GM HEI circa 1985 info needed

[Don.F.Broadus at ucm.com]

>From the 1987 Chevy light truck manual the 2.5L S/T truck distributor has a
regular HEI pickup coil and a Hall effect switch mounted above the pickup
coil. The hall effect switch supplies reference pulses to the ECM and tells
it which
Cylinder is next to fire. The 2.5L S/T HEI module is a 7 terminal module but
the 'R' (reference) is not connected.
The hall effect switch has 3 terminals A/B/C  A goes to +12 volts 'B ' is
the output and swings from 0 volts to almost 12 volts when a metal blade is
placed in the gap. 'C' is ground.  All of the hall effects I have seen need
+12/out/ground
So your 2 wire could be a coil. I would not use the output of a hall effect
to trigger a module, the 12 volts could damage it. 




-----Original Message-----
	From:	Mike Morrin [SMTP:mikem at southern.co.nz]
	Sent:	Tuesday, October 27, 1998 11:54 AM
	To:	diy_efi at efi332.eng.ohio-state.edu;
diy_efi at efi332.eng.ohio-state.edu
	Subject:	Re: GM HEI circa 1985 info needed

	At 09:19 pm 10/26/98 -0800, Stowe, Ted-SEA wrote:
	>
	>hi, I am working on building a mutant Lucas/gm distributor for my
mg tbi
	>project.
	>
	>I have a '85 tbi system from a sunbird, which uses a HEI
distributor.
	>
	>I have the matching GM ignition module which would of gone into
that set-up.
	>and I have a Lucas distributor which uses a hall effect sensor,
which fits
	>into my block.
	>
	>my problem is that the Lucas sensor has a 3 wires coming out of it,
whereas
	>the gm hall effect sensor uses 2. 

	Did GM use hall effect?  I thought the HEI systems used reluctors,
and do
	not work properly if triggered by a square wave.

	FWIW 

	Mike