Is the capacitor the same as the diode? or is the diode internal?

A capacitor is to a diode what a muffler is to a fuel injector. One is essential to output; the other just keeps the noise down.

From what I've been reading the capacitor in an alternator
has three diodes and a ground. Ohm resistance should only flow in only one direction
across the diodes. The capacitor turns AC current to DC current.
Please correct me if I'm wrong.

Are you saying that an alternator doesn't need a capacitor?
Also, that doesn't answer my question about whether or not I
need to take the alternator apart to check the diodes in the capacitor.

Thanks,
Jeff

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1984 300SD 300,000 miles--two tank WVO setup
2.88 diff & 500SEL anti-squat rear end

You are wrong.
Diodes convert ac to dc. Capacitors just smooth out the spikes.
There are no diodes in the capacitor.
Who ever is giving you the story about the capacitor is pulling your leg.
Best you go see a good auto elec or read a book on basic electronics.

__________________
Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

The word you are looking for is Rectifier.
http://en.wikipedia.org/wiki/Rectifier

I don't know if a bad capaciter could cause a charging issue (like a short circuit) but it could be unplugged to see what happens.
I don't recall my Alternator having a Capacitor.

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84 300D, 82 Volvo 244Gl Diesel

Easiest way to check out the diodes is with the to use a multi tester. Use the continuity setting, and with the alternator disconnected, touch one lead to the alternator connection that the battery wire is usually connected to, and with the other lead, touch the alternator case. If you have continuity, one or more of your diodes is failing.

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96 E300d