I do not have a DX-8, but if I had to guess, I think the problem is that there is a default switch/knob/... assignment to Aux2 that is forcing a value of -100 or +100 and, hence, you cannot get "0" for Off. You should be able to verify the output value via the monitor screen, or plug a servo into Aux2 temporarily.
Verify the assignment of controls to channels and see if this is the issue because that is the only interfering / side effect that has caused this problem for others.
Once you remove the default assignment and have your Guardian mode switch assigned, verify with the monitor screen and, if you now get 0 in the Off position, the Guardian should disable flight stabilization (unlit LED.)
Originally Posted by stevo1957
I installed a Guardian unit tonight but despite having the mode wire in the Aux 2 channel and the flight mode switch in my DX8 assigned to Aux 2, can not get the Guardian to turn off with the switch in the centre position.