In article ,
lardconcepts writes:
There's a pump which boosts pressure to the cold circuit (taps, bog
etc) in our house when a tap is turned on.
About 1 time in 5, it won't spin, but just sit there humming. As I
suspected, the electric meter spins pretty quickly when it's stuck
like this!
The main plate on top says:
OSIP Electropompe Tpe VCB45/42
0.33Kw 220-240v 2.5a 8µF
Vc:450 Hz:50 IS.CL:F
Inside, there's a capacitor. It says:
Italfarad - 05/90 (date of manufacture, I'd guess)
RP-3 10040
µF: 10 ±5%b
450V~ DB HPFPU
400V~ DB HPFNT
------------------------------
500V 120/10
400V H250 25/85 360V
So, there it all is! Do capacitors fade over time?

Yes, although it's sometimes obvious due to the guts spewing out.
The capacitor failing will result in reduced (and eventually no)
starting torque.

Anyway of testing with yer standard £5 Maplin yellow multimeter?

Yes (actually, don't even need a meter).
Impedance of an 8µF capacitor is about 400 ohms (at 50Hz).
That's also about the resistance of a 150W mains light bulb.
Temporarily remove the capacitor from the motor. Find a 60W
or 100W light bulb (filament), and wire it up to the mains in
series with the capacitor. (If the capacitor has a metal case,
for safety's sake, assume it could be live during the test.)
The bulb should light up at significantly reduced brightness,
and if left on for a while, the capacitor should not get hot.
The capacitor is dead if the light doesn't light at all, lights
at full brightness, or the capacitor gets very hot.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]