#114 Repairing a 2 year old Waco day night switch

Recently I had a Waco day night switch start to show faulty signs. Namely once dusk came the relay in the device would oscillate very fast for a few seconds effectively switching the light on/off very fast making a racket while stressing the LEDs out.

The relay would finally settle… mostly on the ON setting but sometimes it would settle on the OFF position. Then if you slightly bang the relay it would oscillate and settle on the ON position.

So I removed the switch and notices there was a lot of spider webs and critters close to the external AC connections. I cleaned the outer case and also notices a brown burn mark where the relay was located. This was due to sparks from the constant ON/OFF switching since the relay in this module had no cover.

Now technically I did not have to open the module but I wanted to see if anything else was damaged. I opened the module and everything looked good except for the relay contacts which looked a bit beat up but were working ok..

I noticed that a resistor and a varistor were very close to the relay and could technically jam it’s opening/closing capability so I moved then away from the contacts and put everything back together again.

I now tested the module again and voila there is no more oscillations. So the grimy critters on top of the AC leads and the resister MOV combo close to the relay contacts were the likely culprits however my money is on the latter. So on re-installing I added extra tape and some silicon to seal the AC terminal blocks completely. A thin layer of silicone can still easily be removed for further maintenance and/or repair.