Garage door opener remotes do not work when light is on. I have the same issue with three remotes with fresh batteries. Removing the lightbulbs does not help. The wired wall button works fine. The unit is 20+ years old and only started having issues about 2 weeks ago.
1 Answer
I diagnosed and found the large electrolytic capacitor on the circuit board went bad. I removed and replaced the capacitor and it works as good as new.
Details: With a bad capacitor the operating voltage becomes unstable. With the the light bulb solenoid engaged that seems to stress the power circuit even more to the point that the RF system stops working.
The original capacitor was 330uF 35V. I did not have that exact value but I had a bunch of 1500uF 16V capacitors so I put 2 in series to form the equivalent of 750uF 32V. In this case a higher uF is beneficial since its purpose is to smooth the DC voltage produced by the rectifier diodes. The slightly lower voltage rating is fine since the nominal operating voltage is 22V.
See before and after photos of the repair: https://photos.app.goo.gl/NyngpJCpYHafmWB39
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Nice! Amazing how often it's the smoothing cap. Personally I'd order a few 330uF (or 470uF) electrolytics from a known good supplier (i.e. not ebay) in case this goes again...– 2e0byoCommented Oct 21 at 8:24
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4Most definitely acquire new caps. Putting them in series like you did works perfectly only in textbooks, in real life they are bound to fail as the voltage will not split equally. There are ways around this, but the right cap is the best way. Moreover, more cap is not always better: better for smoothing, yes, but e.g. the rectifier diodes will see more inrush current, which might or might not be okay. Commented Oct 21 at 11:52
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6For a 20+ year old opener I'm not sure that stocking up on caps is worthwhile. Plenty of other things can go wrong next and a replacement cap is a day or two from a good supplier (Digikey, Mouser, ...). Commented Oct 21 at 13:36