> I'm troubleshooting a lack of spark on my TR3A and wondered if anyone knew
> the approx. capacitance of the condensor?
I believe it's around 1 microfarad when new. Somehow I've got it stuck in
my head that it will work with as little as 0.33 mfd, but I wouldn't trust
that.
> Any likelyhood of getting a reasonable capacitance reading from a
> condensor
> that would still not function well on the car?
I'd say it's certainly possible, although I haven't really done a study of
how automotive condensers fail. But a decent tester should be able to read
capacitance hundreds if not thousands of times smaller than what it takes to
make the ignition work, and it's not at all unusual for capacitors to go
down in capacitance as they age. Another question is how much leakage is
allowable ...
I've read somewhere that one check for a duff condenser is to watch the
points for sparks as you crank the engine. The purpose of the condenser is
to prevent the spark jumping the gap as the points open, so it makes sense
to me. Unfortunately, I didn't know this when I had my one and only
condenser failure many years ago, so I've never tested the theory. I
certainly see sparks when opening the points by hand, but that's probably
because I don't open them fast enough or something.
> For that matter, is checking the coil with an inductance meter likely to
> mean much?
Would certainly be valuable if you had "before and after" readings. But I
don't know how large the variation is between different models of coil ...
presumably "high output" coils have more inductance, but probably still
wouldn't work if they had enough turns shorted to reduce the inductance
readings to "standard coil" levels.
> What range inductance should I expect to see?
According to an old article from Dan Masters, about 6-10 millihenrys.
Another article gives it as "7.5-8.6 mH", but it's not clear which coil they
are talking about.
Frankly, it's far easier to test those components by substitution. There's
no reason the condenser has to be inside the dizzy for a test. The
components from a VW bug (or similar) will work fine and should be readily
available. Not sure if the bug condenser had a long lead, but the VW Rabbit
I owned for awhile certainly did.
Next time you do a tune-up, save the old condenser for testing. IMO a spare
coil is a good idea, too.
Randall
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