Comp motor, cap advice please

[Chipper]

Hi all, it's been a while, I hope everyone's OK... I've been quietly getting on with stuff but got a dilemma. I've got a 3hp comp from the mid 90s, make unknown as it came from Shiremoor as recon and he painted the whole thing in Hammerite...

I've wanted to replace the start/run caps. The motor plate (Brook Hansen) says MFD 30/200, so that's what I bought, before testing the ones on it (one cap is not obviously blown or bad visually, but the end cap is loose/coming off). So one cap measures 28uF, close enough to expected. The other, with the end cap coming off, measures 418uF...

Can caps go higher in capacitance when they start going bad..? Otherwise I'm foxed why someone would put a ~400uF cap when the plate calls for 200 ... I'd fit the new 200uF but nagging doubt says seek advice... Cheers.

 

[Turbo]

30/200 sounds about right for a 3hp motor, 418uf is much too high. Are you testing them with a proper capacitance test meter? What do the new ones test at? If they are the Chinese ones from ebay you might find that they can be 1 or 2 uf out!

 

[Chipper]

The new ones come from RS Components and from an Abac parts supplier . Tested with a Draper auto-ranging digital meter, it's been good with the far tinier caps I normally mess with in guitar/pedal electronics, the new comp caps test close to the rated value.
Thanks for the confirmation, I'll go with the 200 then. I was foxed at the 400+ reading but don't know whether to expect rise in capacitance with age or if there'd be some reason for fitting a large one to it.

 

[carbon]

When caps deteriorate they tend to loose capacitance rather than gain it