12v). Wired NO/Com for relay output, and DC+, DC- for the trigger/coil side.
https://www.amazon.co.uk/dp/B0D9NKVFH9?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1

Solar controller had insufficient voltage to trigger relay coil.

Double checked circuit using variable 3-12v DC supply I have, worked fine above 9V to trigger coil and relay from NO to closed.

So bought this relay board as it states 3v operating current for coil and should work for my circuit.
https://www.amazon.co.uk/PENGLIN-Module-Optocoupler-Trigger-Expansion/dp/B0BJNPKHDG/ref=cm_cr_arp_d_pl_foot_top?ie=UTF8&th=1

Frustratingly the circuit does not work, no matter what combination of connections I try.

Looking at the diagrams associated with the relay:

Relay board output, has a common (-), plus either a NO or NC connection. This makes sense and seems to apply to the switching side of the circuit (connected to pump).

The inputs for the relay board are labelled, VCC, IN, GND.

My reading of documents (pictures on website link above) is that the VCC is the positive (+ from solar controller); GND (- from solar controller).

Have also tried VCC (+ from solar controller); IN (- from solar controller).

Have also tried manually switching relay coil using variable 3-12v DC supply, no success!

Is there a way to utilise this relay board (or similar ones) to run at lower (3V DC)?

What am I doing wrong.

Or is there a better alternative means to take a 3v switching current from the solar controller (NO) to turn on the pump?

Thanks in advance

Mark