My APC UPS - RS800 (bought in India) started clicking after 5 years. As of this writing it's with APC for servicing.
Now read this: It was connected to a good voltage stabilizer for about 4.6 years. I removed the voltage stabilizer thinking that the UPS itself has a built-in stabilizer. The UPS started clicking a month ago. It would click a lot sometimes (like once in 15-30 seconds) and click little (like once in 30 mins). I had replaced the batteries about 8 months ago. The APC service guy dropped in and didn't really have a clue. He kept stressing that if the sensitivity is set to low it wouldn't click. I had a hard time convincing him that the UPS must not click with default (factory) setting. I have another new APC UPS (RS1000) which doesn't click at all (regardless of the sensitivity setting).
After doing hours of reading on this issue, I finally concluded that the APC UPS need a good voltage stabilizer. If you don't protect it with a good stabilizer over a period of time (perhaps 4-8 months) the solid state circuitry inside the UPS starts acting up. It just starts malfunctioning.
I strongly suggest you have the APC service take the UPS to their service center and fix it. OR if you think buying a new UPS is cheaper go for it.
Do not use the clicking UPS. The voltage coming out of a clicking UPS could fail your costly electronic gadgets/components/computers/etc., I checked the voltage with the multimeter on my clicking UPS and it was quite high indicating that it's a major problem. I suggest you use a multimeter and check the output voltage at different times on your clicking UPS.
One of my routers stopped working, just went dead. And my mind tells me that it was because of the clicking UPS. Hope all you guys find my detailed feedback on this issue helpful.
All the best.
