Capacitor polarity

[Bill PhinnParticipant @billphinn90025]

My 36 year-old Tatung fan has begun to rotate more slowly than usual. I've tried oiling the shaft, but it didn't change much, so I don't think that's where the problem is.

I'd like to test the capacitor with a multimeter, and if necessary buy a replacement. Can anyone tell me, from looking at it, whether the fan's capacitor actually has polarity or whether it is a kind that doesn't? There are no markings indicating polarity on it whatsoever.

[Bill PhinnParticipant @billphinn90025]

[Andrew TinsleyParticipant @andrewtinsley63637]

It isn't an electrolytic capacitor, so you can connect it either way around.

Andrew.

[Anonymous]

Value is a microfarad, rather low for a metal can electrolytic, and the voltage rating is given as 400VAC, so it isn't polarised. The MPP stands for metalized polypropylene, so most likely self-healing.

Andrew

[Howard LewisParticipant @howardlewis46836]

Your local motor rewinder should be able to supply a replacement fairly cheaply. Just take along the old ,one as a pattern..

Admittedly, some time ago, but the last two that I boughtn were under £10 each

Howard

[BazyleParticipant @bazyle]

Does it actually play any part when running? isn't it just there on a starting winding to make the fan go in the right direction initially? Though if it is short circuit it might be causing drag.

[john fletcher 1Participant @johnfletcher1]

Usually these fans are Cap start and Run no centrifugal switch, the actual value be on on the can.

[John HaineParticipant @johnhaine32865]

Presumably capacitor start and run. Permanently connected.

[Grizzly bearParticipant @grizzlybear]

Electric Motor Run Capacitor 1.5uf – 100uf mfd 400/450v Spade Terminal Fly Lead | eBay

Good luck, Bear……….

[Bill PhinnParticipant @billphinn90025]

Thanks a lot for everyone's replies.

I've given the lube some time to work its way down the shaft, and rotation speed seems to have increased somewhat. However, it still seems slower than normal [even in the warmth of indoors], so I'm not convinced the capacitor isn't faulty.

Do I take it I can't test the capacitor unless it's desoldered, or unless I have an ESR meter, which I don't?

[Andrew TinsleyParticipant @andrewtinsley63637]

There are some surprisingly cheap and accurate capacity meters available on Ebay. Checked mine against a very expensive capacity meter and there is little if any difference in results! It takes all of the guessing out of the equation.

Andrew.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Bill, to get an accurate reading you should take it out of circuit, even if it is only one side that is disconnected, and like Andrew says, there are many low priced multi-meters with a capacity range, but you must insure there is no residual charge in the capacitor before testing it.

Regards Nick.

[John HaineParticipant @johnhaine32865]

Frankly I'd just buy a new one, it would be cheaper than buying a meter! The link that Bill posted has them at £6.71 for 1.5uF. RS list 1uF at £6.43.

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