cb24 photocells

[devonaloan]

I have a CB24 board with photocells. They are set to operate on close only and have been working fine for a couple of years. Now, instead of a consistent red light on the cells, there is an intermittent flash - time between flashes can be between 2 seconds and 40 seconds. Occasionally they will stay on long enough for the timer to run out and will then go off.
This of course means i cannot close the gates. Even removing the photocells from the circuit and shorting the connectors won't allow me to close (can the learning process of the photocells be 'unlearnt'?)
I have checked the batteries (12.5v and 12.7v respectively) and cleaned out the inside of the cells (and evicted spider!) with no luck.

The only oddity i can see is perhaps (and this might be my imagination) that one light is brighter than the other - and the duller one is at the end of the longest cable run.But as i said it has been fine for 2 years - and has worked ok twice today.
Any advice would be appreciated

[Mark]

It could be the cable has degraded over time try replacing the cable.

The Photocells can be unlearnt from the CB24 you need to link out the connector switch save switch to off then unplug the power and the batteries wait 10 seconds reconnect power and batteries wait 20 seconds and then switch save back to on and the red led should now be out and the system will operate without the photocells. However there will be no saftey on this system so it is not advisable to have the gates auto closing or indeed working at all without saftey. But the system will work without the saftey cells.