I have connected the heater flapper boxes and the cables together
when the lever is pulled up the flap opens, or is it closes? but when the handle is released the flapper pulls the handle back down
I am presuming the lever in the up position opens the flapper boxes?
The lever doesnt stay in the up position as the flappers pull it back down again
How should it work please?
Have I installed them incorrectly?

I believe the handle friction can be adjusted so it holds the flappers open. There is a bolt and lock nut

thank you
its time to remove the centre console to wire it up and set the tension then

It is a diverter valve, heat to the interior is normally closed (blocked) when the lever is down, and the dump port is open. Pulling the handle up blocks the dump port and opens the interior port. The valve has two paddles, one for each port, and a spring in between them. The spring acts to keep a measured pressure on the paddles.