Just trying to investigate cause of an older UPS that smells like burning plastic.

Is it likely to be the electric socket, the cooling system of the UPS, or has the unit faulted? If so, what causes these faults, such that I can prevent my office from stinking in the future?

How should I determine if this unit ever trustworthy again?

  • 5
    Throw it away. Buy a new one. Don't even think about trying to repair the damn thing. It's not worth it. Jun 15, 2011 at 16:02

4 Answers 4


Unless this unit is made of solid gold, or cost a TON of cash I would just toss it and buy a new one. Easiest way to test the socket is to put a different ups in place and see what happens.

  • 2
    That's potentially the most expensive way to test the socket too :p.
    – Incognito
    Jun 15, 2011 at 14:22
  • True that, I'd probably just put a different ups, not necessarily a new one, in place for testing. Jun 15, 2011 at 14:40

I'd switch this off and leave it until the manufacturer has inspected it properly - seriously, you don't mess about with dangerous stuff like that dude :)

  • Agreed. UPSes can do some nasty stuff. I once had a 2U rack-mount unit's batteries explode in the middle of the night, dripping caustic goo down the front of a rack. So yeah, pitch it and save yourself a brutal morning.
    – MrTuttle
    Jun 15, 2011 at 17:02

Yes, replace the unit ASAP, do not leave it plugged in overnight as it might start a nice little fire when no-one is looking.


Unless it is a massive commercial ( many thousands of dollars ) unit, then it has no cooling system. If you think the plastic may be burning, then take the unit apart and look for burnt plastic.

If it is bad enough that you can smell it from across the room though, then it is probably best to just replace the unit.

  • 1
    -1 for recommending taking the UPS apart with no safety warning. Taking a UPS apart can be lethal if you don't know what you are doing. See: upsystems-inc.com/papers/maintenance.pdf though I would just recommend replacing it.
    – dr jimbob
    Jun 15, 2011 at 18:34
  • 1
    Not unless it is a massive commercial unit. Your typical SOHO < 1KVA unit runs on a 12v battery, and I assume you're not so brain dead as to leave it switched on while you open it up.
    – psusi
    Jun 15, 2011 at 19:21
  • Many of the professional but small UPSes can have their batteries replaced while they are plugged in (like APC SmartUPS units) - but if it is smelling like burnt plastic, I wouldn't dare pull the batteries out. Better to replace it entirely.
    – Mei
    Oct 31, 2011 at 14:45
  • I have 2 mid-sized APC UPSes (700 Watt and 540 watt) and both have a cooling system.
    – Leolo
    Dec 2, 2012 at 18:53

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