A Linear Brand GDO (model LD033) does not close unless the wired button is held down.

I believe optical safety sensors:

  1. may have been exposed to flood water (hurricane Matthew flooding)
  2. LEDs are not lit up as per normal ops (all LEDs dark)

UPDATE: LEDS light up: the red LED on photo-detector is dark. Normally it is red when it detects the emitter source.

I suspect that the GDO thinks that the optical safety beam is interrupted \ broken and that is the reason why the RF opener can not close the door.

NORMAL GDO OPS: A separate, asymptomatic, instance of the same GDO setup was exposed to flood water but did not suffer this problem. Observations of normal ops include visible sensor LEDs being lit up to indicate power. Interruption of the beam results in one of the two LEDs going dark (red LED). The symptomatic GDO's unlit \ dark LEDs in the optical safety sensors indicate either the sensors are not receiving power or are damaged.

I would like to isolate (diagnose) the problem for corrective action: is there a good troubleshooting procedure? Any process or diagnostic questions are appreciated

  • Are the GDO sensor emitters on the faulty unit receiving power? Commented Oct 15, 2016 at 16:15
  • @ThreePhaseEel: update: sensor and emitter both lit up and receiving power. Sensor seems stuck in state that signals optical-beam interrupted: tested with a known good emitter.
    – gatorback
    Commented Oct 17, 2016 at 0:17

2 Answers 2


The receiver unit likely shorted out inside from the flooding -- it might be possible to fix it by cleaning the insides thoroughly to get rid of any contamination that'd be causing the short, but it could also be that parts inside it failed. We'd need some photos of its innards to make that determination, though...

  • I like how you think. Will put it under a fan tonight to dry it out (if that is possible). Likely that electronics are damaged from being immersed in water. Will report future test results and open it up if it fails. In all likeliness: will replace it with unit from AMZN.
    – gatorback
    Commented Oct 17, 2016 at 0:48

On the units I have worked on the emitter is usually a 2 wire and the receiver is a 3 wire . I have worked on some that are 12-24v and some that are 120v if there is voltage the emitter would be my first replacement because it should always be lit. The receiver should be lit when it sees the beam from the emitter but they both may have been damaged by the water. I looked at the web site but did not see the sensors listed.

  • Would it make sense to wire-up (and test) the symptomatic sensors in the known-working system or would I risk borking up the good system?
    – gatorback
    Commented Oct 16, 2016 at 17:10
  • They are easy to test if the emitter is not lighting up it is not getting power or is bad, the receiver with power applied the receiver with power applied a bright flash light will usually turn on the output and it will light up. The emitters normally run from 690nm to 1064nm wavelength (red to infared) but a bright light will usually turn them on.
    – Ed Beal
    Commented Oct 16, 2016 at 20:39
  • Emitter and receiver were removed and tested one at a time in a known good system. Transplanted emitter passed test. Photo-detector failed. Unsuccessful attempt to simulate known good photo-detector with MAG-light. Sensors are available on AMZN
    – gatorback
    Commented Oct 17, 2016 at 0:12

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