[MV] Dodge M37 Coil Resistance

Alan Bowes (inbox@todacosa.com)
Sun, 06 Sep 1998 17:42:16 -0600

I'm currently rebuilding two M37 distributors (at least they're
SUPPOSEDLY M37 distributors). One is an Auto-Lite and the other is a
Bendix. Both appear identical, except that one has a coil that is
stamped "24V" and the other distributor has a coil with no numbers at
all. Checking these coils with a meter shows that they are NOT the same.
The "24V" coil reads 12.2 ohms across the primary terminals and the
unmarked coil reads 6.1 ohms (exactly half). This leads me to believe
that the 6.1-ohm coil might be a 12V coil that was designed to be used
with a 24V system in conjunction with an external ballast resistor that
is bypassed during starting to avoid a weak spark while cranking the
engine.

I've looked at M37 and M37B1 wiring diagrams and can't find an ignition
resistor circuit. So, I'm thinking that one of these distributors may
have come from a different 24V M-series vehicle that used an ignition
resistor circuit. Any ideas? I'd like any information that anyone might
have on this subject. I'm writing an article on M37 distributor overhaul
and I'd like it to be as complete as possible.

Incidentally, if a bunch of 6.1-ohm coils have been mixed up with
12.2-ohm coils at some parts suppliers, it could explain things like
heat-related coil failures, points that burn out too quickly, etc.

It also suggests that someone who is interested in 24-to-12V conversions
might be able to install a 6.1-ohm coil and keep the stock distributor.

Both of these coils seem to produce a good spark when tested, and there
is no sign of any damage, corrosion, or leakage, so I assume that these
are good coils and that the resistance values are correct. However, I'd
like to verify this, so if it's convenient, perhaps some of you could
check a coil or two. Disconnect either (or both) of the coil's primary
leads, then read the resistance across the primary terminals with a good
meter and post the results.

The number on the marked 24V coil is CT-4002 24V 7G (Auto-Lite). This is
the 12.2-ohm coil.
The other coil has no numbers at all (Superior Magneto Corporation).
This is the 6.1-ohm coil.

Both of the distributor bodies are marked "Ignitor 24V", but one is by
Auto-Lite and the other is by Bendix.

Thanks,

Alan

===
To unsubscribe from the mil-veh mailing list, send the single word
UNSUBSCRIBE in the body of a message to <mil-veh-request@skylee.com>.