Set Square wrote on Saturday (14/02/2004) :
Ed wrote:


The spring return is smooth and fast, no problems there. As I write
the system is behaving fine so it's a little hard to do diagnosis.
When I did the wiring checks I did find one wire in the connection
unit that could have been tighter but really didn't seem loose enough
to be a troublemaker. I've given it a little tweak anyway so now I
just have to wait for the next cold morning. Still baffelled by the
way it sits on AB with ALL wires disconnected, what is holding it
there? If you pull the power at the FCU it spring returns sharply...
Watch this space...

If it is a Sunvic valve actuator, it is a well known problem...

The two positions away from the 'home' position are held by constantly
cycling the motor on and off against the spring.....
The motor runs until the microswitch controlling the motor is opened by
the cam, the spring causes it to back off a little, microswitch closes,
motor runs again until the switch opens.

Sometimes the mechanisms sticks, with the spring unable to return the
valve to the home position. Undo the two screws when the valve is
stuck, and it will likely then go to its correct position. Sometimes
just knocking the actuator is enough to make it return.

The long term solution is to replace the valve with new, about £45-ish.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org