Randall TR3driver at ca.rr.com
Thu May 17 08:30:46 MDT 2018

> tr-3 with crane electronic ignition.  Went to negative ground and
> alternator this past winter.  Was also running fine on first run this
> spring.  Last time out started missing.  Have not had time to get into it
> seriously but just wanted to know about the led light on the modem.  Will
> it blink to show trouble inside the modem or keep showing solid light?
> Also when they fail to they fail completely or limp along missing for a
> while?

As usual, not that simple.  The LED blinks to show that the module received
a signal from the optical pickup; but really says nothing about whether the
signal is correct (edge happens at right time to fire plugs).  All you can
really say is that if the LED does not blink at all (with the engine turning
slowly), there is a problem with either power to the module, or the signal
from the pickup (which in turn could be a problem with the pickup itself,
wiring to it, or the part of the module that receives the signal).

Yes, it is quite possible for either the module itself, or the connections
to it; to fail gradually.

Something to watch out for: some ignition rotors stick out on the side
opposite the contact and can interfere with the optical pickup. Eg,
(That's just a sample image I found on the web, my rotor actually said
'Lucas' on it.)

In my case, it only lightly contacted the pickup, no physical damage was
apparent.  But apparently it would vibrate badly enough to cause
intermittent operation.  Furthermore, the problem came and went to the
extent that I thought I had fixed it several times.  I even took off for VTR
2000 (1000 miles each way) with it in place; and had to stop to convert back
to points when it started acting up again.

Another problem I had (later, after solving the rotor problem, tweaking the
phasing and so on) was corrosion in the joint between the ground wire and
the body.  That was also a gradual failure, I had noticed it wasn't running
quite right for a few days, but then it suddenly got much worse (naturally
while driving home from work in the rain).

> Just would like to know what the signs are on the modem.  If i know right
> away if its the modem or not it might save looking every where else.

Check your instructions, there is a short trouble-shooting section near the
end.  There should be a copy available on the Crane Cams website (if you
have misplaced yours); but Google told me just now it may have been hacked,
so caution is probably advised.  I posted a copy (which may be outdated) at

-- Randall 
56 TR3 TS13571L once and future daily driver
71 Stag LE1473 - awaiting engine rebuild
71-2-3 Stag - awaiting gearbox rebuild

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