capacitor testing question

[RichK]

I have a broken small appliance (food processor) where I think the problem
may be with the motor start capacitors. When I try to use the unit, there
is a buzz, but the motor doesn't run. There are 2 capacitors labeled "motor
start". Both are rated for 170 VIC. One is 100 mF; the other is 130 mF.
All I have for testing is a digital multi-meter. When I test both of the
capacitors on a high-resistance scale, they seem to pass current for about
15 seconds. (On the 200k ohm scale, the resistance slowly rises until it
shows "open".) Does this mean that they are bad? Is there any other thing
I can test without a capacitor meter?

 

[Andrew Holme]

RichK wrote:

I have a broken small appliance (food processor) where I think the
problem may be with the motor start capacitors. When I try to use
the unit, there is a buzz, but the motor doesn't run. There are 2
capacitors labeled "motor start". Both are rated for 170 VIC. One
is 100 mF; the other is 130 mF. All I have for testing is a digital
multi-meter. When I test both of the capacitors on a high-resistance
scale, they seem to pass current for about 15 seconds. (On the 200k
ohm scale, the resistance slowly rises until it shows "open".) Does
this mean that they are bad?

No, on the contrary: it's normal. You're charging the capacitor up.
Current slows and finally stops as the voltage on the capacitor approaches
that of your multimeter. Try measuring the voltage across the capacitor
afterwards: you'll see it discharge through the meter.

 

[Jerry G.]

To know if the cap is on value, you need a capacitor testing meter, or such
a scale on your volt meter. To see if the cap is functioning properly under
working conditions, a capacitor ESR meter is required. The only other
reliable way to test them, is to change them.

It is also possible that the motor is defective. I have seen defective
motors in appliances from time to time.

--

Jerry G.
======


"RichK" <NOSPAM@nospam.com> wrote in message
news:YgcHd.12208$wZ2.5180@newssvr13.news.prodigy.com...
I have a broken small appliance (food processor) where I think the problem
may be with the motor start capacitors. When I try to use the unit, there
is a buzz, but the motor doesn't run. There are 2 capacitors labeled "motor
start". Both are rated for 170 VIC. One is 100 mF; the other is 130 mF.
All I have for testing is a digital multi-meter. When I test both of the
capacitors on a high-resistance scale, they seem to pass current for about
15 seconds. (On the 200k ohm scale, the resistance slowly rises until it
shows "open".) Does this mean that they are bad? Is there any other thing
I can test without a capacitor meter?

 

[Miles Harris]

On Tue, 18 Jan 2005 18:08:56 GMT, "RichK" <NOSPAM@nospam.com> wrote:

One is 100 mF; the other is 130 mF.

I doubt it. Have a better look; you should replace them (if necessary)
with the correct values.

 

[RichK]

Sorry. The item "170 VIC" should read "170 VAC". My spell-checker "fixed"
it thinking that I had spelled Vic's name wrong.
"RichK" <NOSPAM@nospam.com> wrote in message
news:YgcHd.12208$wZ2.5180@newssvr13.news.prodigy.com...

I have a broken small appliance (food processor) where I think the problem
may be with the motor start capacitors. When I try to use the unit, there
is a buzz, but the motor doesn't run. There are 2 capacitors labeled
"motor start". Both are rated for 170 VIC. One is 100 mF; the other is
130 mF. All I have for testing is a digital multi-meter. When I test both
of the capacitors on a high-resistance scale, they seem to pass current for
about 15 seconds. (On the 200k ohm scale, the resistance slowly rises
until it shows "open".) Does this mean that they are bad? Is there any
other thing I can test without a capacitor meter?