My Denford Triac with Fanuc OM control has developed a Tool changer fault today, when tool changing the carousel goes past the tool pocket requested and keeps spinning until it times out.

I have adjusted the sensor that makes contact with geneva wheel and put multimeter on the block that the sensor is connected to, I get 0 then 5v(or just under) repeatedly as the wheel turns.

If I use the manual ATC rotate buttons on the control, the wheel turns twice and indexes round one position but if I request an T# M6 within a program or MDI it just spins round.

Anyone got any idea what the problem might be?