Coolant level sensor
 

Changed my expansion tank today, I removed the level sensor from the old tank and fitted it to the new and now I have the 'low coolant, stop engine' message.
I've rechecked the electrical plug and it seems to be right in but still the same so
I guess I need to check the sensor for continuity etc.
Anyone know what I should be looking for - is it circuit continuity or impedance I need to check ?

Did you replace with a genuine Volvo tank?
There are cases where aftermarket tanks interfere with the correct operation of the sensor.

When I changed my tank with genuine Volvo, everything was plug and play.

Not a Volvo tank, it's a Hella. All looks the same and sensor clipped right in, I think I'll put the old one back on tomorrow and see if the message goes away, that will prove one way or the other. Reason for the change is a tiny split near the filler cap, not loosing coolant but saw a bubble when I opened the bonnet after a run.

Sensible move.
You don't have to drain the system to test the theory, just plug the hose holes on the old tank, fill with water and plug in the sensor. :thumbs_up:

Maybe kick the float with a pencil, may got stuck. This sensor is very sensitive if the wire gets pulled even slightly - in particular when lifting a reservoir to work on belts, etc (however this shouldn't be an issue when installing a new sensor)

I fitted a Hella one a few months ago and it works without issue. As above, it could be the float is stuck / sticky?

Sensor works fine in the original tank so that's gone back on for now.
Float is free in the Hella tank, I tried moving the sensor down a bit to see if there was a slight difference in level between the two tanks but didn't find a position where it worked.
Think I'll get a Volvo tank and be sure of it.

Used genuine should be fine (keep the old sensor for spare). Mostly the cap can go bad