Gates dont close after being held open

[Blakey111]

Hi, This sounds like an intermittent issue with one of the external devices which has been hard wired into the control panel, I.E. Keypads, proxy reader, intercom, keyswitch etc. I would imagine one of these devices is causing a short to trigger the input on the control panel. Take a look between terminals '17' and '20' on the panel and see if there is anything wired between those 2 terminals. If there is, then there is and external device which has been hard wired into the system. Remove what ever has been wired into these terminals and see if the problem persists. If not then re-apply the devices one by one until the problem replicates to which will identify the problematic device.
(Basically, anything that shorts out terminals '17' and '20' will trigger the gates to operate.

Hope this helps,
Dave

Hi, I have Liftmaster sub 300s with a CB11 control unit and photo cells. When we zap the gates open when in the car the gates behave and close again behind us after the time delay. However, we can hold the gates open by pressing the zapper again once the gates are open. That works. However, if we then press the zapper again after say the visitors have gone, the gates start to misbehave and close and open a few times before returning to the open state. Sometimes they will then close of their own accord half an hour or maybe an hour later. Sometimes they will close if we zap them again after the same sort of length of time.

An independent gate engineer came today to service them and look at the problem. He thought the issue might have been spiders etc in the photocells but no. Even when he disconnected the photocells they misbehaved. I am now being quoted aot of money to change the cb11 to a different model, and the zappers but its outside my budget!

Is there a solution to this problem? What other information do you need to know to advise? Do i need a new board?

Many thanks